The roof of the building protects it from the cold, rain and wind. It is as important an element as the exterior walls and foundation. The truss system is the supporting frame of the roof. It takes on all the loads: from structures, from snow and wind. In order to avoid problems during operation, the roof structure of the house must be strong and reliable. Do-it-yourself installation of the truss system should be performed only after careful preparation and study of all the necessary information.
Roof and roof
Before you start building the roof of a private house, you need to distinguish between two concepts. Non-professionals are often confused, but builders clearly separate the definitions of roof and roofing. The roof is the entire structure that separates the building from the street above. The roof structure of a private house includes rafters, all other load-bearing elements, thermal insulation material, roofing.
Rafters - load-bearing roof structures
The roof is top part roofs. It is also roofing.. Roofing requires careful selection of material. After all, the reliability of waterproofing and comfort of living will depend on it.
System Requirements
To properly mount the truss system with your own hands, you must take into account a certain set of rules. Without taking them into account, the structure will not be able to effectively resist negative influences from outside.
The first thing to consider is strength. All elements must withstand the load without destruction. The device of the roof truss system involves a preliminary calculation of the supporting structures for the first limit state. It is he who checks the elements of the truss system for strength.
The truss system must be strong and rigid The second requirement is rigidity. The maximum deflection is taken into account here. The roof structure of a wooden house or any other should not sag too much. Permissible deformations in the middle of the span are equal to the length of this span divided by 200. Before starting construction, the design of the truss system must be calculated according to the second group of limit states - for rigidity.
Do-it-yourself roof rafters are made taking into account that the structure is light in weight. Otherwise, the load on the walls and foundations increases greatly. It is for this reason that wood has become widespread as the main material. The wooden truss system has sufficient strength, but weighs relatively little. Attention should be paid not only to the design of the roof, but also to correctly choose the roofing material. It shouldn't be too heavy. Ceramic tiles lost its popularity not only because of the cost, but also because the roof of the house, its walls and foundations should be strengthened under it.
The weight roofing material for wooden roof structure shouldn't be too big Special requirements are placed on the quality of the material. Manufacturing wooden elements should be made only from good raw materials. It is worth considering the following recommendations:
- For the main elements, wood of 1 or 2 grades is used. Grade 3 can only be used for battens and other small parts.
- truss structures pitched roofs recommended to be made from coniferous species. They are more resistant to decay and other troubles because they contain resin. With the same cross section, the allowable span for hardwood will be less.
- Before starting work, all elements must be treated with an antiseptic. This stage of preparation allows you to prevent many troubles in the future. Also, if desired, you can treat the tree with flame retardants. This will increase fire resistance.
- It is better to buy wood from northern regions, which is prepared in winter period. This material is of the highest quality.
Construction parts
The scheme of the truss system includes many elements. To understand the drawings and correctly perceive the information, you need to know at least the basic ones. So what is the roof made of?
Ridge, cornice and slopes - the main part of the roof First of all, it is a ridge, a cornice and slopes. These elements are the main parts. The ridge is the topmost part of the structure. Cornice or overhang - lower. Slopes are inclined surfaces that are located between the ridge and the eaves.
The construction of the truss system requires knowledge of the load-bearing elements. These include:
- Mauerlat - timber, which is laid along the edge of the walls of the building. Mauerlat is needed to evenly transfer the load from rafter legs, which are based pointwise. Usually, for its manufacture, a bar with dimensions of 150x150 mm or 200x200 mm (for large buildings) is used.
- Rafter legs are inclined beams that transfer the load from the own weight of the roof, snow and wind to the Mauerlat. Such beams are usually installed from the ridge to the eaves. But when erecting a hip roof, elements appear that have only one of the specified points. They are supported on a ridge or on a cornice. Such details are called spawns. They usually have the same section as the rafters. In fact, sprigs are rafter legs cut off on one side.
- Run - a beam on which the elements of the roof rest. The run can be installed under the racks. Another option - ridge run(crossbar). The rafters rest on it at the highest point. The cross section of the run depends on its span, usually 200x200 mm is taken.
