Building a house is fraught with many nuances, which many novice builders do not even know about. In particular, one of these "pitfalls" is the floor unit, which is a whole technology responsible for the durability of the house.
That is why it is necessary to approach the solution of this problem with all responsibility, at least to get acquainted with the consequences of negligence.
Introduction to slab nodes
Node for supporting the floor slab on brick wall is nothing more than a junction of two planes: vertical and horizontal. Many private developers play this moment in different ways, but it does not always work out correctly, and even more so reliably.
Therefore, in order to avoid the adverse consequences associated with expensive repairs, it is necessary to prepare in advance.
Types of materials used for floors
By themselves, these ceilings are made of reinforced concrete slabs, the most reliable materials available.
There are just some differences in manufacturing process, this is related to the type of structure:
- Cellular concrete.
- Precast-monolithic- the most popular of all presented.
- Made on the basis of heavy concrete. This type refers to many materials, since impurities of heavy concrete are present in various products.
- multi-hollow.
All of the above-described floors of brick buildings are used under certain conditions, depending on the construction plan, the load being carried out and the dimensions of the span.
They should be divided into two categories:
- Interfloor ceilings in brick house- used for multi-level houses. They are mounted in a load-bearing wall on a special lining that provides reliable fixation of the product. In this case, the depth with which the ceiling will lie on the wall is very important.
- The attic type does not experience such high loads, therefore it is mounted in the wall without lining.
Note! If you decide to build a multi-storey brick house with your own hands, you should give your preference to the ceiling of prefabricated reinforced concrete slabs. They have not only increased strength, but also a huge bearing capacity, as well as, if I may say so, affordable installation.
Support node - we find a solution
So that the support of floor slabs on brick walls can withstand high loads, little use of durable materials, the most delicate approach is required here.
- Firstly, it is necessary to correctly calculate the support node. Keep in mind that it can only be implemented on a load-bearing wall, but cannot be connected to a partition in any way.
Note! Each product ( construction material) has its own marking, which indicates its certain features: seismic resistance, bearing capacity and others. This applies not only to reinforced concrete slabs, but also to bricks used as load-bearing structures. For example, double silicate brick M 150 - not the most the best solution for the construction of a multi-storey building.
- Secondly, all calculations and a plan for solving the problem must be verified with GOST 956-91 and additional design documents. Otherwise, you may be denied construction.
For example, look at the marking of PK 42.15-8T slabs, where PK is a floor with round voids, 42.15 is the dimensions of the product in decimeters (length 4180, width 1490). The number 8 is the maximum allowable load on the slab, which is 800 kgf / m2, and the letter T following 8 is the index of heavy concrete used for the production of this slab.
There is also a certain standard for how the floor slabs should look like on a brick wall - from 90 to 120 mm. It is this size that should be maintained, adjusting to it.
There are two main points to consider here:
- The reliability of the foundation of the house, which must be designed for high loads. It is necessary to avoid those places where the foundation can be weakened, which will lead to uneven shrinkage of the structure, as a result of which - curvature of the floor.
- The width of the foundation should in no case be less than the brickwork. In this case, the deformation bearing walls inevitable - the load of the floor will affect the bricks, the weakening of the cement mortar.
It is also necessary to focus on the thickness of the slab in relation to the thickness of the bearing wall. And this is on condition that a high-quality building brick, which meets the standards and GOSTs.
Fixing floor slabs
Anchoring floor slabs in a brick house is used to strengthen the structure, increase strength and reduce the likelihood of material deformation. This method is extremely difficult to implement on your own, so it is better to entrust it to professionals, although the price can be unpleasantly high. The main thing in the construction business is reliability and durability.
One feature to be aware of is that the location of the anchors is possible through the slab. However, there is a limit - 3 meters apart, this is the maximum allowable.
Note! The anchor is also used to fasten precast concrete slabs together.
Now you understand what a node for supporting a floor slab on a brick wall is, what is connected with it and what it affects. That is why you can protect yourself from any adverse moments at the design stage.
