How to mount rafters on a gable roof. Types and schemes of truss systems: an overview and recommendations for the installation of a roof truss system. Do-it-yourself design features of a gable roof

Reading time ≈ 10 minutes

The most common option in the construction of private houses is a gable roof, assembled with your own hands from the Mauerlat to the ridge. Below in this article you will find drawings and photos, and detailed step-by-step instructions will help you understand them. You will also learn how high the ridge should be and how it depends on the functionality of the attic, learn how to calculate the thickness and pitch of the truss system.

Classic gable roof

What are the roofs

The main types of roofs of private houses

In order to clearly imagine what a gable roof is, look at what other options are used in the construction of private houses. And this is not all, but the most popular:

- the easiest coating option for construction in the private sector. It is mainly used for country houses and utility rooms.
Gable - the most common option for country houses. Despite the apparent simplicity, this type is very practical and beautiful in execution.
Hip - more suitable for houses with a large area. This design is able to withstand very strong wind loads, up to a storm, thanks to the streamlined shape.
Half hip - this option is done more for beauty, as this is a prototype of a gable roof with cut corners from the ends of the ridge.
Hipped - pyramidal shape is suitable for square buildings. In fact, this is a prototype of a hip roof.
Vaulted - rarely used for residential construction, although it is no exception.

For a rectangular house with an area of 60 to 100 m2, the two-slope option can be called the most suitable - it is easy to perform and inexpensive to implement. In addition, there you can equip not only the attic, but also the attic.

Stages of construction of a gable roof

Now let's figure out how to build a gable roof system in a private house. There are several stages in this process, and we will consider each of them separately.

Calculation of the truss system, taking into account the existing loads

You can not use the formulas for the calculation if you do not make roofs in the future and just download the program (http://srub-banya.by/programs/raschet_stropil.exe). By opening the downloaded file, you will be taken to a page with a menu - it is located in the horizontal line at the top.

Main operating loads:

Snow cover.
Wind pressure.

In addition to the main loads, there are also secondary or “default” ones, these are:

Weight of roofing material.
Mass of insulation (if provided).
Own weight of the truss system.

Values:

S is the load value in kg/m2.
µ is the coefficient corresponding to the slope angle.
Sg - snow load standard in kg / m2.

The slope of the slope is expressed in degrees and is denoted by the symbol α (alpha). To determine the value of α, you need to divide the height H by half the span L. Below is a table with the results of determining the main slopes.

In cases where:

α≤30⁰, µ=1;
α≥60⁰, µ=0;
30°<α<60°, µ = 0,033*(60-α).

Distribution of snow loads in Russia

The map shows eight snow regions, and the Sg value for each is calculated in kPa converted to kg/m2:

I - 0.8 kPa = 80 kg/m2;
II - 1.2 kPa = 120 kg / m²;
III - 1.8 kPa = 180 kg / m²;
IV - 2.4 kPa = 240 kg / m²;
V - 3.2 kPa = 320 kg / m²;
VI - 4.0 kPa = 400 kg / m²;
VII - 4.8 kPa = 480 kg / m²;
VIII - 5.6 kPa = 560 kg / m².

For the map above, Appendix 5 of SNiP 2.01.07-85 "Loads and Impacts" is mandatory. And now let's make a trial calculation for Ivanovo (this is the IV district on the map), the value is 240 kg / m².

So: H/L=2.5/3.5=0.714

According to the table α=35⁰. Given that 30°<α<60°, вычисление µ делаем по формуле µ = 0,033·(60-α)=0,033*(50-35)=0,825. Следовательно, S=Sg*µ=240*0,825=198 кг/м², что и есть максимально возможной снеговой нагрузкой.

Wind loads

At steep roofs, where α > 30 °, then the slopes have a large windage. For flat roofs, where α< 30° увеличена турбулентность.

The average value of the wind load Wm at a height Z above the ground is calculated by the formula Wm=Wo*K*C.

In this formula, the value;

Wo is wind pressure;
K is the coefficient of change in wind pressure relative to height;
C is the aerodynamic coefficient.

Wind loads on the territory of the former USSR

Wind pressure standards by region

Coefficient value

Let's make a conditional calculation . The aerodynamic coefficient C can be from -8 when the wind undermines the roof to +0.8 with a large windage (the wind presses on the slope). Considering the conditionality of the calculation, we take C = 0.8.

In the same Ivanovsky district, we take a house where h=6m (α=35⁰). This is region II, where Wo= 30 kg/m², the coefficient is less than 10, which means K=1.0. Therefore: Wm=Wo*K*C=30*1*0.8=24 kg/m².

Roof weight

The mass of the roof varies depending on material

Mass of all components

The conditional calculation for the same house on cement-sand tiles will be:

And here is the calculation for the lightest roofing material, metal tiles:

We calculate the truss system

In this case, we will be guided by GOST 24454-80 for conifers.

Section width (according to the thickness of the board), B	Section height (along the width of the board), H
16	75	100	125	150	—	—	—	—	—
19	75	100	125	150	175	—	—	—	—
22	75	100	125	150	175	200	225	—	—
25	75	100	125	150	175	200	225	250	275
32	75	100	125	150	175	200	225	250	275
40	75	100	125	150	175	200	225	250	275
44	75	100	125	150	175	200	225	250	275
50	75	100	125	150	175	200	225	250	275
60	75	100	125	150	175	200	225	250	275
75	75	100	125	150	175	200	225	250	275
100	—	100	125	150	175	200	225	250	275
125	—	—	125	150	175	200	225	250	—
150	—	—	—	150	175	200	225	250	—
175	—	—	—	—	175	200	225	250	—
200	—	—	—	—	—	200	225	250	—
250	—	—	—	—	—	—	—	250	—

We take an arbitrary section width and determine the height:

H ≥ 8.6*Lmax*√(Qr/(B* Rbend)), where slope α< 30°,

H ≥ 9.5*Lmax*√(Qr/(B*Rbend)), where Rbend e slope α > 30°.

Values:

H is the height of the section, cm;
Lmax - rafter leg of maximum length, m;
Qr - distributed load per meter of rafter leg, kg / mr;
B- section width, cm.

For softwood sawn timber Rbend:

Grade I - 140 kg / cm²;
II grade - 130 kg / cm²;
III grade - 85 kg / cm².

Now let's check whether the deflection will fit into the standard, which for all materials under load should not exceed the value L / 200 (L is the length of the working section of the leg). The indicator must correspond to the inequality: 3.125*Qr*(Lmax)³/(B H³) ≤ 1.

Meaning:

Lmax is the working section of the leg of maximum length, m;

B is the width of the section, cm;

H is the height of the section, cm.

We count on the same house in Ivanovo, taking into account the conditions where:

slope α=35⁰;
rafter pitch A = 0.8 m;
working section of the leg Lmax=2.8 m;
pine timber of the 1st grade Rbend = 140 kg/cm2;
cement-sand tiles 50 kg/m2.

In the table above we have calculated that with these materials the total load is Q=303 kg/m².

we calculate the load per running meter of the leg: Qr=A*Q= 0.8*303=242 kg/m running.
Let's take a board thickness of 5 cm and calculate the cross section along the height: it means: H ≥ 9.5*Lmax* √(Qr/B*Rbend), since the slope α>30°. H≥9.5*2.8*√(242/5*140)=15.6 cm. Based on the table, the board with the nearest section will be 5×17.5 cm.
We check the inequality: 3.125*Qr*(Lmax)³/B*H³≤1 or 3.125*242*(2.8)³*5*(17.5)³=0.61<1.

As a result, we got a cross section of rafters for erecting a roof of 50 × 175 mm with a step of 80 cm.

Mauerlat installation

Mauerlat on a brick wall

To build a gable roof on your own, you can’t do without a Mauerlat, which is the basis of the truss system. If we are talking about a residential building, then a bar with a section from 50 × 150 mm to 150 × 200 mm is usually used for it (the thicker the wall, the larger the section of the bar in width). A board or beam is mounted on load-bearing walls and fixed with anchors. Given that the Mauerlat will withstand the entire truss system with associated loads, then its installation will directly affect the mechanical strength of the entire roof. Below is a video showing how a Mauerlat is installed on the walls of a block house.

Video: Installing the Mauerlat

Assembling the truss system

Rafter legs are easier to assemble on the ground

A structure such as rafters (2 legs plus additional elements) is most conveniently assembled on the ground, as in the photo above, and not on the roof, so that later it can be lifted with blocks or just ropes, but this is not a requirement. Above, you could learn how to make calculations for such a system, taking into account all the loads, therefore, you already know what section of the boards you will need, what the height of the ridge and the step size will be. At the top, the boards are joined “on the mustache”, and the ridge beam is installed only after the installation of the extreme rafters.

A system without an overhang, where the legs are fixed with different fasteners

Systems with an overhang also have different fasteners.

At the top you see two diagrams showing truss systems without overhang and with overhang, but the most important thing is to pay attention to the method of fastening, or rather, to the fastener itself. This can be a steel corner (preferably reinforced), short stacks, tightening boards, nails, self-tapping screws and staples. This is a very important point, since during turbulence the roof can be blown up, and overturned with a side load, although the result in both cases will be equally deplorable. After installing the side rafters, the ridge beam is fixed, checking the vertical level of each leg.

Watch the video, which explains some of the nuances of editing, but do not forget that each artist may have their own methods, and if you hear or see inconsistencies with your ideas, then this is quite normal.

Video: Installation of the truss system

Roof

Installation of ceramic tiles

Further work on the installation of the truss system depends on what is provided in the attic and what roofing material will be used. For example, if you want to equip an attic there, then it is quite natural that you cannot do without insulation and waterproofing. Also, a certain role will be played by the heating system, or rather, the presence or absence of a chimney, as well as ventilation.

Depending on the choice of roofing material, a crate is made. That is, it can be intermittent, as in the top photo, or solid if you decide to make a roof from shingles. Also, roofs sometimes provide for the installation of a heating cable from icing, and it can be mounted not only from the outside, but also from the inside, laying under the roof.

Conclusion

I hope you understand how to make a gable roof with your own hands - the most important thing is the correct calculations of the pitch, section of the rafter legs and slope. If you are interested in certain points, such as mounting the Mauerlat, rafters or roofing, then these are topics for separate articles, which you can also find on our website.