- Slanting legs are needed only for hip roofs. They represent diagonal rafters leaning on the Mauerlat at the corners. The cross section is taken enlarged, usually 150x200 or 100x200 mm.
- Design wooden roof assumes the presence of puffs, struts and racks. They are designed to reduce the load on the main elements. When building a house with your own hands, it is important to remember that the racks cannot be supported on the floor span. Installation is possible only on the underlying walls or on runs thrown between the walls. It is possible to mount such elements on the ceiling only if it is designed for such a load and reinforced in the desired area.
- The crate is needed in order to make the base under the coating. For metal tiles and seam roofing, the lathing can be sparse from boards with a thickness of 32-40 mm. For bituminous tiles, you need a solid base of boards 25-32 mm thick or moisture-resistant plywood.
- In order to make a departure of the cornice, filly is installed. They become a continuation of the rafters. The filly is attached to the rafter for a length of at least 1 m. The section of the element is usually taken as 50x100 mm.
load-bearing elements hip roof Another element of the truss system is the truss. This is a one-piece structure, which consists of rafters, puffs, struts and racks, rigidly interconnected. The truss has a triangular shape, and inside it is divided into several smaller triangles, which provides it with good stability.
Roof shapes
Roofs of pitched roofs are different forms. It is worth highlighting here:
Types of rafters
There are two designs:
- with layered rafters;
- with hanging rafters.
The device of the roof of a wooden house is possible only with the use of the first. This is due to two rules:
- hanging rafters must be rigidly attached to the Mauerlat;
- in a wooden house, the rafters must be hinged to the Mauerlat.
These two statements contradict each other, so the truss system of a wooden house can contain only layered elements.
In a wooden house, only layered rafters are mounted Layered beams are elements that rely on the Mauerlat at the bottom point and on the ridge run at the top.. This allows you to reduce the horizontal thrust that acts on the walls when the rafters try to part and take a horizontal position. Elements can be reinforced with struts or struts. Contractions in this case can be placed through one pair of legs.
Hanging tanks rest only at the lowest point on the Mauerlat. Above, they simply rest against each other. So that the system of wooden elements does not part, be sure to make puffs. It is better to install them on each pair of legs. This option is characterized by a strong thrust effect on the outer walls, but it allows you to get more free space inside the attic.
Connections
Before you make a rafter system with your own hands, you need to carefully study the nodes. To build your house, it is not worth saving time or money. Only in this case the result will please long years.
The main nodes of the connection of the rafters The attachment points of the roof truss system, which deserve special attention, are as follows:
- fastening the Mauerlat to the wall;
- fastening rafters to the Mauerlat;
- fastening the rafters at the top point;
- splicing rafters along the length.
Mauerlat to the wall
This knot can be done in several ways. The choice largely depends on the material of the wall. The construction of a building from brick, blocks or concrete allows the use of the following methods:
- on the wire;
- on staples;
- on studs;
- on the anchor with the device of a monolithic belt along the edge of the wall.
The connection of the Mauerlat with the wall during the construction of brick buildings is carried out using anchors Rafter to Mauerlat
Fasteners are carried out in two ways:
- tough for buildings made of brick, concrete or concrete blocks;
- articulated for wooden houses.
Rigid fastening can be with or without a notch. The cut is recommended to be done on the rafters, and not on the Mauerlat, as this weakens it. In both cases, the leg is rigidly fixed with nails, screws, staples or metal corners.
With rigid fastening, it is better to make a cut on the rafters and fix the structure with fasteners For hinged fastening, a special part is used - a sled. They allow the beam to move without obstacles when the walls of the building shrink.
Articulation allows the beam to move Additionally, rafter legs are attached to the wall. This is necessary so that the roof is not blown off by the wind. For fastening, a twist of two wires with a diameter of 4 mm is used, fixed to the wall on an anchor or ruff. In a wooden house, twisting can be replaced with staples. Fastening is carried out on each beam or through one.
At the skate level
Layered elements rest on a ridge run with a notch. Additionally, on both sides they make an overlay from the board. An overlay is also needed for hanging elements. It can be wooden or metal with holes for self-tapping screws.