Conclusion
It is important not only to lay the slabs correctly, but also to build a foundation, to withstand the drying time of the mortar, to lay bricks with a minimum joint thickness, as the instructions say. You can do all this yourself, but if in doubt, it is better to entrust the work to professionals.
The cover is one of structural elements buildings dividing it inner space to the floors. The ceiling refers to the bearing elements, as it perceives and transfers the load from its own weight, as well as from equipment and people to walls, supports, crossbars. It is made of reinforced concrete slabs.
By location in the building, they can be divided into:
- Above basement.
- Interfloor.
- Attic.
According to their design, they are divided into beam and beamless. They are factory-made from reinforced concrete and are divided into precast-monolithic, multi-hollow, made from heavy concrete and cellular concrete. Overlappings must meet such requirements as strength, soundproofing, rigidity, fireproofing and watertightness.
Mostly reinforced concrete slabs, from which the floors are made, are multi-hollow structures and are produced with polygonal, oval and round voids. The most widespread in construction are slabs with round voids PNO and PK, the bearing capacity of which is 800 kg / m2. They are distinguished by high strength, complete factory readiness for installation, manufacturability. Such plates are supported on two sides. Lay them on load-bearing walls. Ceilings from such slabs are used with a step of load-bearing walls up to 9 m. Durability, fire resistance, necessary spatial rigidity, building stability - this is what distinguishes such ceilings.
Common standards for hollow core slabs:
- length - 2.4-7.2 m;
- width - 1-1.8 m;
- thickness - 220 mm.
The base on which the slabs are laid can be from:
- bricks;
- reinforced concrete panels;
- aerated concrete;
- foam blocks.
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The depth of support of the ceiling and the necessary equipment for work
Depending on the basis on which, the value of the depth of support is taken into account.
Also taken into account in without fail the length of the slab, its weight, the thickness of the supporting wall, the permanent or temporary load on the slab from above, the seismic resistance of the building. The calculations are quite complex and are done by specialists. It is enough for an individual developer to focus on the parameters of the manufacturer marking their products and follow them clearly. Accurately following the recommendations of manufacturers will eliminate errors in the design and installation of hollow structures, otherwise the consequences will entail costly and labor-intensive steps.
- on large-panel walls - 50-90 mm;
- on brick walls - 90-120 mm;
- on aerated concrete base - 120 mm;
- on foam block walls - 120 mm;
- on external walls, the support is stipulated up to 250 mm.
Necessary equipment, materials and tools:
- anchors;
- cement mortar;
- level or level - to determine the height difference between the working surfaces;
- crossbars - support beams;
- mounting crowbar;
- plumb - to check the verticality of the surface;
- inventory scaffolding;
- mooring cord;
- slings;
- truck crane with a lifting capacity of 25 tons.
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Installation of floors in brick buildings
For installation work Requires a team of four. The crane driver delivers to the base (walls) - a slab. The rigger is busy slinging the plates with a four-branch sling. Two installers, being on both sides of the supports of the plate to be mounted, receive it, turn it around and then coordinate its lowering to a predetermined position with guiding actions. After mounting crowbars, they perform a small straightening of the slab, even before removing the slings.
In brick buildings they are laid on walls and crossbars. Crossbars are laid on reinforced concrete pillows using slings. They must be laid in brick walls during masonry. Before placing the crossbars, it is necessary to check the horizontality of the pillows. The difference between them, or rather, their surfaces, should not exceed 10 mm. Then the crossbars are brought to the desired position with mounting crowbars. The installers themselves are located on the scaffolds. The crossbar must be moved only along the perpendicular to the longitudinal axis, using the blade of the mounting crowbar. Otherwise, the stability of the walls that support the crossbar will be violated. After that, verticality (plumb) and horizontal (level) is reconciled, and only then the crossbar is fixed to the base. When these works are completed, the slings are removed.