At the heart of each roof is a large number of beams, rafters, racks and girders, which are collectively called the truss system. Over the centuries-old history of types and methods of its organization, a lot has accumulated, and each has its own characteristics in the construction of knots and cuts. We will talk in more detail about what the gable roof truss system can be and how the rafters and other elements of the system should be attached in more detail.

The design of the gable roof truss system

In the context of a gable roof is a triangle. It consists of two rectangular inclined planes. These two planes are connected at the highest point into a single system with a ridge beam (run).

Gable roof scheme

Now about the components of the system and their purpose:

Mauerlat - a timber that connects the roof and walls of the building, serves as a support for the rafter legs and other elements of the system.
Rafter legs - they form the inclined planes of the roof and are the support for the crate under the roofing material.
Ridge run (bead or ridge) - combines two roof planes.
Puff - a transverse part that connects opposite rafter legs. Serves to increase the rigidity of the structure and compensate for bursting loads.
Beds - bars located along the Mauerlat. Redistribute the load from the roof.
Side runs - support the rafter legs.
Racks - transfer the load from the runs to the beds.

Filly may still be present in the system. These are boards that extend the rafter legs to form an overhang. The fact is that in order to protect the walls and foundation of the house from precipitation, it is desirable that the roof ends as far as possible from the walls. To do this, you can take long rafter legs. But the standard lumber length of 6 meters is often not enough for this. Ordering non-standard is very expensive. Therefore, the rafters are simply grown, and the boards with which this is done are called “fillies”.

There are quite a few designs of truss systems. First of all, they are divided into two groups - with layered and hanging rafters.

The difference in the design of layered and hanging rafters

With hanging rafters

These are systems in which the rafter legs rest only on the outer walls without intermediate supports (bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a strut system, it can be increased up to 14 meters.

The hanging type of gable roof rafter system is good because in most cases there is no need to install a Mauerlat, and this makes the installation of rafter legs easier: no need to make cuts, just mow the boards. To connect the walls and rafters, a lining is used - a wide board, which is attached to studs, nails, bolts, crossbars. With such a structure, most of the bursting loads are compensated, the impact on the walls is directed vertically downwards.

Types of truss systems with hanging rafters for different spans between load-bearing walls

Gable roof truss system for small houses

There is a cheap version of the truss system when it is a triangle (photo below). Such a structure is possible if the distance between the outer walls is not more than 6 meters. For such a rafter system, it is possible not to calculate the angle of inclination: the ridge must be raised above the puff to a height of at least 1/6 of the span length.

But with this construction, the rafters experience significant bending loads. To compensate for them, they either take rafters of a larger section or cut the ridge part in such a way as to partially neutralize them. To give greater rigidity in the upper part, wooden or metal plates are nailed on both sides, which securely fasten the top of the triangle (also see not the picture).

The photo also shows how to grow rafter legs to create a roof overhang. A notch is made, which should go beyond the line drawn from the inner wall upwards. This is necessary to move the incision site and reduce the likelihood of a rafter breaking.

Ridge knot and fastening of rafter legs to the backing board with a simple version of the system

For mansard roofs

The option with the installation of a crossbar is used when organizing a dwelling under the roof - an attic. In this case, it is the basis for filing the ceiling of the room below. For reliable operation of this type of system, the crossbar notch must be hingeless (rigid). The best option is semi-pan (see the picture below). Otherwise, the roof will become unstable to loads.

Gable roof truss system with raised tightening and crossbar cutting unit

Please note that in this scheme there is a Mauerlat, and the rafter legs should extend beyond the walls to increase the stability of the structure. To secure them and dock with the Mauerlat, a cut is made in the form of a triangle. In this case, with an uneven load on the slopes, the roof will be more stable.

With such a scheme, almost the entire load falls on the rafters, therefore they must be taken with a larger section. Sometimes the raised puff is reinforced with a suspension. This is necessary to prevent it from sagging if it serves as a support for ceiling sheathing materials. If the puff is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such insurances. In this case, boards and nails are also enough.

For big houses

With a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.

Large span gable roof truss system and ridge and rafter cutting units

With such a long span (up to 14 meters), it is difficult and expensive to make a one-piece puff, because it is made from two beams. It is connected by a straight or oblique cut (picture below).

Straight and oblique cut for tightening connection

For reliable docking, the junction is reinforced with a steel plate mounted on bolts. Its dimensions must be larger than the dimensions of the cut - the extreme bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the cut.

In order for the circuit to work properly, it is necessary to correctly make the struts. They transmit and distribute part of the load from the rafter legs to the puff and provide structural rigidity. Metal strips are used to reinforce the connections.

Fastening struts for the rafter system with hanging rafters

When assembling a gable roof with hanging rafters, the cross-section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore, each element has a greater load.

How the mansard roof is arranged (with drawings and diagrams) read here.

With rafters

In gable roofs with layered rafters, their ends rest on the walls, and the middle part rests on load-bearing walls or columns. Some schemes burst walls, some do not. In any case, the presence of a Mauerlat is mandatory.

The simplest version of layered rafters

Bezporny schemes and knots of cuts

Houses made of logs or timber do not respond well to spacer loads. For them, they are critical: the wall can fall apart. For wooden houses, the gable roof truss system must be non-expansion. Let's talk about the types of such systems in more detail.

The simplest non-spacer scheme of the truss system is shown in the photo below. In it, the rafter leg rests on the Mauerlat. In this embodiment, it works on a bend, without bursting the wall.

Simple non-branched gable roof system with rafters

Pay attention to the options for attaching the rafter legs to the Mauerlat. In the first, the support platform is usually beveled, while its length is no more than the cross section of the beam. Cutting depth - no more than 0.25 of its height.

The top of the rafter legs is laid on the ridge beam without fastening it to the opposite rafter. Two shed roofs are obtained according to the structure, which adjoin (but do not connect) one with the other in the upper part.

It is much easier to assemble the option with rafter legs fastened in the ridge part. They almost never give a thrust on the walls.

Mounting option for rafters without spreading on the walls

For this scheme to work, the rafter legs below are attached using a movable joint. To fix the rafter leg to the Mauerlat, one nail is hammered from above or a flexible steel plate is placed from below. See the photo for options for attaching rafter legs to a ridge run.

If the roofing material is planned to be heavy, it is necessary to increase the bearing capacity. This is achieved by increasing the cross section of the elements of the truss system and strengthening the ridge assembly. It is shown in the photo below.

Strengthening the ridge assembly for heavy roofing material or with significant snow loads

All of the above gable roof schemes are stable in the presence of uniform loads. But in practice, this almost never happens. There are two ways to prevent the roof from sliding in the direction of greater load: by installing a brace at a height of about 2 meters or by struts.

Options for truss systems with contractions

The installation of contractions increases the reliability of the structure. In order for it to work normally, at the places where it intersects with drains, you need to attach nails to them. The cross section of the beam for the scrum is used the same as for the rafters.

Schemes of truss systems of gable roofs with fights

They are attached to the rafter legs with bots or nails. Can be installed on one or both sides. The knot for attaching the bout to the rafters and the ridge run, see the figure below.

Fastening the scrum to the rafters and the ridge beam

In order for the system to be rigid and not “crawl” even under emergency loads, it is enough in this embodiment to provide a rigid fastening of the ridge beam. In the absence of the possibility of its displacement in the horizontal, the roof will withstand even significant loads.

How to make a gable roof (photo report) read here.

Rafter systems with braces

In these options, rafter legs, which are also called struts, are added for greater rigidity. They are installed at an angle of 45° with respect to the horizon. Their installation allows you to increase the span length (up to 14 meters) or reduce the cross section of beams (rafters).

The strut is simply substituted at the required angle to the beams and nailed from the sides and bottom. An important requirement: the brace must be cut accurately and fit snugly against the uprights and the rafter leg, excluding the possibility of its deflection.

Systems with rafter legs. Above is a spacer system, below is a non-spacer system. The nodes of the correct felling for each are located nearby. Below - possible strut mounting schemes

But not in all houses, the average load-bearing wall is located in the middle. In this case, it is possible to install struts with an angle of inclination relative to the horizon of 45-53 °.

Rafter system with off-center vertical purlin

Strut systems are necessary if significant uneven shrinkage of the foundation or walls is possible. Walls can sit differently on wooden houses, and foundations on layered or heaving soils. In all these cases, consider the installation of truss systems of this type.

System for houses with two internal load-bearing walls

If the house has two load-bearing walls, two rafters are installed, which are located above each of the walls. Beds are laid on the intermediate load-bearing walls, the load from the rafter beams is transferred to the beds through the racks.

Rafter Systems

In these systems, the ridge run is not installed: it gives expansion forces. The rafters in the upper part are connected to one another (cut and joined without gaps), the joints are reinforced with steel or wooden plates, which are nailed.

In the upper non-expansion system, the expanding force is neutralized by tightening. Please note that the puff is placed under the run. Then it works efficiently (the top diagram in the figure). Stability can be provided by uprights, or jointing - beams installed obliquely. In the spacer system (in the picture below), the crossbar is a crossbar. It is installed above the run.

There is a variant of the system with racks, but without rafters. Then a rack is nailed to each rafter leg, which rests with the second end on an intermediate load-bearing wall.

Fastening the rack and tightening in the rafter system without a rafter run

To fasten the racks, nails for 150 mm and bolts 12 mm are used. Dimensions and distances in the figure are in millimeters.

Rafters perform a number of significant roofing functions. They set the configuration of the future roof, perceive atmospheric loads, and hold the material. Among the rafter duties are the formation of even planes for laying the coating and providing space for the components of the roofing pie. In order for such a valuable part of the roof to flawlessly cope with the listed tasks, information about the rules and principles of its construction is needed. The information is useful both for those who are constructing the gable roof truss system with their own hands, and for those who decide to resort to the services of a hired team of builders.

Rafter structures for gable roofs

In the device of the truss frame for pitched roofs, wooden and metal beams are used. The starting material for the first option is a board, log, timber. The second is constructed from rolled metal: a channel, a profile pipe, an I-beam, a corner. There are combined structures with steel most loaded parts and wood elements in less critical areas.

In addition to the "iron" strength, the metal has a lot of disadvantages. These include heat engineering qualities that do not satisfy the owners of residential buildings. Disappointing need for the use of welded joints. Most often, industrial buildings are equipped with steel rafters, less often private change houses assembled from metal modules.