The ridge run and rafters are connected using a cut Rafter splicing
There are several methods for splicing roof rafters with your own hands. The choice between them largely depends on the experience of the master. The splicing point is located at a distance of 0.15 of the span from the support. At the same time, not only the ridge run and the Mauerlat are considered supports, but also the struts and racks.
Splicing rafters along the length There are five ways:
- butt joint;
- oblique cut;
- overlap;
- compound legs;
- paired legs.
To build quality roof, you need to carefully study the technology, choose the right type of rafters and ways to connect elements in important nodes. This is especially important when building a truss system with your own hands.
They say that the roof of the house is the fifth facade. Any owner of a country cottage knows well that the overall perception of the structure depends on how well the roofing is chosen.
We have already told users of our site about the features of the choice of roofing.
But the roof is only the visible part of a complex system called the roof. The basis of any roof is a reliable and properly designed truss system.
In this material, FORUMHOUSE experts will talk about the main nuances of building a truss system for a wooden and stone house.
From this article you will learn:
- Where does the design of the truss system begin;
- What nuances must be taken into account when installing the truss system of stone and wooden structure;
- What structural elements of the truss system compensate for the shrinkage of a wooden house;
- What features does the truss system of a log house have;
- What is a Mauerlat, and why is it needed in a stone structure;
- What are the requirements for the materials of the wooden truss system;
- What is a truss system built using LSTK technology.
General principles for choosing a truss system for a stone and wooden cottage
Often, novice developers believe that the choice of the design of the truss system can be left "for later", when the walls are already erected. Practice shows that this is fundamentally wrong. Roof even country house- this is a complex system, consisting of many elements. The construction of rafters must begin at the design stage of the house.
Company manager "DDM-Stroy" Vera Vavilova, Moscow:
- The rafter system is the basis (skeleton) of the roof of the house. The quality and durability of the roof directly depends on how competently it will be performed. The manufacture of this structure, especially complex, must begin with its design. This is the only way that will allow you to take into account all the nuances and mount it with high quality.
The service life of the roof largely depends on how competently this structure is selected and mounted. It is also necessary to strike a balance between functionality and design refinements.
Director of company " Smart-Build» Pavel Orlov:
- The design of the truss system begins with the choice of the type of roof - attic or cold attic. For mansard roofs, the angle of inclination of the rafters is made from 35 degrees and above. For a cold attic, the base rafter angle is 25 degrees.
The simpler the shape of the roof, the simpler the design, the faster it is to manufacture, and the builders are less likely to make a mistake. Therefore, it is cheaper to build and easier to maintain a roof that has a simple shape. Big square roofs, the presence of bay windows, the complex polygonal shape of the building significantly complicate and increase the cost of the construction of the truss system - it requires competent design and calculation.
The most cost-effective truss system is for a simple gable roof with a slope of at least 25 - 30 degrees.
The main factors that affect the complexity of manufacturing and final price designs:
- Type of finishing roofing. The choice of one or another coating determines the composition roofing cake, type of crate and load on the truss system. The most popular roofs are metal tiles, soft roofs, CHR ( cement-sand tiles), ceramic or seam roofing;
- The angle of the roof. It determines the loads, and this is the main factor in the design of the structure;
- Will the structural elements (decor element) be visible or will it be completely hidden behind the ceiling lining;
- Large overhangs at the roof significantly increase the cost of the truss system.
If in the design last floor Since the house has large unsupported spans, this entails an increase in the cost and complexity of the structure. In this case, depending on the distances, the truss system is performed using trusses.
- The presence in the project of large chimneys, skylights and other passage elements significantly affects both the complexity of manufacturing the structure and its price.
The design of the truss system (especially complex) should be handled by a person with relevant experience. This design is always calculated for a specific building. A common approach - "I will make a rafter, like a neighbor's" leads to disastrous construction results. The rafter does not withstand loads, which ultimately leads to costly alterations.
The design begins with the collection of expected loads on the roof.
1. Constant values, including the total weight of the roofing, thermal insulation material and fasteners;
2. Temporary values. These are the loads that are exerted on the roof climatic conditions especially snow and wind.
Designers lay the calculated step of the rafters in accordance with the expected load. Let's see how true this is.