The use of hollow core slabs is possible in buildings with either transverse or longitudinal load-bearing walls, because they are supported on two sides. Then follows the anchoring of the floor, which is the fastening of the laid floor slabs with the outer walls and among themselves. Anchors are usually placed at a distance of no more than 3 m from each other.
Before laying the floor slabs, the horizontality of the working surfaces is again verified. Be sure to level the crest of the masonry wall. Because enough big square hollow floors will be sensitive to even small irregularities in the base. The plates will just swing. Identified irregularities are laid with additional strips of insulation.
And only after that they fall on the slab supports, where the cement mortar has already been placed. In order to obtain a single rigid horizontal overlap, the plates are connected to each other and to the outer walls with steel anchors, which are fixed to the mounting loops. The ends of the floor slabs are connected to the masonry of the brick wall with L-shaped anchors. Then they are sealed with a mortar mixture in order to protect against corrosion.
When the plates are supported on the internal walls, then composite anchors are used, obtained by connecting them by welding. The gaps that appear between the slabs are filled with bricks used in the main masonry. Plates are laid on the mortar mixture.
The ceiling after laying the slabs is checked for horizontality. If a discrepancy is found between adjacent plates, they are lifted with a crane and the mortar bed is trimmed, after which they are again laid in place. When the alignment is completed, the plates are fixed with anchors, which are laid in the masonry. Adjacent plates are interconnected by mounting loops with anchors.
In hollow decking, if the support goes to the outer base, the voids are filled with heavy concrete or concrete plugs by about 12 cm. This is done for the purpose of insulation. The same is done in the hollow containers of the slabs, which are supported by internal load-bearing walls. The voids are filled to prevent destruction supporting parts pressure plates of structures located above, since it is their edges that are the most fragile.
Jumpers that are load-bearing, that is, those on which the main load from the ceilings falls, are installed by lifting them with slings for mounting loops and laying them on the mortar mixture. Ordinary jumpers are placed manually, taking into account the area of \u200b\u200bsupport and horizontality.
For different types buildings use certain types of floors. During the installation process, it is necessary to comply with the laying technology, which is regulated normative documents(SP 70.13330.2012).
Types by way of support
The slab used for interfloor separation is a reinforced reinforced concrete structure, with voids. There are holes in the plates to lighten the weight of the structural element.
The choice of interfloor overlap and the depth of its support depends on design features building. The following parameters are taken into account:
- purpose of the building (residential, industrial, public);
- the material from which the structure was built;
- wall thickness;
- types of loads acting both on the slabs and on the building;
- seismic characteristics of the building area.
By type of support interfloor slabs divided into three categories. Their choice is carried out at the project planning stage, taking into account the calculations of the loads acting on load-bearing elements building.
On two sides
The support for such slabs are two opposite load-bearing walls. They are laid on capital elements, with narrow (transverse) sides. Most often, for this type, interfloor ceilings with round voids are used, marked PC, 1PC, 2PC. They are able to withstand loads up to 800 kg/m².
On three sides
They have reinforced end reinforcement and are laid on three load-bearing walls. They are mounted in the corners of the building, having a U-shaped design of load-bearing walls. They are marked with the PKT marking, and withstand loads up to 1600 kg / m².
on four sides
Such plates are reinforced with reinforcement along all ends, they are more rigid and have an increased bearing capacity. Used only in complex structures where maximum distribution of high loads is required, or in cases where additional superstructures are planned to be erected. They have the PKK marking, indicating increased strength. In low-rise construction, they are practically not used.
For low-rise, as well as private construction, it is recommended to use round and oval-hollow floor slabs, with support on both sides.
Depth of the institution on the walls
All floors, regardless of the method of installation, can be laid on a foundation or load-bearing walls made of bricks, reinforced concrete panels, or foam blocks.
The support depth is the distance that the slab rests on the supporting element.
It is important to know how much a hollow reinforced concrete product can be supported on. This depth depends on the material from which the supporting structures are built.:
- brick - from 9 to 12 cm;
- panel - from 5 to 9 cm;
- aerated concrete or foam block - from 12 to 25 cm.