In the case of self-construction of truss structures for private houses, wood is a priority. It is easy to work with it, it is lighter, “warmer”, more attractive in terms of environmental criteria. In addition, nodal connections do not require a welding machine and welder skills.

Rafters - a fundamental element

The main "player" of the frame for the construction of the roof is the rafter, among the roofers called the rafter leg. Beds, braces, headstocks, girders, puffs, even Mauerlat may or may not be used depending on the architectural complexity and dimensions of the roof.

The rafters used in the construction of the gable roof frame are divided into:

Layered rafter legs, both heels of which have reliable structural supports under them. The lower edge of the layered rafter rests on the Mauerlat or on the ceiling crown of the log house. The support for the upper edge can be a mirror analogue of the adjacent rafter or a run, which is a beam horizontally laid under the ridge. In the first case, the truss system is called spacer, in the second, non-spacer.
hanging rafters, the top of which rests against each other, and the bottom is based on an additional beam - puff. The latter connects the two lower heels of adjacent rafter legs, resulting in a triangular module called a truss truss. The tightening dampens the tensile processes, so that only a vertically directed load acts on the walls. The design with hanging rafters, although it is spacer, does not transfer the spacer to the walls.

In accordance with the technological specifics of the rafter legs, the structures constructed from them are divided into layered and hanging. For structural stability, they are equipped with struts and additional racks. For the arrangement of supports for the top of the layered rafters, beds and girders are mounted. In reality, the truss structure is much more complicated than the elementary patterns described.

Note that the formation of a gable roof frame can generally be carried out without a truss structure. In such situations, the alleged planes of the slopes are formed by slegs - beams laid directly on the bearing gables. However, we are now specifically interested in the device of the gable roof truss system, and it can involve either hanging or layered rafters, or a combination of both types.

Subtleties of fastening rafter legs

The rafter system is fastened to brick, foam concrete, aerated concrete walls through the mauerlat, which in turn is fixed with anchors. Between the Mauerlat, which is a wooden frame, and the walls of these materials, a waterproofing layer of roofing material, waterproofing, etc. is necessarily laid.

The top of the brick walls is sometimes specially laid out so that something like a low parapet is obtained along the outer perimeter. So it is necessary that the Mauerlat placed inside the parapet and the walls do not burst the rafter legs.

The rafters of the frame of the roofs of wooden houses rest on the upper crown or on the ceiling beams. The connection in all cases is made by cutting and duplicated with nails, bolts, metal or wooden plates.

How to do without furious calculations?

It is highly desirable that the cross section and linear dimensions of the wooden beams be determined by the project. The designer will give clear calculation justifications for the geometric parameters of the board or beam, taking into account the entire range of loads and weather conditions. If there is no home design development master at his disposal, his path lies on the construction site of a house with a similar roof structure.

You can ignore the number of storeys of the building under construction. It is easier and more correct to find out the required dimensions from the foreman than to find them out from the owners of a shaky unauthorized construction. After all, the foreman is in the hands of documentation with a clear calculation of the loads per 1 m² of roof in a particular region.

The installation step of the rafters determines the type and weight of the roofing. The heavier it is, the smaller the distance between the rafter legs should be. For laying clay tiles, for example, the optimal distance between the rafters will be 0.6-0.7 m, and for the installation of metal tiles and profiled sheets, 1.5-2.0 m is acceptable. However, even if the step required for the correct installation of the roof is exceeded, there is a way out . This is a reinforcing counter-lattice device. True, it will increase both the weight of the roof and the construction budget. Therefore, it is better to deal with the step of the rafters before the construction of the rafter system.

Craftsmen calculate the pitch of the rafters according to the design features of the building, tritely dividing the length of the ramp into equal distances. For insulated roofs, the step between the rafters is selected based on the width of the thermal insulation boards.

On our site you can find a calculator for calculating a gable roof, which may also help you a lot during construction.

Rafter structures of layered type

Rafter structures of the layered type are much simpler in execution than their hanging counterparts. A justified plus of the layered scheme is to provide full ventilation, which is directly related to the longevity of the service.

Distinctive design features:

Mandatory presence of support under the ridge heel of the rafter leg. The role of the support can be played by a run - a wooden beam resting on racks or on the inner wall of the building, or the upper end of an adjacent rafter.
The use of Mauerlat for the construction of a truss structure on walls made of brick or artificial stone.
The use of additional runs and racks where the rafter legs, due to the large size of the roof, require additional support points.

The minus of the scheme is the presence of structural elements that affect the layout of the internal space of the operated attic. If the attic is cold and the organization of useful premises is not supposed to be in it, then the layered construction of the truss system for the installation of a gable roof should be preferred.

A typical sequence of work on the construction of a layered truss structure:

First of all, we measure the height of the building, the diagonals and the horizontalness of the upper cut of the skeleton. When identifying vertical deviations of brick and concrete walls, we eliminate them with a cement-sand screed. Exceeding the heights of the log house we squeeze. By placing chips under the Mauerlat, vertical flaws can be dealt with if their magnitude is insignificant.
The floor surface for laying the bed must also be leveled. He, the Mauerlat and the run must be clearly horizontal, but the location of the listed elements in the same plane is not necessary.
We process all wooden parts of the structure before installation with fire retardants and antiseptic preparations.
We lay waterproofing on concrete and brick walls for the installation of a Mauerlat.
We lay the Mauerlat beam on the walls, measure its diagonals. If necessary, we slightly move the bars and turn the corners, trying to achieve the perfect geometry. Align the frame horizontally if necessary.
We mount the Mauerlat frame. The splicing of the beams into a single frame is carried out by means of oblique cuts, the joints are duplicated with bolts.
We fix the position of the Mauerlat. Fasteners are made either with brackets to wooden plugs laid in the wall ahead of time, or with anchor bolts.
We mark the position of the bed. Its axis should recede from the Mauerlat bars at equal distances on each side. If the run will be based only on racks without lying down, the marking procedure is carried out only for these columns.
We install the bed on a two-layer waterproofing. We fasten it to the base with anchor bolts, connect it to the inner wall with wire twists or staples.
We mark the installation points of the rafter legs.
We cut out racks according to uniform sizes, because our bed is set to the horizon. The height of the racks must take into account the dimensions of the section of the run and the bed.
Installing racks. If provided by the project, we fix them with spacers.
We lay the run on the racks. We check the geometry again, then install the brackets, metal plates, wooden mounting plates.
We install a trial rafter board, mark the places of trimming on it. If the Mauerlat is set strictly to the horizon, there is no need to adjust the roof rafters in fact. The first board can be used as a template for making the rest.
We mark the installation points of the rafters. Folk craftsmen for marking usually prepare a pair of slats, the length of which is equal to the gap between the rafters.
According to the markup, we install the rafter legs and fasten them first at the bottom to the Mauerlat, then at the top to the run to each other. Every second rafter is screwed to the Mauerlat with a wire bundle. In wooden houses, the rafters are screwed to the second crown from the top row.

If the rafter system is done flawlessly, the layered boards are mounted in random order. If there is no confidence in the ideal structure, then the extreme pairs of rafters are installed first. A control twine or fishing line is stretched between them, according to which the position of the newly installed rafters is adjusted.

The installation of the truss structure is completed by installing the filly, if the length of the rafter legs does not allow the formation of an overhang of the required length. By the way, for wooden buildings, the overhang should “go beyond” the contour of the building by 50 cm. If the organization of the visor is planned, separate mini-rafters are installed under it.

Another useful video about the construction of a gable truss base with your own hands:

Hanging truss systems

The hanging type of truss systems is a triangle. The two upper sides of the triangle are folded by a pair of rafters, and the puff connecting the lower heels serves as the base. The use of tightening allows you to neutralize the effect of the spread, therefore, only the weight of the crate, the roof, plus, depending on the season, the weight of precipitation, acts on walls with hanging truss structures.

The specifics of hanging truss systems

Characteristic features of hanging type truss structures:

Mandatory presence of a puff, made most often of wood, less often of metal.
The ability to refuse the use of Mauerlat. A frame made of timber will be successfully replaced by a board laid on a two-layer waterproofing.
Installation on the walls of ready-made closed triangles - roof trusses.

The advantages of the hanging scheme include the space under the roof free from racks, which allows you to organize an attic without pillars and partitions. There are disadvantages. The first of these is the limitation on the steepness of the slopes: their slope angle can be at least 1/6 of the span of a triangular truss, steeper roofs are strongly recommended. The second disadvantage is the need for thorough calculations for the competent device of cornice nodes.

Among other things, the angle of the truss truss will have to be set with jewelry accuracy, because. the axes of the connected components of the hanging rafter system must intersect at a point, the projection of which must fall on the central axis of the Mauerlat or the lining board replacing it.

Subtleties of long-span hanging systems

Puff - the longest element of the hanging rafter structure. Over time, it, as is typical of all lumber, deforms and sags under the influence of its own weight. Owners of houses with spans of 3-5m are not too concerned about this circumstance, but owners of buildings with spans of 6 meters or more should think about installing additional parts that exclude geometric changes in tightening.

To prevent sagging in the installation scheme of the truss system for a large-span gable roof, there is a very significant component. This is a pendant called a grandmother. Most often, it is a bar attached with wooden surfs to the top of the truss truss. You should not confuse the headstock with the racks, because. its lower part should not come into contact with the puff at all. And the installation of racks as supports in hanging systems is not used.

The bottom line is that the headstock, as it were, hangs on a ridge knot, and a tightening is already attached to it with the help of bolts or nailed wooden plates. Threaded or collet type clamps are used to correct slack.

Adjustment of the tightening position can be arranged in the zone of the ridge knot, and the headstock can be rigidly connected to it with a notch. Instead of a bar in non-residential attics, reinforcement can be used to manufacture the described tightening element. It is also recommended to arrange a headstock or suspension where the puff is assembled from two bars to support the connection area.

In an improved hanging system of this type, the headstock is complemented by strut beams. The stress forces in the resulting rhombus are extinguished spontaneously due to the competent arrangement of the vector loads acting on the system. As a result, the truss system pleases with stability with a slight and not too expensive upgrade.

Hanging type for attics

In order to increase the usable space, the tightening of the rafter triangles for the attic is moved closer to the ridge. A perfectly reasonable move has additional advantages: it allows you to use puffs as the basis for filing the ceiling. It is attached to the rafters by cutting with a semi-frying pan with a duplication of a bolt. It is protected from sagging by installing a short headstock.