Pavel Orlov:
- In my opinion, it is better to choose the pitch of the rafters for attic, well-insulated roofs, based on the size of the insulation - so that the distance between the rafters is 1 cm less than the width of the insulation. This will make it easier to install.
The main load on which the calculation of the truss system is made is snow. Usually, all such structures are designed with a margin, but if there is any doubt (it is supposed to mount a heavy roofing - natural tiles etc.), you can slightly reduce the pitch of the rafters.
Although the snow load is not constant, the rafter must be calculated taking into account the totality of all loads acting on it. The calculation must be carried out not “back to back”, but with some margin in case of heavy precipitation (prolonged snowfall) or increased wind load.
The "work" of the truss system is significantly influenced by the choice of material for the walls of the house.
Features of the truss system in a wooden and stone house
The main difference between the rafters of a stone house and a wooden one is that the stone walls have a structure that is not subject to shrinkage and deformation.
Pavel Orlov:
– The rafters of a stone house do not need deformation elements, since stone house practically does not shrink. main feature the truss system of a stone house is the need for reliable fastening of the Mauerlat. AT wooden houses the role of the Mauerlat is performed by the wall.
Mauerlat is a roofing element (paired boards 50x150, timber 100x150 or 150x150 in size), which is laid around the entire perimeter of the upper wall of the house. The lower part of the rafters rests on the Mauerlat. Thus, the Mauerlat redistributes the point load transmitted from the rafters to the entire area of the upper part of the wall.
Also, when designing the rafter system of a stone house, it is necessary to take into account the thickness of the walls.
Pavel Orlov:
- The design requires the calculation of the permissible lateral load of the rafters on the wall with a fixed mauerlat.
A thin and high wall withstands less side load. This requires application for load-bearing structure rafters of additional elements - retaining racks and girders.
Wooden houses also have their own nuances that must be taken into account when making a truss system.
Vera Vavilova:
- The main feature is that the walls, which are the basis for the rafters, shrink and change their geometry when the weather, temperature and humidity change outside and inside the house.
The main element that compensates for the shrinkage of the walls relative to the rafters is a sliding support (it is also called a sliding support). A sliding support is necessary in order to compensate for the distortions of the truss structure resulting from the shrinkage of wood of natural moisture.
The sliding support is a composite fastener, which includes a bent plate and a corner with a guide.
When the house shrinks, the rafter slides along the guide, thus compensating for all distortions general design rafter system of the house. The sliding part of the support is attached to the rafter beam so that there is a gap between it and the rafter. And the corner with the guide is screwed to the beam.
The slipper must be installed strictly perpendicular to the rafters, with a cut in the timber for the installation of its base. In order to ensure the maximum travel of the slide during shrinkage of wooden structures, during its installation it is installed in the most extreme position.
The degree of shrinkage of a wooden house (and hence the amount of movement acting on the rafters) depends on the material used in the construction of the walls. Natural moisture lumber shrinks more, dry profiled lumber shrinks less, and glued lumber shrinks minimally, etc.
The walls of a house made of dry timber can shrink by 6% of their total height. If we are talking about the walls of a house built from a bar of natural moisture, then shrinkage can be even greater. Our article details what are the pros and cons .
Building a roof on a log house
In addition to timber, wooden houses are built from the so-called log manual felling. Practice shows that the truss system of such a house has its own characteristics.
Dmitry Filippov, company specialist "Traditional Carpentry Technologies":
- In log houses based on a log house, a male-leg roof system is used plus a “sliding” rafter part.
Roof in the house from a log, the device.
The roof for a log house has its own design features. Slegs - horizontal logs cut into a log pediment (the top of them is a ridge) - sit down together with a log house. After that, a lining from a board (aka a ceiling) is laid on the logs (lay down). Next, the rafters are mounted (in gable roofs they are attached to each other on the ridge with sliding fasteners). Then a roofing cake is formed - vapor barrier, insulation, waterproofing, counter-lattice, crate, roofing material is laid on top.
Dmitry Filippov:
- Thus, the rafter part with the roofing cake is not tied to the frame, but, as it were, “lies” on it, which allows the roof to retain its shape and integrity when the frame shrinks.