Failure to comply with the recommended laying depth is fraught with the destruction of the walls, due to improperly distributed loads. Insufficient depth leads to coloring of the inner layer of masonry and plaster, or to cracking of panels. Excessive distance taken under the support will lead to the destruction of the outer part of the wall.
Scheme of the correct and incorrect support node on a brick wall:
Excessive depth of bearing on the load-bearing wall creates cold bridges and improper distribution of loads, which, accordingly, leads to large heat losses and leads to the gradual destruction of the building.
Excerpt from SNIP
JV “Large-panel structural systems. Design Rules»
4.3.17 The depth of support of prefabricated solid slabs on concrete and reinforced concrete walls, depending on the nature of their support, is taken at least:
- 40 mm - when supported along the contour, as well as two long and one short sides;
- 50 mm - on two sides and a span of 4.2 m or less, as well as on two short and one long sides;
- 70 mm - on both sides and a span of more than 4.2 m.
Support of hollow-core slabs without formwork molding on Wall panels it is made on two sides, that is, according to a beam scheme with a support depth of at least 80 mm for slabs with a height of 220 mm or less, and at least 100 mm for slabs with a height of more than 220 mm.
In all cases, the maximum support depth of formworkless hollow core slabs is assumed to be no more 150 mm.
Support on three or more sides of hollow-core slabs without formwork molding (insertion of the longitudinal side of the slabs into the walls) not allowed.
armored belt
Before installing floors on the main structures,. It is performed along the perimeter of the area of \u200b\u200bthe main walls, over their entire width. Formwork is installed along the edge, then a reinforced frame is mounted from longitudinal, transverse and vertical reinforcing bars, and poured with concrete.
During the construction of the armored belt, the following requirements must be met:
- The height of the armored belt is from 20 to 40 cm (not less than the height of a standard aerated concrete block).
- The width must match the width of the carrier element.
- The thickness of the reinforcement is not less than 8 mm. The frame is rigidly knitted with wire or fastened by welding.
- Concrete must match the brand of mortar used in masonry. The recommended brand of concrete used is at least class B15.
The armored belt serves to evenly distribute all loads. It also installs reinforcing fasteners, which are designed for reliable installation of interfloor ceilings. Since the armo-belt is a cold concrete layer, it is provided for the arrangement of a thermal insulation coating.
Attention!
Floor slabs are mounted only after the complete drying of the monolithic reinforcing belt.
Support nodes
Support nodes are the places where the plate is attached to supporting structure, or joints of vertical and horizontal elements of the building structure.
They are designed for reliable and correct fixation of floor slabs on capital elements. The laying of the slab and its fixing on the wall is carried out using mortar and rigid reinforcing joints.
Nodal connections must meet the following requirements:
- the end sides of the plates should not closely adjoin the masonry;
- thermal insulation is performed between the masonry and the ceiling;
- hollow holes are recommended to be closed with special inserts to prevent heat loss;
- the connection of the ceiling and the armo-belt is performed by rigidly connecting the armo-belt reinforcement with the reinforcing rods of the slab by welding.
Nodes depend on the number and type of capital elements. For support on two sides, they are carried out on transverse load-bearing walls, and for support on three or four sides - on both transverse and longitudinal walls. Knots are also performed when columns, trusses and floor beams act as load-bearing elements.
In areas with increased seismic activity, it is recommended to carry out support units using movable hinged joints.
When laying floor slabs, it is necessary to take into account all the parameters necessary for their correct support on the bearing elements. The choice of slabs, the calculation of knots, armored belts and the depth of support are made at the design stage of the building.
Useful video
The video clearly explains why it is impossible to support with a deep institution in the wall. Only I would argue with the value of the maximum depth of 30 cm. It should be no more than 15 cm.
The ceiling is supported on aerated concrete by means of special armored belts. Its manufacture is necessary to receive loads from gravity and construction materials next floors or roof. What is an armored belt? This is a monolithic structure made of reinforced concrete, following the contours of the walls. The armored belt is erected on load-bearing walls, which are built using aerated concrete.