A noticeable drawback of the attic hanging structure is the need for accurate calculations. It is too difficult to calculate it on your own, it is better to use a ready-made project.

Which design is more cost effective?

Cost is an important argument for an independent builder. Naturally, the price of construction for both types of truss systems cannot be the same, because:

In the construction of a layered structure for the manufacture of rafter legs, a board or beam of small section is used. Because layered rafters have two reliable supports under them, the requirements for their power are lower than in the hanging version.
In the construction of a hanging structure, the rafters are made of thick timber. For the manufacture of puffs, a material similar in cross section is required. Even taking into account the rejection of the Mauerlat, the consumption will be significantly higher.

Saving on the grade of material will not work. For the bearing elements of both systems: rafters, purlins, beds, Mauerlat, attendants, racks, lumber of the 2nd grade is needed. For crossbars and puffs working in tension, you will need the 1st grade. In the manufacture of less responsible wooden slips, the 3rd grade can be used. Without counting, we can say that in the construction of hanging systems, expensive material is used to a greater extent.

Hanging trusses are assembled in an open area next to the object, then transported assembled upstairs. To lift weighty triangular arches from a bar, you will need equipment, for which you will have to pay rent. And the project for complex nodes of the hanging version is also worth something.

Video instruction on the installation of a truss structure of a hanging category:

There are actually many more methods for constructing truss systems for roofs with two slopes. We have described only the basic varieties that are actually applicable for small country houses and buildings without architectural ideas. However, the information provided is sufficient to cope with the construction of a simple truss structure.

Design options Rafter systems

Layered or hanging
Spacer or non-spacer
Mounting methods

Modern buildings sometimes amaze our imagination with the most unusual forms of roofs. They owe their stylish and spectacular appearance to the variety of truss structures. However, all of them are “assembled” in the skillful hands of the architect-designer, like a constructor, connected in a certain order from standard elements.

Design Options

The truss systems of pitched roofs depend on their features.

Shed- the easiest option to manufacture. The peculiarity of its design is the absence of a ridge, racks and struts. Such roofs, as a rule, cover buildings with 6-8-meter spans. Despite the simplicity of the design, With a reasonable approach, even such a simple design has its advantages. For example, on the south side, directed to the north, you can install fairly large windows. This is the most convenient truss system for an extension, garage, etc., especially since it allows you to "assemble" the roof from large-sized sheet materials.

Another simple and cheap design is gable. However, it is not without drawbacks either. For example, in a conventional roof of this type there is too little space for an attic.

hip- not two, but four-slope. From a certain angle, it resembles an ordinary gable. However, its slopes do not completely cover the surface of the house - the space remaining on the sides is closed by lateral triangular hips. Thus, the roof turns out to be hipped and two types of rafters are used for its construction.

Multi-forceps- this is a design, which, as it were, consists of a combination of gable roofs with multidirectional ridges. The truss system of such roofs is the most expensive, but it makes it possible to equip additional space in the attic.

Shatrovaya, due to its shape resembling a pyramid, it is maximally resistant to wind load. It also doesn't hold snow. And this despite the fact that her rafter system is one of the simplest. True, the absence of gables does not allow even a small room to be equipped in the attic.

Rafter systems

Layered or hanging

The frame for the device consists of triangular-shaped elements, due to which, even when experiencing a large number of variable loads, the structure does not lose rigidity. Rafter systems of pitched roofs are divided into hanging and layered.

The choice of one or another type, method of fastening is based on the following parameters:

the dimensions of the building itself;
the slope and shape of the roof;

Rafters

For buildings with a single or gable roof, the use of layered rafters is more common. This is a structure assembled from short bars or boards, which has two or three points of rigid attachment. In the first version, these are the walls of the building, in the case of a gable, a ridge is added, and the ridge beam in this case must be reinforced with racks. The supports for the latter are beds. The length of the rafters in buildings that are large in size exceeds 6 m. It is possible that additional support structures will need to be installed here. For example, to build inside the main walls or columnar supports.

hanging

This design is characterized by the absence of intermediate supports. Such rafters often cover spans exceeding 7 m. The wall remains the only reference point for the rafter leg. As for the second end, in this case, the upper parts of the rafter beam and the opposite leg are joined. For this, various methods are used: by means of a slotted spike or metal plates, a half-tree connection.

Spacer or non-spacer

The reliability of the roof, first of all, is ensured by a careful calculation of the loads under the influence of which its frame is located. Rafters become, as it were, "conductors" of these loads on the external supports of the structure. The load that the rafters exert on their supports is of two types - expansion and non-expansion.

Spacer

The rafter beams in this design work in compression and bending, which causes a significant horizontal expansion force. It is naturally transferred to the walls. When installing a horizontal puff, it will take on this spacer, and this force will decrease. This farm element performs several functions:

connects rafters,
serves as a support for them,
does not allow the bases of the beams to part.

The puff can be installed at the base of the rafters, then it will act as a floor beam. It can be set higher. With such a device, the tightening is called a crossbar. For large spans, as a rule, it is necessary to complicate the design of trusses, that is, they install not only puffs, but other additional elements.

thrustless

The support of the lower ends of the rafter legs in this system are:

walls, and with their upper ends they are connected to each other by a run, which, in turn, rests on racks or
support frames formed by top and bottom girders, uprights and struts

The elements of the system function like beams, that is, exclusively in bending.

Mounting methods

Thrustless systems. Rafters of this type are installed in such a way that one support turned out to be fixed, and the other - movable, and both of them should be able to rotate freely. In practice, there are three ways to eliminate dangerous loads that affect the walls in this case. The lower end of the rafter leg rests against the Mauerlat. It is hemmed with a bar and fixed using a cut with a tooth. It is also desirable to additionally insure the fastening with wire. The upper part of the beam is mounted on a ridge run. For fasteners use the principle of sliding support. An example is the rafter system of the veranda.

The bottom of the rafter is fixed using a movable joint. To fix the upper part after it is laid on the ridge run, use a bolt, nails, etc. This is the most common option for gable roofs.
Rigid fastening to the run with nails, studs or other fasteners.

In any version, the following principle is observed: at one end, the rafter leg is fixed on a support that operates on the principle of sliding, allowing rotation, and at the other, on a hinge that allows only rotation.

Spacers. Both supports, unlike non-thrust ones, are fixed. The installation is carried out according to the same construction schemes, only in this case the lower supports are fixed not on sliders, but on a hinge that allows one degree of freedom. Support bars about a meter long can be nailed to the bottom of the rafters, or the support is attached to the Mauerlat on the “tooth”.

For small light roofs, it can be arranged without a Mauerlat, however, it should be noted that in this case the load on the wall is unevenly distributed.

A gable roof or gable roof is a roof with two slopes, i.e. having 2 inclined surfaces (slopes) of a rectangular shape.

The gable roof frame, due to its design features, ideally combines ease of installation and maintenance with reliability and durability. These and many other parameters make the construction of a gable roof a practical and rational solution for private and commercial housing construction.

In this article, we will consider how to make a gable roof truss system with your own hands. For effective perception of the material, it is presented in the form of step-by-step instructions from A to Z, from selection and calculations, to installation of a Mauerlat and a crate under the roof. Each stage is accompanied by tables, diagrams, drawings, drawings and photos.

The popularity of the roof with a house is due to a number of advantages:

design variability;
simplicity in calculations;
natural flow of water;
the integrity of the design reduces the likelihood of leaks;
profitability;
preservation of the useful area of the attic or the possibility of arranging an attic;
high maintainability;
strength and wear resistance.

Types of gable roof

The installation of a gable roof truss system depends primarily on its design.

There are several options for gable roofs (types, types):

1. Simple gable roof - symmetrical

Simple gable roof - symmetrical The most common version of the roof device due to its simplicity and reliability. Due to the symmetry, a uniform distribution of loads on the load-bearing walls and the Mauerlat is achieved. The type and thickness of the insulation do not affect the choice of material.

The cross section of the beam makes it possible to provide a margin of bearing capacity. There is no possibility of bending the rafters. Supports and spacers can be placed almost anywhere.

A clear drawback is the impossibility of arranging a full-fledged attic floor. Due to sharp corners, “blind” zones appear that are unsuitable for use.

2. Simple asymmetrical gable roof

Simple asymmetric gable roofThe arrangement of one angle of more than 45 ° leads to a decrease in the amount of unused area. There is an opportunity to make living rooms under the roof. At the same time, the requirements for the calculation are increasing, because. the load on the walls and foundation will be distributed unevenly.

3. Broken gable roof, with external and / or internal fracture

Broken gable roof, with an external and / or internal break Such a roof construction allows you to equip a full-fledged second floor under the roof.

Naturally, a simple gable truss roof differs from a broken one, not only visually. The main difficulty lies in the complexity of the calculations.

The design of the gable roof truss system

Building a roof of any complexity with your own hands involves knowledge of the purpose of the main structural elements.

The locations of the elements are shown in the photo.

Elements of the truss system of a gable roof Elements of the gable roof truss system - scheme 2
Elements of the gable roof truss system - scheme 3

Mauerlat. Designed to distribute the load from the truss system to the load-bearing walls of the building. For the arrangement of the Mauerlat, a beam of durable wood is selected. Preferably larch, pine, oak. The cross section of the beam depends on its type - solid or glued, as well as on the estimated century of construction. The most popular sizes are 100x100, 150x150 mm.
Advice. For a metal truss system, the Mauerlat must also be metal. For example, a channel or an I-profile.

rafter leg. The main element of the system. For the manufacture of rafter legs, a durable beam or log is used. The legs connected from above form a farm.

The silhouette of the roof truss determines the appearance of the structure. Examples of farms in the photo.

Roof truss options

Rafter parameters are important. They will be discussed below.

puff- connects the rafter legs and gives them rigidity.

Run:

Skate run, mounted at the junction of one rafter to another. In the future, a roof ridge will be installed on it.

Side runs, they provide the truss with additional rigidity. Their number and size depend on the load on the system.

Rafter rack- vertically located beam. It also takes on part of the load from the weight of the roof. In a simple gable roof, it is usually located in the center. With a significant span width - in the center and on the sides. In an asymmetrical gable roof - the installation location depends on the length of the rafters. With a sloping roof and the arrangement of one room in the attic attic, the racks are located on the sides, leaving free space for movement. If there are supposed to be two rooms, the racks are located in the center and on the sides.