From our article you will learn about the types of structure and roof shapes of log houses.
Materials going to the rafters
In addition to taking into account the features of wooden and stone houses, when designing a truss system, it is necessary to understand the requirements for lumber.
Vera Vavilova:
- Pine and spruce will do. These are inexpensive and meet the basic strength characteristics of wood rafters.
It is important to follow and make sure that the lumber meets grade 0-2 according to GOST 8486. Rafter elements should not contain large falling knots, rot, wane and cracks. These defects weaken the bearing capacity of the truss system.
Pavel Orlov:
- Apply to the truss system edged wood softwood moisture up to 20%. All lumber used must be treated with certified bio-fire retardant impregnations.
If you put freshly sawn, raw wood on the rafters, then in the process of drying, the already mounted rafters will lead. This will cause deformation of the roof and roofing.
To avoid this, it is better to make rafters from calibrated chamber-drying lumber.
Another option for materials used to make rafters can be trusses and glued beams.
The use of these materials is determined by the project, based on the size of the spans and the expected load on the structure.
Vera Vavilova:
In this case, the elements of the truss system are manufactured at the factory and brought to the site in the form of parts ready for assembly.
This eliminates the so-called "human factor". It also saves time, because such a design is assembled faster than the one that is done on the site with the inevitable sawing and fitting of parts on the spot.
Factory truss systems are made strictly according to the project and specifications. Thanks to this, it is achieved high quality grounds future roof, because the wood has already been treated with antiseptic agents, and the entire truss system is assembled according to the principle of the designer.
Another material used in the construction of truss systems of a stone or wooden house can be light steel thin-walled structures (LSTK). Such a rafter does not need to be treated with antiseptic agents, it has a small weight, long term service and high fire resistance. Consider the main features of the truss system built using this technology.
Deputy commercial director companies "Polymetal-M" Andrey Usachyov:
– The roof truss system, made according to the LSTK technology, includes galvanized rack-mount and guide profiles. If it is necessary to install a warm roof, a thermal profile is used (a profile with perforation along the entire length), which will remove the cold bridge and avoid heat loss.
The thickness and cross section of the profile used in the construction depends on the load that is expected on the truss system.
Each element of the system has strictly specified dimensions according to the project.
This greatly reduces assembly time and also avoids waste at the construction site.
Each profile is marked in accordance with the drawings and assembly instructions.
Andrey Usachyov:
– Thanks to the marking, assembly is simplified. Each profile is marked with a bulge (extrusion). Because the metal frame is fastened together with self-tapping screws, then thanks to the extrusion it is clear where the connection should be. Puklevka increases the rigidity of the assembled node, reducing the force acting on the cut, on the self-tapping screw.
In the FORUMHOUSE topic you can find out what begins. Also here you will find all the information about. Read how to build with your own hands, it is told.
Watch our video about roofing in Russian wooden architecture.
Roof structures are one of the most difficult in the design, installation of residential building units. The roof is the first to take the “blow”, protecting the house from precipitation, wind and cold, so the comfort of all households depends on its tightness, durability, and quality. The foundation reliable roof- a rafter system that gives the structure a shape, sets the optimal slope, and also serves for fastening waterproofing material. Composition and mutual arrangement frame elements depend on the configuration of the roof. In this article we will tell you what types of truss systems are, as well as how they differ from each other.
Rafter system - a set of supporting elements that support the geometry of the roof, frame roof structure, giving it rigidity, the desired slope. The composition, thickness of the section, the location of the parts of the "backbone" of the roof are determined using calculations that take into account permanent and temporary loads. The truss frame performs the following functions that determine the functionality of the roof:
- Specifies the geometry, slope. The rafter legs of the frame give the roof the necessary angle of inclination and shape, contributing to the facilitated descent of snow or precipitation from the surface. It depends on the frame how many tongs or slopes the roof will have, which means it is this structural element that determines it. appearance.
- Serves as a base for attaching waterproofing material. crate roof frame used to fix the roof finish.
- Evenly distributes the weight of the roof. The interconnected elements of the truss system evenly distribute and then redirect the load from the finish coating and the weight of the snow mass between the bearing walls of the structure, preventing skew or deformation of the structure.