To fill the armored belt, a formwork for concrete is prepared, which is a structure for creating a form in which reinforcement is placed for rigidity.
If the slabs are supported on the internal walls of the house, the walls are built in such a way that they rest on the foundation. Armopoyas on internal walls under the floor slabs reinforces the structure, as the load is distributed over the entire area of the slab. An armored belt is not considered a construction made brickwork on aerated concrete, as well as strengthening aerated concrete masonry reinforced mesh.
For supporting floor slabs, the following requirements are imposed:
- ceilings and coverings should be installed on anti-seismic belts;
- connection of plates and belts must be mechanically strong using welding;
- the belt should line up the entire width of the wall; for external walls of 500 mm, it can be reduced by 100-150 mm;
- for laying the belt, it is necessary to use concrete with a class of at least B15.
Support depth
The support of the floor slab on the wall must be at least 120 mm, and reliable adhesion of the slab to the bearing wall must also be ensured.
To fill the armored belt, reinforcement is preliminarily installed, the number and location of which is determined by calculations. On average, at least 4 rods of 12 mm are accepted. If aerated concrete will not be insulated, but only plastered, then the belt is not made across the entire width of the wall, but less by the thickness of the insulation layer.
The armored belt must be insulated, as it is a bridge of cold. The formation of such a bridge can destroy aerated concrete due to the accumulation of moisture. When reducing the thickness of the armored belt, one should not forget about the minimum depth of support of the plates on the walls.
The depths of support of the slabs on the walls have normalized values:
- when supported along the contour of at least 40 mm;
- when supported on two sides with a span of 4.2 m or less, at least 50 mm;
- when supported on two sides with a span of more than 4.2 m, at least 70 mm.
By observing these distances, you can be sure that your house will not collapse.
The purpose of the armored belt
When arranging the places of support for floor slabs, it is necessary to take into account the thermal performance of the walls and the materials from which they are built.
So is an armored belt really necessary to support floor slabs on aerated concrete? Let's try to figure it out.
Firstly, the armo-belt increases the resistance of the structure of your house against deformation by loads of various kinds. For example, shrinkage of the structure, precipitation of the soil under it, temperature changes during the day and the change of season.
Aerated concrete does not withstand high loads and deforms under the action of external applied forces. In order to prevent this from happening, armored belts are installed that compensate for the load. Armopoyas takes on the entire load, thereby preventing the destruction of the structure. Aerated concrete does not withstand a point load, so fastening wooden beams during the construction of the roof is very complicated.
The armo-belt provides a way out of the situation. The second name of the armored belt is unloading (because of its ability to evenly distribute vertical load). Its use allows you to give rigidity to the structure. With the movement of steam and moisture, aerated concrete, as a porous material, can expand, which can lead to the movement of floor slabs.
Given these factors, we can firmly say that the armored belt for supporting the floor slabs of the next floor or roof is simply necessary. Otherwise, with any level deviation, a point load is laid out on the aerated concrete, which deforms it and destroys it.
The process of building an armored belt is not too laborious and costly, while it will keep your home longer.
Production of armored belt
The armored belt is equipped around the entire perimeter of the building, while the reinforcement is connected by welding or knitting with a special wire.
In order to start work on the construction of the armored belt, you need to prepare tools and accessories:
- hammer and nails for assembling timber formwork;
- reinforcement for frame assembly;
- welding machine for welding reinforcing bars at corners and at joints;
- container, bucket, spatula for pouring mortar into the formwork.
Erected, moreover, under the floor slab, under the roof to facilitate the installation of the roof. If it is planned to build an attic in your house, then for its slabs it is also necessary to increase the rigidity of the base.
To fill the armored belt, aerated concrete and formwork are prepared. The formwork is a structure for creating a form, which will later be poured with cement mortar. Formwork units:
- the deck that comes into contact with the concrete gives shape and quality to the face;
- the woods;
- fasteners that hold the system immobile at mounting level and connect individual elements between themselves.