The location of the rack depending on the length of the roof is shown in the figure.

Location of the rack depending on the length of the roof

Strut. Serves as a support for the rack.

Advice. Installing the brace at an angle of 45° significantly reduces the risk of deformation from wind and snow loads.

In regions with a significant wind and snow load, not only longitudinal struts are installed (located in the same plane with the rafter pair), but also diagonal ones.

Sill. Its purpose is to serve as a support for the rack and a place for attaching the strut.

crate. It is intended for movement during construction works and fixing of roofing material. It is installed perpendicular to the rafter legs.

Advice. An important purpose of the crate is to redistribute the load from the roofing material to the truss system.

The presence of a drawing and a diagram indicating the location of all the listed structural elements will help in the work.

Advice. Be sure to add data on the passage of the ventilation shaft and chimney to the scheme of the gable roof truss system.

The technology of their device is determined by the type of roof.

The choice of material for rafters

When calculating the material for a gable roof, you need to choose high-quality wood without damage and wormholes. The presence of knots for beams, Mauerlat and rafters is not allowed.

For boards, there should be a minimum of knots, and they should not fall out. Wood must be durable and treated with the necessary preparations that will enhance its properties.

Advice. The length of the knot should not exceed 1/3 of the thickness of the timber.

Calculation of the truss system of a gable roof

The calculation of material parameters is an important stage, so we present the calculation algorithm step by step.

Calculation of the rafter system It is important to know: the entire truss system consists of many triangles, as the most rigid element. In turn, if the slopes have a different shape, i.e. are an irregular rectangle, then you need to divide it into separate components and calculate the load and the amount of materials for each. After calculations, summarize the data.

1. Calculation of the load on the truss system

The load on the rafters can be of three types:

Permanent loads. Their action will always be felt by the truss system. Such loads include the weight of the roof, lathing, insulation, films, additional elements of the roof, finishing materials for the attic floor. The weight of the roof is the sum of the weight of all its constituent elements, it is easier to take into account such a load. On average, the value of the constant load on the rafters is 40-45 kg / sq.m.

Advice. To make the margin of safety for the rafter system, it is better to add 10% to the calculation.

For reference: The weight of some roofing materials per 1 sq.m. presented in the table

Advice. It is desirable that the weight of the roofing material per 1 sq.m. roof area, did not exceed 50 kg.

Variable loads. They operate at different times and with different strengths. Such loads include: wind load and its strength, snow load, precipitation intensity.

In fact, the roof slope is like a sail and, given the wind load, the entire roof structure can be destroyed.

Wind load on the roof

The calculation is carried out according to the formula: wind load is equal to the indicator for the region, multiplied by the correction factor. These indicators are contained in the SNiP "Loads and Impacts" and are determined not only by the region, but also by the location of the house. For example, a private house surrounded by high-rise buildings has fewer loads. A detached country house or cottage is experiencing increased wind loads.

2. Calculation of the snow load on the roof

The calculation of the roof for snow load is carried out according to the formula:

The total snow load is equal to the weight of the snow multiplied by the correction factor. The coefficient takes into account wind pressure and aerodynamic influence.

The weight of snow, which falls on 1 sq.m. roof area (according to SNiP 2.01.07-85) is in the range of 80-320 kg / sq.m.

The coefficients showing the dependence on the slope angle are shown in the photo.

The scheme for calculating the snow load on the roof

Nuance. With a slope angle of more than 60 ° snow load does not affect the calculation. Since the snow will quickly slide down and will not affect the strength of the timber.

Special loads. Accounting for such loads is carried out in places with high seismic activity, tornadoes, storm winds. For our latitudes, it is enough to make a safety margin.

Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).

Assessment of the condition and bearing capacity of walls and foundations

It should be borne in mind that the roof has a significant weight that can harm the rest of the building.

Determination of the roof configuration:

simple symmetrical;
simple asymmetric;
broken line.

The more complex the shape of the roof, the greater the number of roof trusses and truss elements is needed to create the necessary margin of safety.

3. Calculation of the angle of the roof

The angle of inclination of a gable roof is determined primarily by the roofing material. After all, each of them puts forward their own requirements.

soft roof - 5-20 °;
metal tile, slate, corrugated board, ondulin - 20-45 °.

It should be noted that increasing the angle increases the area of \u200b\u200bthe space under the roof, but also the amount of material. What affects the overall cost of work.

Calculation of the angle of the roof

Nuance. The minimum slope angle of a gable roof must be at least 5°.

5. Calculation of the pitch of the rafters

The pitch of the rafters of a gable roof for residential buildings can be from 60 to 100 cm. The choice depends on the roofing material and the weight of the roof structure. Then the number of rafter legs is calculated by dividing the length of the slope by the distance between the rafter pairs plus 1. The resulting number determines the number of legs per slope. For the second number, you need to multiply by 2.

6. Calculation of the length of the roof rafters

The length of the rafters for the attic roof is calculated using the Pythagorean theorem.

Parameter "a"(roof height) is set independently. Its value determines the possibility of arranging a dwelling under the roof, the convenience of being in the attic, the consumption of material for the construction of the roof.

Parameter "b" equal to half the width of the building.

Parameter "c" is the hypotenuse of the triangle.

Advice. To the value obtained, you need to add 60-70 cm for sawing and taking the rafter leg out of the wall.

It should be noted that the maximum length of the beam is 6 r.m. Therefore, if necessary, the timber for the rafters can be spliced (building, joining, joining).

The method of splicing the rafters along the length is shown in the photo.

Methods for splicing rafters along the length

The width of the rafters for the roof depends on the distance between opposite load-bearing walls.

7. Calculation of the section of the rafters

The cross section of the gable roof rafters depends on several factors:

load, we already wrote about it;

type of material used. For example, a log can withstand one load, a beam - another, a glued beam - a third;

rafter leg length;

type of wood used in construction;

distance between rafters (rafter pitch).

You can determine the cross section of the beam for the rafters, knowing the distance between the rafters and the length of the rafters, using the data below.

Rafter cross section - table

Advice. The larger the installation step of the rafters, the greater the load on one rafter pair. So, the cross section of the rafters needs to be increased.

Dimensions of lumber (beams and boards) for a gable truss system:

thickness (section) of the Mauerlat - 10x10 or 15x15 cm;

the thickness of the rafter leg and puffs is 10x15 or 10x20 cm. Sometimes a beam of 5x15 or 5x20 cm is used;

run and strut - 5x15 or 5x20. Depending on the width of the leg;

rack - 10x10 or 10x15;

lying down - 5x10 or 5x15 (depending on the width of the rack);

thickness (section) of the roof lathing - 2x10, 2.5x15 (depending on the roofing material).

Types of gable roof truss system

For the considered roof structure, there are 2 options: layered and hanging rafters.

Types of roof system: with layered and hanging rafters

Consider each type in detail in order to make an informed choice.

hanging rafters

They are used with a roof width of not more than 6 r.m. The installation of hanging rafters is carried out by attaching the legs to the load-bearing wall and the ridge run. The design of hanging rafters is special in that the rafter legs are under the influence of a bursting force. Hanging rafters with a puff installed between the legs can reduce its influence. The puff in the truss system can be wooden or metal. Often puffs are placed at the bottom, then they play the role of load-bearing beams. It is important to ensure that the puff is securely fastened to the rafter leg. Because a bursting force is also transmitted to it.

Advice.
The higher the puff is located, the greater the strength it should have.
If the puff is not installed, the load-bearing walls can simply “disperse” from the pressure created by the truss system.

Rafters

They are used in the arrangement of roofs of any size. The design of the layered rafters provides for the presence of a bed and a rack. Lying lying parallel to the Mauerlat takes on part of the load. Thus, the rafter legs seem to be inclined towards each other and are supported by the rack. The rafter legs of the layered system work only for bending. And the ease of installation also tips the scales in their favor. The only downside is the stand.

Combined

Due to the fact that modern roofs are distinguished by a large variety of shapes and complexity of configurations, a combined type of truss system is used.

Combined view of the truss system

After choosing the type of truss system, you can accurately calculate the amount of materials. Record the calculation results. At the same time, professionals recommend drawing up drawings for each element of the roof.

Installation of a gable roof truss system

After the gable roof rafters are calculated, installation can begin. We break the process into stages and give a description of each of them. You will get a kind of step-by-step instruction containing additional information on each stage.

1. Attaching the Mauerlat to the wall

The beam is installed along the length of the wall on which the rafters will rest.

In log cabins, the role of the Mauerlat is played by the upper crown. In buildings built from porous material (aerated concrete, foam concrete) or brick, the Mauerlat is installed along the entire length of the load-bearing wall. In other cases, it can be installed between the rafter legs.

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Splicing Mauerlat to each other (straight lock with bolts) Since the length of the Mauerlat exceeds the standard dimensions of lumber, it has to be spliced.

The connection of the Mauerlat with each other is done as shown in the figure.

How to connect the Mauerlat?

Washed down the bars is made only at an angle of 90 °. Connections are made using bolts. Nails, wire, wooden dowels are not used.

How to fix the Mauerlat?

The Mauerlat is installed on top of the wall. Mounting technology provides for several ways to mount the Mauerlat:

strictly in the center of the bearing wall;
offset to one side.

Advice.
Mauerlat cannot be placed closer than 5 cm to the outer edge of the wall.

To protect the beam for the Mauerlat from damage, it is laid on a layer of waterproofing material, which most often acts as an ordinary roofing material.

The reliability of fastening the Mauerlat is an important aspect of construction. This is due to the fact that the roof slope is like a sail. That is, it experiences a strong wind load. Therefore, the Mauerlat must be firmly fixed to the wall.

Methods for attaching the Mauerlat to the wall and rafters

Mauerlat fastenings with anchorsAnchor bolts. Ideal for monolithic construction.

Mauerlat fastenings with wooden dowelsWooden dowels. Are used for fellings from a log and a bar. But, they are always used with additional fasteners.

Mauerlat fastenings with brackets. Staples.

Mauerlat mounts on studs or fittingsStud or fittings. It is used if the cottage is built of porous materials (aerated concrete, foam concrete).

Mauerlat mounts with a sliding mountSliding mount (hinged). The bundle in this way allows you to ensure the displacement of the rafter legs when the house shrinks.

Mauerlat fastenings with wire Annealed wire (knitting, steel). It is used as an additional fastening in most cases.