- Ensures the functioning of the roof. The structure of the frame, taking into account the features of the device of the roof and roofing, provides support, aeration and protection against condensate.
Please note that a well-designed truss system is a guarantee of durability, reliability and mechanical strength of the roof, so its design and installation is entrusted to professional architects. Experienced craftsmen They believe that a high-quality frame is much more important than a finished roofing, so it’s not worth saving on it.
Criterias of choice
The device of the truss system is characterized by a large number of auxiliary elements and increased complexity. It is compiled according to the calculation of permanent and temporary loads acting on structures, a project that takes into account the selected roofing material, as well as environmental factors. When choosing the type of rafter frame, the following criteria are taken into account:
- Climatic conditions in the region where construction is underway. In order for the roof to withstand the weight of snow and water during heavy rains, the average annual rainfall in winter and summer is determined.
- wind load. To select the optimal roof design, determine the prevailing wind rose in the construction area, and also take into account average speed air gusts.
- The nature of the use of space under the roof. At this stage, it is determined whether a residential attic will be equipped in the under-roof space or an unheated attic.
- Variety of finishes. For each material, the optimal angle of inclination of the slopes is calculated, taking into account its shape and method of attachment.
- Builder's budget. The rafter system is one of the most expensive parts of the roof structure in terms of material and work, so the view is determined by the financial capabilities of the developer.
Experienced craftsmen believe that it is useless to fight nature, you will still lose, therefore, when choosing the type of truss frame, the climatic conditions in the area where the construction is being carried out are at the forefront. If the region is windy, then the angle of inclination of the slopes is made gentle, and if it is snowy, it is steeper.
materials
The truss system is a mandatory element pitched roofs any shape and configuration, consisting of vertical supports, horizontal puffs and rafter legs providing support and secure fastening roofing material. The material used to make the frame must be lightweight, high strength, load-bearing, and resistant to moisture. The most suitable options are:
- Wood. Wood is a natural, environmentally friendly material that is lightweight and durable. For the manufacture of the frame, square bars of 100x100 mm or 150x150 mm are used, boards with a section of 50x150 mm of hardwood. A significant disadvantage of wooden frame elements is that they bend under their own weight at a large length, and also have poor resistance to moisture.
- Metal. Metal truss systems are more expensive than wooden ones, they are used mainly with a large area of slopes and big weight roofing material. High bearing capacity metal profile or corner allows you to increase the step between the elements of the frame without losing structural strength. To reduce the likelihood of rust spreading, corrosion-resistant types of metal are used.
Note! Wood is considered the most suitable material for the manufacture of the roof truss frame of residential buildings, as it has 3 important qualities: light weight, strength, breathability. To increase the resistance of wood to moisture, it is necessary to treat the elements of the truss system with a deeply penetrating antiseptic.
Device
The device of the roof truss system consists of many interconnected elements that, supporting each other, give the structure rigidity, the necessary strength, and also distribute the weight of the roofing material evenly between the bearing supports. The composition of the frame, the size of the section of individual elements and their placement depend on the type of finish coating, the slope of the slope and the method of using the under-roof space. The framework usually consists of:
- Mauerlat. Mauerlat is called a rafter beam, which is mounted on top of the upper crown or a number of load-bearing walls of the house. It is made from durable, solid pine wood. The Mauerlat is fastened with long metal studs or anchor bolts.
- Lejeune. Lying is called a Mauerlat beam, located not on the external load-bearing walls, but on internal partitions. Central racks are installed on the bed to support the roof ridge.
- Rack. Racks are called vertical supporting elements, which support the ridge run or the central part of the rafter legs of the frame.
- Rafter. The rafter legs rest on the Mauerlat and the ridge run, located at an angle to the base of the roof.
- Rigel and puffs. These terms are called horizontal elements of the frame, pulling the rafter legs together in pairs. The crossbar is located at the top of the rafters, right under the ridge, it is thicker and stronger than the puff, which is located much lower.
- Podkosov. The strut is set at an angle to the rafters to prevent them from bending under their own weight. At one end, they rest against the leg, and at the other end, against a rack or puff.