For the construction of an armored belt for supporting floor slabs, horizontal formwork is used. The formwork material can be steel (sheet), aluminum, wood (board, plywood, the main condition is low hygroscopicity), plastic. If necessary, formwork materials can be combined.
Lightweight and available material for formwork is wood.
If there is no time to prepare the formwork, you can spend money and rent it. Today there are many construction companies who provide such a service.
How to make formwork? The design of the formwork is not very complicated. Use boards 20 mm thick, 200 mm wide - this is optimal dimensions. Excessive width can lead to the destruction of the formwork as a result of the appearance of cracks. It is recommended to wet the board before use. Boards of wooden formwork elements are tightly connected to each other. At the same time, avoid large gaps.
If the gap is up to 3 mm wide, you can get rid of it by abundantly moistening the boards. The material swells and the gap disappears. With a slot width of wooden elements 3-10 mm, it is recommended to use tow, if the gap is more than 10 mm, then it is clogged with slats. Horizontal and vertical formwork is controlled by building level. This is necessary for the evenness of the filling of the armored belt and the further location of the floor slab on the belt. With repeated use wooden shields you can wrap them plastic wrap, this will also get rid of wide gaps.
The smoother the board used in the manufacture wooden formwork, the more geometrically even the armored belt will be.
Reinforcement is placed in the formwork. Ideal option the use of four rods with a diameter of 12 mm or a finished reinforcing cage is considered. The minimum requirements are the laying of two 12 mm rods. Reinforcing bars are connected with a "ladder" with a step of 50-70 mm. At the corners, the reinforcement is connected with steel wire or welding. The ladder is obtained by installing jumpers between two solid rods.
With a large load from the plates, a three-dimensional frame structure is used. In order for the frame to be made not to touch the aerated concrete blocks, it is laid on pieces of bricks or blocks. Before pouring the solution, the location of the frame is checked by level. Having prepared the solution, the armored belt is poured. For the solution, 3 buckets of sand, 1 bucket of cement and 5 buckets of crushed stone are used. For the convenience of work, small gravel is used.
If the work on the installation of the armored belt is planned to be phased, then the filling is carried out according to the principle of vertical cutting off. That is, the frame is completely poured in height to a certain place, then the jumpers are set. The material for the jumpers can be a brick or a gas block.
Work is suspended. Before further work the jumper material is removed, the frozen filled part is well moistened with water, as this provides best connection. The pouring of concrete should be carried out without the formation of voids; for this, the surface is leveled with reinforcement.
Formwork can be dismantled after 3-4 days.
On the received armored belt. In practice, multi-hollow slabs made of heavy concrete, cellular concrete, precast-monolithic are used. They are selected based on the size of the span and bearing capacity.
Most often, multi-hollow slabs PK and PNO are used, the bearing capacity of which is 800 kgf / sq.m. The advantages of such floor slabs include high strength, manufacturability and complete factory readiness for installation.
The support of the floor slab on the armored belt of a gas-block structure should be 250 mm. The usual support is 120 mm.
Armopoyas in openings
The creation of an armored belt over the openings has small features. In this case, the support of the slab will be incomplete, since the ceiling hangs over the void. To support the slab, pillars are erected with lintels in the form of beams.
Pillars can be built with bricks, blocks. Each pillar is laid out in one and a half bricks.
Reinforced concrete lintels are erected between the pillars. The height of the beams should be 1/20 of the length of the opening. If the distance between the posts is 2 m, then the height of the beams will be 0.1 m. The width of the beams will be determined, the height from the ratio 0.1 m = 5/7. If the distance between the supports is 2 m, and the height of the beams is 0.1 m, then the width reinforced concrete beams is 0.07 m. For pouring beams use removable formwork from boards.