2. Production of roof trusses or pairs

Installation is carried out in two ways:

installation of bars directly on the roof. It is not used often, since it is problematic to perform all the work, measurements, trimming at a height. But it allows you to completely do the installation yourself;

assembly on the ground. That is, individual elements (triangles or pairs) for the truss system can be assembled at the bottom, and then raised to the roof. The advantage of such a system is faster work at height. And the disadvantage is that the weight of the assembled roof truss structure can be significant. To lift it, you need special equipment.

Advice. Before assembling the rafter legs, you need to mark up. It is very convenient to use templates for this purpose. The truss pairs assembled according to the template will be exactly the same. To make a template, you need to take two boards, the length of each of which is equal to the length of one rafter, and are interconnected.

3. Installation of rafter legs

The collected pairs rise up and are installed on the Mauerlat. To do this, at the bottom of the rafter legs, you need to make a drink.

Advice. Since the slots on the Mauerlat will weaken it, you can only cut down on the rafter leg. To wash down was the same and fit snugly to the base, you need to use a template. It is cut out of plywood.

Methods for attaching the rafter leg are shown in the figure.

Methods for attaching the rafter leg

You need to start installing rafter pairs from opposite ends of the roof.

Advice. To properly install the rafter legs, it is better to use temporary struts and struts.

A twine is stretched between the rafter pairs. A twine is stretched between the fixed pairs. It will simplify the installation of subsequent rafter pairs. And also, will indicate the level of the skate.

If the rafter system is mounted directly on the roof of the house, then after installing the two extreme rafter legs, the ridge support is installed. Further, half of the rafter pairs are attached to it.

It is worth noting that the opinions of professionals differ on this issue. Some advise using a staggered mounting order, which will evenly distribute the increasing load on the walls and foundation more evenly. This order involves the installation of one rafter in a checkerboard pattern. After part of the rafter legs is installed, the missing parts of the pair are mounted. Others insist that you need to do a consistent installation of each pair. Depending on the size of the structure and the configuration of the truss, the reinforcement of the rafter legs is carried out with props and racks.

Fixing with rafter brackets Nuance. Additional structural elements are connected by cutting. It is preferable to fix them with building brackets.

If necessary, you can lengthen the rafter leg.

Methods for splicing rafter legs are shown in the photo.

Methods for splicing rafter legs

Advice. The method by which the Mauerlat is lengthened (washed down at 90 °) cannot be used in this case. This will weaken the rafter.

4. Installing the gable roof ridge

The ridge knot of the roof is made by connecting the rafter legs at the top.

Roof ridge device:

Method without using a support bar (see fig.).

Installation of the roof ridge without the use of a support beam

A method using a rafter bar. Timber is needed for large roofs. In the future, it can become a support for the rack.

The method of laying on the beam.

Installing the roof ridge by laying on the timber
Installing the roof ridge by laying on the timber

A more modern version of the manufacture of the ridge knot can be considered the method shown in the photo.

Method for making a ridge knot

Cutting method.

Installation of the roof ridge by cutting

After the truss system is installed, we make a major fixing of all structural elements.

5. Mounting the roof sheathing

The crate is mounted in any case, and is designed for more convenient movement along the roof during work, as well as for fixing roofing material.

The step of the lathing depends on the type of roofing material, for example:

under the metal tile - 350 mm (the distance between the two lower boards of the crate should be 300 mm).
under corrugated board and slate - 440 mm.
under the soft roof we lay a continuous crate.

Rafter system of a gable roof with an attic - video:

Conclusion

As you can see, despite the seeming simplicity, the installation of a gable roof truss system contains many pitfalls. But, based on the above recommendations, you can easily build a reliable structure with your own hands.

Tags: Roof Gable roof Rafter

21.02.2017 1 Comment

The truss system of a gable roof is a simple design that is available for a do-it-yourself device even for a novice developer. It is only necessary to make preliminary calculations, familiarize yourself with the details and stages of the construction of the roof, and calculate the materials needed for installation. When calculating, it should be taken into account that the bearing capacity of a gable roof depends on the influence of loads from wind, snow, and the weight of materials on it.

In order to make the process of building a gable roof truss system as easy as possible for you, below is a detailed step-by-step instruction for installing a truss system with your own hands.

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Requirements for building materials

For the installation of a truss system, the best option would be to use sawn timber from coniferous wood - pine, spruce or larch, grades I - III.

The material for the rafters is taken not lower than grade II, the mauerlat is made from boards or timber of grade II, for racks and girders material of grade II is taken, the crate is made of grade II-III lumber, it depends on the roof. Crossbars, puffs are made of Grade I material. On linings, linings, material of grade III can be used.

Note! Lumber must be dry with a moisture content of not more than 20%. Before installation, it should be treated with flame retardants and antiseptics against fungal diseases.

You need to store lumber under a canopy, providing protection from the sun and moisture. Level the storage area, shift the lumber with linings for ventilation.

For installation, fasteners are required: ties, plates, studs, bolts with washers and nuts, self-tapping screws with EPDM gaskets, 2.8 mm thick, mounting tape, galvanized brackets.

Brackets are used when fastening the Mauerlat, they are fastened with nails or self-tapping screws.

KR corners serve to attach the rafters to the Mauerlat, prevent the rafters from moving.

All fixing material must be made of high quality material and protected against corrosion.

Tools for the construction of the truss system

To install the gable roof truss system, you will need the following set of tools:

tape measure, different lengths 5, 10, 20 meters;
markers, pencils;
cord, for stretching;
hammers, various purposes, nail puller;
scissors, for cutting;
roofing knife;
putty knife;
scotch;
hacksaws, electric saw, electric drill with various drills and nozzles;
screwdriver with nozzles;
markings, horizontal and vertical levels;
rails, rulers;
mounting foam;
safety belt and rope - for safe work.

Keep all roofing tools in a tool bag for safety.

Types of truss systems for a gable roof

sent rafters

They rely on the Mauerlat and racks installed on the inner wall, with a step equal to the rafters. To give rigidity during spans of 6 m, struts are additionally placed.

The scheme of the rafters of a gable roof

hanging rafters

If the building is of a small width, it is possible to arrange a truss system when the rafters rest on the mauerlat or walls, without intermediate supports. The maximum span is 9 meters. Such roofs can sometimes be arranged without a Mauerlat. The rafters are installed on the wall, using gaskets, on the rafters in this embodiment, a bending moment acts.

To unload, put wooden or metal lining. They securely reinforce the corner. For hanging rafters of a larger span, a headstock and struts are installed. For hanging systems, the rafters are arranged with a larger section, and the lumber is chosen not lower than grade I II.

Scheme of hanging rafters of a gable roof

Calculation of the truss system

It is possible to determine the cross-section of a gable roof beam required in the truss system by collecting all the loads acting on it: the weight of the coating, lathing, snow, wind pressure, precipitation.

Permanent loads can be determined by the weight of 1 m 2 of roofing, battens. It is important that the weight per 1 m 2 of the roof is in the range of 40-45 kg.

Variable loads from snow, wind are calculated according to the tabular values of SNiP normative documents, depending on the height of the building, temperature zone. The load from snow is equal to its weight multiplied by a coefficient depending on the slope of the slope. All these calculations are carried out during the project.

And if there is no project, and the roof is being erected on a small building? You need to look at the construction of a house in the neighborhood, which is carried out according to the project, the roof area is the same as your building. The gable roof truss system will serve as a model.

Rafter beam dimensions

At the top point, a ridge is laid that connects the rafters. The height of the ridge depends on the slope of the roof. The slope is influenced by the choice of coating material. The minimum dimensions are:

for tiled roofs, slate 22 gr.;
for metal tiles - 14 gr.;
ondulin - 6 gr.;
corrugated board - 12 gr.

The optimal angle is 35-45 gr. slope, provides a quick discharge of water and snow. In regions with strong winds, the roofs are made flat and then the angle of inclination is within 20-45 degrees.

You can determine the height by the formula: H \u003d 1 / 2 Lpr * tgA. Where A is the angle of inclination, L is the width of the building.

The task is simplified when using a ready-made table. The coefficient depends on the width of the building and the angle of inclination. Multiply the coefficient by 1⁄2 of the width of the building.

The rafters are made from pine or spruce bars, with a section of 50 × 100 mm, 50 * 150 mm.

The size of the rafters depends on the pitch. The pitch of the rafters is smaller, a larger number is installed, the cross section will decrease. The distance between the rafters at a gable roof is in the range from 600 mm to 1800 mm, it all depends on the design of the roof and the materials used for its construction.

Table of rafter sizes, depending on the step of their installation

Length rafters, mm	Distance between rafters, mm	Rafter beam section size, mm
up to 3000	1200	80×100
up to 3000	1800	90×100
up to 4000	1000	80×160
up to 4000	1400	80×180
up to 4000	1800	90×180
up to 6000	1000	80×200
up to 6000	1400	100×200

The roof does not end at the level of the walls, it is extended 500 mm outwards. The rafter leg can protrude, or a board or bar is built up. In this case, moisture does not fall on the wall, the foundation is not poured.

Step-by-step installation of the design of the gable roof truss system

The gable roof truss system consists of the following elements:

Mauerlat.
Lie down.
Racks.
Rafter.
Struts.
Puffs.
Crate.

Mauerlat installation

Mauerlat fasteners to a monolithic reinforced concrete belt

Mauerlat evenly distributes the load on the walls of the building, its installation can be done in several ways:

fasten to the wall through a reinforced concrete belt with studs;
studs are inserted into the masonry;
a simple and common way for simple roofs, fastening with wire rod.

For him, take a bar with a section of 100 × 100 mm, 150 × 150 mm or 200 × 200 mm. Which section to choose depends on the size of the roof and its coverage. The Mauerlat is joined along the length, for this, make a 100 mm cut, 500 mm long, fold the bars and fasten with studs.

In the corners, the Mauerlat is tied with cuts to the floor of the beam, fastened with brackets or bolts. For wooden buildings, Mauerlat is the last crown. On brick walls, make a monolithic reinforced reinforced concrete belt, with a section of 400 × 300 mm. Align the pins with a thread of 12 mm in diameter along the belt, through 120 mm, for fastening.