Important! The simplest rafter system consists only of a mauerlat, rafters and a ridge run. With an increase in the complexity of the roof, the number of additional elements increases, strengthening the structure, as well as compensating for deflection and expansion loads.
Kinds
The configuration of the roof frame depends on architectural features covered building. The roof must take into account the number of bearing supports inside or outside the house in order to evenly distribute the load placed on them. Distinguish the following types rafters:
Please note that the final appearance of the truss frame made of wooden or metal elements depends on the number of slopes and the type of roof. The simplest options are single-sided and gable roof, and complex - hip, half-hip, tent.
Video instruction
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):
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 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. because of sharp corners there are "blind" zones that are unusable.
The device of one angle 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.
This roof design 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 requires knowledge of the purpose of the main structural elements.
The locations of the elements are shown in the photo.
- 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 age of the structure. 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.
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 on attic loft- 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.
- 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 device to the gable roof truss system diagram ventilation shaft and chimney.
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 quality wood no damage or 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
Calculation of material parameters milestone, therefore, we present the calculation algorithm step by step.
It is important to know: the entire truss system consists of many triangles, as the most rigid element. In turn, if the slopes have 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 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. Average value 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. Valid in different periods and with different strengths. These 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.
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, to a private house surrounded by high-rise buildings, there are fewer loads. Standing separately Vacation home or cottage experience 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.
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 large quantity roof trusses and rafter elements are needed to create the necessary margin of safety.
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 influences total cost works.
Nuance. The minimum slope angle of a gable roof must be at least 5°.
5. Calculation of the pitch of the rafters
Gable roof rafter pitch 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.
Rafter length for attic roof 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 is worth noting that maximum length timber - 6 m.p. 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.
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. How more step installation of rafters, the greater the load falls 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;
- bed - 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.
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, allow you to reduce its influence. The puff in the truss system can be wooden or metal. Often puffs are placed at the bottom, then they play a role 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 configurations, it is used combined view rafter 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. Get a kind step-by-step instruction, which contains additional information for each step.
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 Mauerlat plays top crown. In buildings built of 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.
The material was prepared for the site www.site
Since the length of the Mauerlat exceeds standard sizes 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
Anchor bolts. Ideal for monolithic construction.
Wooden dowels. Are used for fellings from a log and a bar. But, they are always used with additional fasteners.
Staples.
Stud or armature. It is used if the cottage is built of porous materials (aerated concrete, foam concrete).
Sliding fastening (hinged). The bundle in this way allows you to ensure the displacement of the rafter legs when the house shrinks.
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. The downside is that the weight assembled structure roof truss 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.
Start installation rafter pairs you need 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 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 on what needs to be done series installation 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.
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.
Advice. The way in which the Mauerlat is extended (washed down at 90 °) in this case cannot be applied. 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.).
- 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.
- More modern variety manufacturing a ridge knot can be considered the method shown in the photo.
- Cutting method.
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 a professional flooring and slate - 440 mm.
- under 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 robust design with your own hands.
Perhaps the main decoration of any house is the roof, without which it is difficult to imagine any structure. The roof gives the private house a holistic appearance and defines its style. However, it primarily acts as engineering structure designed to protect people from destructive impact external environment.
Today, the use in the construction of houses of various elements of architecture, undeservedly forgotten earlier, is returning to fashion. For example, more and more often there are mezzanines, bay windows, attics, giving the building a stylish and interesting exterior. At the same time, a noticeable increase in internal space can be achieved at a relatively low cost of funds.
The roof truss system is considered the most strong, durable construction. It is characterized by ease of installation, ease of adjustment and the ability to withstand heavy loads, with a relatively light weight. The rafter system is a special design, with a triangle at the base. Its rigidity is achieved by attaching the rafters and the roof frame to each other. The most common options are made of wooden logs or beams, however, there are also systems made of galvanized steel.
Types of truss systems
Experts distinguish between several varieties of truss systems. They are accepted classify according to the shape and type of roof:
- four-slope;
- tri-slope;
- gable;
- hip;
- half hip;
- broken lines.