When building a house, any developer faces the question of choice interfloor overlap. The most common are three types of floors - wooden, monolithic reinforced concrete and prefabricated reinforced concrete, mounted from flat hollow core slabs. It is about this type of overlap, as the most popular and practical for low-rise construction, will be discussed in this article. From this pro interfloor ceilings in a private house you will learn:
- What is the difference between hollow-core floor slabs (PC) and floor slabs made by formless molding (PB).
- How to properly lay floors.
- How to avoid installation errors.
- How to store floor slabs.
How to choose a hollow core slab
At first glance, hollow core slabs may seem to differ only in length, thickness and width. But specifications hollow core slabs are much wider and are described in detail in GOST 9561-91.
Hollow core slab, private house.
Hollow interfloor slabs differ from each other by the method of reinforcement. Moreover, reinforcement (depending on the type of plates) can be performed using prestressed reinforcement or without prestressed reinforcement. Most often, ceilings with prestressed working reinforcement are used.
When choosing floor slabs, you should pay attention to such important point, as the allowable number of sides on which they can be leaned. . Usually you can only support on two short sides, but some types of plates allow support on three and four sides.
- PB. Provides support on two sides;
- 1pc. Thickness - 220 mm. The diameter of the round voids is 159 mm. Allows support only on two sides;
- 1PKT. Having similar dimensions, it allows support on three sides;
- 1PKK. Can be leaned on four sides.
Also, floor slabs differ from each other by the method of manufacture. Often there is a dispute about what to prefer - PC or PB.
Andrey164 FORUMHOUSE user
It's time to cover ground floor buildings with floor slabs, but I just can’t determine what to choose - PC or PB, PB has a better surface finish than PC, but I heard that PBs are used only in monolithic-frame houses and country houses, and the end of such a plate cannot be loaded with a wall.
Sasha1983 FORUMHOUSE user
The main difference between the plates lies in the technology of their manufacture.
PC (thickness from 160 to 260 mm and a typical bearing capacity of 800 kg / sq.m.) is cast in the formwork. PB brand panels (thickness from 160 mm to 330 mm and typical bearing capacity from 800 kg/sq.m.) flat surface than PC panels). PB is also called extruder.
PB, due to the prestressing of the compressed and stretched zones (prestressing of the reinforcement is done at any length of the plate), are less susceptible to cracking than PC. PC with a length of up to 4.2 meters can be produced without prestressed reinforcement and have a greater free deflection than PB.
At the request of the customer, the PB can be cut to individual specified dimensions (from 1.8 to 9 meters, etc.). They can also be cut lengthwise and into separate longitudinal elements, as well as bevel cuts at an angle of 30-90 degrees, without losing its load-bearing capacity. This greatly simplifies the layout of such floor slabs on construction site and provides more freedom to the designer, because the dimensions of the building box and load-bearing walls are not tied to standard sizes PC.
When choosing interfloor PC slabs (more than 4.2 meters long), it is important to remember this feature - they are prestressed with special stops at the ends of the slab. If you cut off the end of the PC, then the stop (cut off together with the end of the PC and vertical reinforcement) will not work. Accordingly, the working reinforcement will cling to concrete only with its lateral surface. This will greatly reduce bearing capacity plates.
Despite the higher quality smooth surface, good geometry, lower weight and high load-bearing capacity, this point should be taken into account when choosing a PB. Hollow holes in the PC (depending on the width of the plate, with a diameter of 114 to 203 mm) allow you to easily punch a hole in it for a sewer riser, with a diameter of 100 mm. While the size of the hollow hole in the PB is 60 mm. Therefore, in order to break through through hole in the panel of the PB brand (in order not to damage the fittings), you should check with the manufacturer in advance how best to do this.
Floor slabs for a private house: installation features
The PB (unlike the PC) does not have mounting loops (or you have to pay extra for their installation), which can complicate their loading, unloading and installation.
It is not recommended to use the "folk" method of installing the PB, when the mounting hooks cling to the end of the hollow hole. In this case, there is a high probability that the hook will pull out of the hole due to the destruction of the end of the plate, or the hook will simply slip off. This will cause the plate to fall. Also, at your own peril and risk, you can apply a method in which a crowbar is inserted into the hollow holes of the PB (two crowbars on one side of the plate) and hooks cling to them.