Drill holes with a diameter of 12 mm in the Mauerlat, lay them so that the pins go into the holes. Tighten with nuts from above. Previously, we lay two layers of roofing material or roofing felt under the bar. On the outside of the wall, lay the Mauerlat with bricks. Laying the Mauerlat on a horizontally and vertically even base. It is necessary to check the horizontal level of the surface. Check diagonals. Align with pads if necessary.

Installation instructions for beds, racks, rafters, struts and puffs

Do-it-yourself do-it-yourself installation of a gable roof truss system is carried out in the following order:

To carry out the installation of the bed, with the sent rafters.
Mark the installation step of the rafter legs.
Prepare according to the size of the rack.
Install them, if necessary, unfasten them with spacers.
Lay a run. Check geometry. Install fastener.
Try on the first rafter leg, mark the cutting points.
Mark the points and install the rafters at the beginning and end of the roof, pull a cord between them in order to align the rest of the elements with it.
Having installed the rafter leg, we attach it first to the Mauerlat, then to the ridge run, to each other.
Screw every second leg with wire to the Mauerlat.

The fastening of the rafters to the Mauerlat is done with the help of notches, thrust corners and a hemmed support bar. Reinforce with nails or staples.

Methods for attaching rafters to the Mauerlat

Install the support posts on the beds or linings and linings. A bed is a beam 50 × 100 mm or 50 × 150 mm, laid on the middle wall along a roofing felt lining. Place brick columns under the lining, 2 bricks high.

The rafter legs are connected to each other on the ridge. Consider the common connection nodes of the truss system:

They make cuts at one leg and washed down at the other. Insert one leg into the cut of the other and fasten with a bolt.
Install overlays, wooden or metal.
With the help of cuts in the run, they are fixed with nails or bolts.

Methods for connecting rafters on a ridge

For the stability of the roof to wind loads, puffs, struts and runs are installed. The tightening is a bar 100 × 150 mm, runs and struts are made from a bar 50 × 150 mm or 100 × 150 mm.

With the installation of contractions, the reliability of the rafter design increases. The sections of the beam are the same as the rafters. They are attached to the legs with bolts or nails. The bracing device adds rigidity to the structure. They are installed tightly, to the surface of the rafters.

Lumber has a standard length of 6 m. Rafters can be longer. Then you need to connect them. There are several connection methods:

Fasten by applying bars on both sides at the junction, connect them with nails in a checkerboard pattern.
Overlap, one part of the rafter to another, at a distance of 1 meter, fasten with nails in a variable order.
Run a cut obliquely, cut out part of the legs of the rafters, connect them, reinforcing them with bolts.

Lathing device

A crate is laid along the roof rafters. It serves to distribute the load from the roofing material, snow on the rafters. It plays the role of an air gap between the roof and the truss system.

The design of the crate depends on the accepted roofing material:

under the soft tiles, make the crate continuous, an anti-condensate film is laid on the rafters, it is pressed on top with a counter rail, the crate is nailed onto it, then the OSB boards and the lining carpet, we lay the tiles on top.
under the roof of the corrugated board, the crate should be sparse. The step of the lathing depends on the brand of corrugated board, its thickness and the angle of the roof.
make a crate for standard slate in increments of 500 mm from a bar 75 × 75 mm or 50 × 50, as well as boards from 30 × 100 mm. It is necessary to take into account the design features of the roof, with the final choice of a suitable option.

The lumber from which the crate is made is pine of the first or second grade. It is advisable to take a width of no more than 14 cm. With a width of more, the boards can warp and damage the roofing. The length of the nails should be three times the thickness of the crate. Lay boards along the ridge. Set the first board of greater thickness to the height of the roofing.

To arrange a continuous crate along the slope of the roof.

With the first layer, lay a board along the ridge from it at a distance of 500-1000 mm next, and so on. With the second layer, lay the crate in the direction along the rafters. Arrange the joint between the boards only on the rafters in a run. The nail is sunk completely with the head into the pulp of the wood.

Cornice overhangs

Arranged to protect against precipitation, play an aesthetic role. Eaves overhangs suit tightly without gaps. The final stage in the construction of the roof.

Scheme of the device of the eaves overhang of a gable roof

Gable

The gable roof has two gables. They have the shape of a triangle, with the apex at the ridge and the sides coincide with the slopes of the roof. Gables support the rafters and enclose the attic space. Protect from wind and precipitation, give stability to the roof.

In wooden buildings, the pediment is made frame. In brick buildings, frame or brick. Gables made of brick or gas block are erected before the roofing device. They require very precise execution.

Frame gables fit into the finished opening when the truss system is already assembled.

The frame is made of bars or boards. The frame elements are connected on spikes or to the floor of a tree, all fastened with nails. They are sheathed by nailing boards, lining or siding, maintaining the color in the decoration of the facade of the building. For the device of a window opening, an additional frame is made under it according to the size of the window. If the attic is insulated, then the pediment also needs to be insulated. Insulation is laid in the middle of the frame. A mineral wool insulation with reduced flammability is used. From the outside, the frame is upholstered with a hydro-windproof film or a windproof membrane, from the inside, a vapor-tight film or a vapor-tight membrane is nailed under the finishing material.

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The arrangement of a gable roof is considered a very practical and right decision in the construction of a residential or commercial building. This option combines the relative simplicity of execution and reliability, ease of maintenance and long service life. In this material, we will talk about how to install a gable roof truss system with your own hands, what are its varieties, and how to calculate the dimensions of its individual elements. Our step-by-step instructions will allow you to deal with any complications that may arise in the process.

A roof with two slopes has a whole list of advantages:

ease of calculation;
various versions;
saving materials;
the possibility of natural outflow of water;
low probability of water leakage due to the integrity of the structure;
the possibility of arranging an attic or attic;
reliability and long service life;
ease of preventive maintenance.

Varieties of gable roofs

Consider the main types of roofs with two slopes, the truss system in which will differ slightly in execution.

Symmetrical gable roof

This is the simplest gable roof, however, the most reliable and in demand. Symmetrical slopes allow you to distribute the load on the Mauerlat and load-bearing walls evenly. In this case, the type and thickness of the insulation layer do not affect the choice of roofing material. Thick beams of rafters have a sufficient margin of safety, so they will not sag. In addition, spacers can be installed at your discretion.

Among the disadvantages of this option, one can only note a too sharp angle of the slopes, which makes it difficult to use the attic floor and creates “deaf” zones that have no use.

Roof with two asymmetrical slopes

If the angle of inclination of the slopes is made more than 45º, some unused areas of space can be used. It will even be possible to equip a living space in the attic. However, some additional calculations will be required, as the load on the walls will become uneven.

Broken roof with external or internal break

This configuration makes it possible to place a spacious attic or attic under the roof. However, in this case, more complex engineering calculations will be required.

The design of rafters for arranging a roof with two slopes

The design of the gable roof truss system assumes the presence of such components:

Mauerlat. It is a durable bar made of oak, pine, larch or other strong wood species, which is laid around the perimeter on the load-bearing walls of the building. The purpose of the Mauerlat is to evenly distribute the load. The cross section of the bars is chosen based on their structure - solid or glued, as well as on the age of the building. The most commonly used beams are 100 × 100 or 150 × 150 mm.
rafters. The whole structure is created from such elements (read also: ""). Connecting at the top point, two rafters form a farm. They are made from logs or durable bars.
puff. This part serves to grip the rafters and ensure their rigidity.
Runs. In those places where the rafter legs are joined, a ridge run is attached, on which the skate will subsequently be mounted. And with the help of side runs, the frame of the rafters is given additional strength. The expected load determines the size and number of such elements.
Rafter rack. This is a vertical beam that partially takes over the weight of the roof. If the gable roof scheme is simple, then one such beam is placed in the center. For a long span, three bars may be required - one in the center and two on the sides. If an asymmetrical roof is being erected, then the location of such a beam is determined by the length of the rafter legs. Under the rafters for a sloping roof, racks are placed on the sides to make room for movement. Beams are placed in the center and sides if there are two rooms.
Struts. These are rack supports. If significant winds and precipitation are expected in the winter, longitudinal as well as diagonal racks are installed.
Sill. A rack for rafters rests on it, and struts are also attached.

crate. The selected roofing material is attached to it, and you can also move along it during work. Fix the crate perpendicular to the rafters. Please note that the crate allows you to evenly distribute the mass of roofing material over the rafter system.

The installation scheme of the gable roof truss system will greatly facilitate all construction work. How such a roof scheme will look depends on the type of roof.

Please note that the material for the truss system must be of the highest quality, treated with flame retardant and antiseptic agents. There should be no knots or cracks on the beams for rafters, Mauerlat and racks. Only a small number of knots are allowed on the crate, firmly seated in the wood.

Calculation of frame elements for a gable roof

Laying Mauerlat on the walls

This element is mounted on a load-bearing wall along its entire length. If we are talking about a log house, then the upper crown can serve as a Mauerlat. For buildings made of aerated concrete or brick, a Mauerlat equal to the length of the wall will be required. Sometimes this detail can be laid between the rafters.

With a lack of material length for the Mauerlat, several pieces can be spliced. At the same time, the edges are sawn at 90º and joined with bolts - wire, dowels or nails are not suitable.

There are two ways to lay a Mauerlat on top of a load-bearing wall:

symmetrically in the center;
offset in the desired direction.

Mounting of the Mauerlat is carried out on a pre-laid waterproofing layer of roofing material. This will protect the wood from rotting.

It is worth taking a responsible attitude to the process of attaching the Mauerlat, since in strong winds it must withstand a particularly heavy load.

As fasteners for Mauerlat, you can use the following consumables:

Anchors, which are indispensable for monolithic materials.
Wooden dowels. These parts are used in houses made of timber and logs, although they require additional fastenings.
Staples.
Reinforcement or special studs. This option is preferable for buildings made of foam or aerated concrete.
Knitting or steel wire is an auxiliary fastener that is used almost always.

Assembly of trusses or trusses

Farm assembly can be done using one of the following methods:

Beams for rafters are assembled and mounted directly on the roof of the building. This process is quite laborious, since all measurements, trimming and coupling of the bars will have to be done at a height. However, you can do it on your own, without the involvement of technology.
Trusses or truss pairs can be fixed to the ground, and then the finished elements can be raised to the roof of the building. On the one hand, this simplifies the process of installing the rafters, and on the other hand, due to the large weight of the structure, lifting it up will require special equipment.