Gable truss system roofing is the cheapest and easiest option. The main advantages of this design include simplicity, reliability and the ability to withstand significant loads. At the same time, it is worth describing some of the shortcomings. Namely, the impossibility of implementing any special design solutions due to the simplicity of the shape of such a roof. However, this minus can easily be compensated by decorating the house with various decorative elements. The second disadvantage can be called more significant - inner space small size, significantly different downwards from the parameters of a sloping roof.
The most common and recognized among fans of interesting architectural solutions, is sloping roof truss system. In this case, there is an opportunity for the manifestation of imagination, of course, subject to the established building standards and strength characteristics. This design can be regular or asymmetric in shape and is determined based on the structure of the house itself, as well as the design and layout of the interior of the room.
Sometimes you can get extremely interesting room under the roof, correctly installing the truss system and organically using a second light or mezzanine. In order for relatively small financial costs maximize usable area at home and make it cozy, it is very important to be able to effectively and fully use the available space.
Features and requirements for the truss system
The size of the rafters, which are elements that determine the strength and slope of the roof, must be calculated individually for each private house, taking into account total area and geometric shape roofs, as well as the distance between the walls. Depending on the results obtained, it will be possible to determine the appropriate section of the bars. As a rule, this figure is about 1 meter.
In practice, apply two types of rafters:
- An inclined structure that rests on the walls of the house along the entire perimeter, and in the center it is supported by an additional or intermediate support. It is advisable to use if the distance between several supports is not more than 6.5 m.
- Hanging rafters, fixed at the top of the ridge and resting against each other. This system is characterized by a special reliability of the connection of the walls to each other.
In general, the device of the truss system directly depends on the type of material from which the house is made. For example, for a building built of bricks, a truss system is recommended, which rests on a separately constructed support of small cross-section beams or Mauerlat. As a support for the rafters of a wooden structure, the upper crown of the log house is best suited, and for houses frame type use the top harness.
The main parts of the roof truss system
The basis of the roof on which roofing pie installation and inner lining premises, is precisely the truss system. Often it is also used as a basis for communications and engineering systems. Aggregate various nodes and the elements that make up the device of the roof truss system, performs the function of transferring power loads directly from the roof to the load-bearing walls of the structure. The main parts include:
- Hanging and inclined rafters.
- Mauerlat.
- Skate and side runs.
- All kinds of connecting elements, such as struts, diagonal braces, spacers.
As a rule, the load on the roof truss structure is very high. It is determined individually design features roofs and peculiar to the area, wind and snow loads. The installed rafters must guarantee the retention of such loads, and also have the necessary margin of safety to withstand possible gusts of wind or snowfall.
In order to determine the main parameters of the nodes of the roof truss system, it is necessary perform special calculations. They will help to accurately determine the profile, length and cross section of each of the structural elements, as well as the features of the interaction between the parts. The strength of the entire structure largely depends on how tightly the nodes of the roof truss system are connected. It is recommended to apply the following types of connections:
Which type of connection is applicable for a particular system can be determined based on the design load, design features and materials used.
Mounting principles
Installation work carried out in three main stages. In particular, location-aware markup window openings, hoods, chimney, mounting the Mauerlat and securely fastening it to the bearing support. Next, the roof trusses are erected and, finally, the ridge is installed.
Installation should begin with laying the Mauerlat walls on top and attaching the rafters directly to it. They must be installed in the desired position and fixed at one end to the support, and from the other to the ridge beam. For reliability, the connections can be fixed to each other additionally with studs with a diameter of 8-12 mm.
When constructing a truss structure, the most common an error is a miscalculation rafter sizes, which can lead to roof sagging.
To provide for each element and node, to deal with the technology, it is necessary to preliminary stage. At the same time, it is also recommended to plan a cornice overhang with a length of 60 cm or more, which will reduce the effect of weather phenomena on the walls of the house.
For wooden structures that can dry out over time, the most appropriate mounting option would be bolted connections that can add rigidity to the entire structure.
Subject to all the basic rules, the installation of the roof truss system can be performed relatively easily. However, it is important to strictly adhere to the chosen technology in order to avoid the risk of various problems.