Please note that it is worth starting the assembly of truss pairs only after marking. And if you make a template in advance, for which you take two boards equal to the length of the rafters, and connect them together, then all pairs will turn out to be exactly the same.

Installation of rafters

After assembly and lifting to a height, the rafters of the gable roof of a wooden house are installed. To fix them on the Mauerlat, cuts are made at the bottom of the rafters. The first to install two trusses from opposite ends of the roof.

After that, a rope is pulled between the starting pairs, along which all the other truss trusses will be aligned and the ridge will be installed.

Now you can mount the remaining pairs in compliance with the calculated step between them. In cases where pairs are assembled directly on the roof, a ridge run is attached between the two end trusses. Subsequently, rafters are installed on it.

The order of installation of halves of rafters according to the opinions of professionals may differ. Some prefer to lay the bars in a checkerboard pattern so as not to overload the foundation and walls during work. Others tend to install pairs of rafters in series. Be that as it may, rafter legs may need props and racks - it all depends on the size of the roof and the shape of the trusses.

Skate mount

A ridge is an element that is formed by attaching rafters at the top point. As soon as all the details of the truss system for a gable roof are installed, it is necessary to perform a major fixing of all structural elements.

Lathing installation

The presence of lathing is mandatory in the construction of any roof. It not only supports the roofing material and allows it to be securely fastened, but also makes it possible to move along the roof during work.

The distance between the individual boards is chosen based on the type of roofing material:

soft roofing is laid on a continuous crate without gaps;
for a metal tile, a crate is needed with a step of 35 cm (between the two lower rows - 30 cm);
slate and corrugated board can be laid on the crate in increments of 44 cm.

Results

Thus, in order to assemble a truss system for a roof with two slopes, many nuances should be taken into account and any possible complications should be foreseen. We hope that our advice will help you cope with this difficult task and create a high-quality and durable roof for your home.

In order for such a valuable part of the roof to flawlessly cope with the listed tasks, information about the rules and principles of its construction is needed. The information is useful both for those who are constructing the gable roof truss system with their own hands, and for those who decide to resort to the services of a hired team of builders.

In the device of the truss frame for pitched roofs, wooden and metal beams are used. The starting material for the first option is a board, log, timber.

The second is constructed from rolled metal: a channel, a profile pipe, an I-beam, a corner. There are combined structures with steel most loaded parts and wood elements in less critical areas.

Rafters - a fundamental element

The rafters used in the construction of the gable roof frame are divided into:

Layered rafter legs, both heels of which have reliable structural supports under them. The lower edge of the layered rafter rests on the Mauerlat or on the ceiling crown of the log house. The support for the upper edge can be a mirror analogue of the adjacent rafter or a run, which is a beam horizontally laid under the ridge. In the first case, the truss system is called spacer, in the second, non-spacer.
hanging rafters, the top of which rests against each other, and the bottom is based on an additional beam - puff. The latter connects the two lower heels of adjacent rafter legs, resulting in a triangular module called a truss truss. The tightening dampens the tensile processes, so that only a vertically directed load acts on the walls. The design with hanging rafters, although it is spacer, does not transfer the spacer to the walls.

For the arrangement of supports for the top of the layered rafters, beds and girders are mounted. In reality, the truss structure is much more complicated than the elementary patterns described.

However, we are now specifically interested in the device of the gable roof truss system, and it can involve either hanging or layered rafters, or a combination of both types.

Subtleties of fastening rafter legs

The rafter system is fastened to brick, foam concrete, aerated concrete walls through the mauerlat, which in turn is fixed with anchors.

Between the Mauerlat, which is a wooden frame, and the walls of these materials, a waterproofing layer of roofing material, waterproofing, etc. is necessarily laid.

How to do without furious calculations?

However, even if the step required for the correct installation of the roof is exceeded, there is a way out. This is a reinforcing counter-lattice device. True, it will increase both the weight of the roof and the construction budget. Therefore, it is better to deal with the step of the rafters before the construction of the rafter system.

On our website you can find, which may also help you a lot during construction.

Rafter structures of layered type

Distinctive design features:

Mandatory presence of support under the ridge heel of the rafter leg. The role of the support can be played by a run - a wooden beam resting on racks or on the inner wall of the building, or the upper end of an adjacent rafter.
The use of Mauerlat for the construction of a truss structure on walls made of brick or artificial stone.
The use of additional runs and racks where the rafter legs, due to the large size of the roof, require additional support points.

The minus of the scheme is the presence of structural elements that affect the layout of the internal space of the operated attic.

If the attic is cold and the organization of useful premises is not supposed to be in it, then the layered construction of the truss system for the installation of a gable roof should be preferred.

A typical sequence of work on the construction of a layered truss structure:

First of all, we measure the height of the building, the diagonals and the horizontalness of the upper cut of the skeleton. When identifying vertical deviations of brick and concrete walls, we eliminate them with a cement-sand screed. Exceeding the heights of the log house we squeeze. By placing chips under the Mauerlat, vertical flaws can be dealt with if their magnitude is insignificant.
The floor surface for laying the bed must also be leveled. He, the Mauerlat and the run must be clearly horizontal, but the location of the listed elements in the same plane is not necessary.
We process all wooden parts of the structure before installation with fire retardants and antiseptic preparations.
We lay waterproofing on concrete and brick walls for the installation of a Mauerlat.
We lay the Mauerlat beam on the walls, measure its diagonals. If necessary, we slightly move the bars and turn the corners, trying to achieve the perfect geometry. Align the frame horizontally if necessary.
We mount the Mauerlat frame. The splicing of the beams into a single frame is carried out by means of oblique cuts, the joints are duplicated with bolts.
We fix the position of the Mauerlat. Fasteners are made either with brackets to wooden plugs laid in the wall ahead of time, or with anchor bolts.
We mark the position of the bed. Its axis should recede from the Mauerlat bars at equal distances on each side. If the run will be based only on racks without lying down, the marking procedure is carried out only for these columns.
We install the bed on a two-layer waterproofing. We fasten it to the base with anchor bolts, connect it to the inner wall with wire twists or staples.
We mark the installation points of the rafter legs.
We cut out racks according to uniform sizes, because our bed is set to the horizon. The height of the racks must take into account the dimensions of the section of the run and the bed.
Installing racks. If provided by the project, we fix them with spacers.
We lay the run on the racks. We check the geometry again, then install the brackets, metal plates, wooden mounting plates.
We install a trial rafter board, mark the places of trimming on it. If the Mauerlat is set strictly to the horizon, there is no need to adjust the roof rafters in fact. The first board can be used as a template for making the rest.
We mark the installation points of the rafters. Folk craftsmen for marking usually prepare a pair of slats, the length of which is equal to the gap between the rafters.
According to the markup, we install the rafter legs and fasten them first at the bottom to the Mauerlat, then at the top to the run to each other. Every second rafter is screwed to the Mauerlat with a wire bundle. In wooden houses, the rafters are screwed to the second crown from the top row.

If the rafter system is done flawlessly, the layered boards are mounted in random order.

If there is no confidence in the ideal structure, then the extreme pairs of rafters are installed first. A control twine or fishing line is stretched between them, according to which the position of the newly installed rafters is adjusted.

Another useful video about the construction of a gable truss base with your own hands:

Hanging truss systems

The hanging type of truss systems is a triangle. The two upper sides of the triangle are folded by a pair of rafters, and the puff connecting the lower heels serves as the base.

The use of tightening allows you to neutralize the effect of the spread, therefore, only the weight of the crate, the roof, plus, depending on the season, the weight of precipitation, acts on walls with hanging truss structures.

The specifics of hanging truss systems

Characteristic features of hanging type truss structures:

Mandatory presence of a puff, made most often of wood, less often of metal.
The ability to refuse the use of Mauerlat. A frame made of timber will be successfully replaced by a board laid on a two-layer waterproofing.
Installation on the walls of ready-made closed triangles - roof trusses.

The advantages of the hanging scheme include the space under the roof free from racks, which allows you to organize an attic without pillars and partitions. There are disadvantages.

The first of these is the limitation on the steepness of the slopes: their slope angle can be at least 1/6 of the span of a triangular truss, steeper roofs are strongly recommended. The second disadvantage is the need for thorough calculations for the competent device of cornice nodes.

Subtleties of long-span hanging systems

Puff - the longest element of the hanging rafter structure. Over time, it, as is typical of all lumber, deforms and sags under the influence of its own weight.

Owners of houses with spans of 3-5m are not too concerned about this circumstance, but owners of buildings with spans of 6 meters or more should think about installing additional parts that exclude geometric changes in tightening.

To prevent sagging in the installation scheme of the truss system for a large-span gable roof, there is a very significant component. This is a pendant called a grandmother.

Most often, it is a bar attached with wooden surfs to the top of the truss truss. You should not confuse the headstock with the racks, because. its lower part should not come into contact with the puff at all. And the installation of racks as supports in hanging systems is not used.

As a result, the truss system pleases with stability with a slight and not too expensive upgrade.

Hanging type for attics

It is attached to the rafters by cutting with a semi-frying pan with a duplication of a bolt. It is protected from sagging by installing a short headstock.

A noticeable drawback of the attic hanging structure is the need for accurate calculations. It is too difficult to calculate it on your own, it is better to use a ready-made project.

Which design is more cost effective?

Cost is an important argument for an independent builder. Naturally, the price of construction for both types of truss systems cannot be the same, because:

In the construction of a layered structure for the manufacture of rafter legs, a board or beam of small section is used. Because layered rafters have two reliable supports under them, the requirements for their power are lower than in the hanging version.
In the construction of a hanging structure, the rafters are made of thick timber. For the manufacture of puffs, a material similar in cross section is required. Even taking into account the rejection of the Mauerlat, the consumption will be significantly higher.

Saving on the grade of material will not work. For the bearing elements of both systems: rafters, purlins, beds, Mauerlat, attendants, racks, lumber of the 2nd grade is needed.

For crossbars and puffs working in tension, you will need the 1st grade. In the manufacture of less responsible wooden slips, the 3rd grade can be used. Without counting, we can say that in the construction of hanging systems, expensive material is used to a greater extent.

Video instruction on the installation of a truss structure of a hanging category:

There are actually many more methods for constructing truss systems for roofs with two slopes.

We have described only the basic varieties that are actually applicable for small country houses and buildings without architectural ideas. However, the information provided is sufficient to cope with the construction of a simple truss structure.