Installation of PB plates is allowed only with the use of soft chocks or a special traverse.
ProgC FORUMHOUSE user
To pull the chalk out from under the slab, laying it down, leave a gap of 2 cm to the adjacent slab. Then we shift the already laid slab with a crowbar to the next one.
Max_im FORUMHOUSE user
Personal experience: I laid slabs at my construction site using this method. The gap was 3 cm. The slabs were laid on a cement-sand mixture 2 cm thick. The mixture acted as a lubricant, and the slabs were easily moved with a crowbar to the distance I needed.
Also, when installing floor slabs, it is necessary to observe the calculated values of the minimum support depth of the slab. The following numbers can be used as a guide:
- brick wall, minimum support depth is 8 cm, maximum support depth is 16 cm;
- reinforced concrete - 7 cm, maximum support depth - 12 cm;
- gas and foam concrete blocks- minimum 10-12 cm, optimal support depth - 15 cm;
- steel structures- 7 cm.
It is not recommended to support the floor slab more than 20 cm, because with an increase in the depth of support, it begins to “work” like a pinched beam. When laying floor panels on walls built from gas and foam concrete blocks, it is necessary to install a reinforced concrete armored belt, which is described in detail in the article:. Read also our article, which details,. We wish you to successfully apply the acquired knowledge on your construction sites!
Before starting the installation of the plates, it is recommended to seal the ends of the hollow holes. The voids are sealed so that water does not get inside the panel. It also increases the strength at the ends of the slabs (this applies to a greater extent to PC than to PB) in case of bearing partitions resting on them. The voids can be sealed by inserting a half brick into them and “throwing” the gap with a layer of concrete. Usually voids are sealed to a depth of at least 12-15 cm.
If water does get inside the plates, it must be removed. To do this, in the panel, in the "void", a hole is drilled from below through which water can flow out. This is especially important to do if the floors have already been laid, and the house went into the winter without a roof. Water in frost can freeze inside the hollow hole (because there is nowhere for it to flow out) and break the slab.
Sergey Perm FORUMHOUSE user
I had slabs laid on the ceiling for a whole year. I specially drilled holes in the "voids" with a perforator, a lot of water leaked out. Each channel must be drilled.
Before laying the floor slabs, it is necessary to select a truck crane of the required load capacity. It is important to take into account the accessibility of access roads, the maximum possible outreach of the crane and the permissible weight of the load. And also calculate the possibility of laying floor panels not from one point, but from two sides of the house.
zumpf FORUMHOUSE user
The surface on which the floor slab is laid must be flat and free of debris. Before laying the panel "spreads" cement mixture, so-called mortar "bed", 2 cm thick. This will ensure its reliable adhesion to the walls or armored belt. Also, before installing the panels and before applying the mortar to the wall, you can lay a reinforcing bar with a diameter of 10-12 mm.
A similar method will allow you to strictly control the verticality of mixing of all plates during their laying (since the panel will no longer fall below the rod). The rod will not allow her to completely squeeze out the cement mortar from under her and lie down “dry”. It is not allowed to put the plates "steps". Depending on the length of the plates, the divergence of the ends should not exceed 8-12 mm.
A serious mistake during laying is the overlapping of two spans with one slab at once, i.e. it rests on three walls. Because of this, loads unforeseen by the reinforcement scheme arise in it, and under certain, adverse circumstances, it may crack.
If such a layout cannot be avoided, to relieve tension, by upper surface panels, exactly above the middle partition (wall) is cut with a grinder.
Another point that should be focused on is how to block the flight of stairs between the floor slabs, if there is nothing to support them on. In this case, two channels can be run parallel to the plates, and one can be placed across, along the edge of the opening, tied reinforcing cage in the form of a grid with a cell of 20 cm and a rod diameter of 8 mm, etc. Place formwork and pour monolithic section. It is not necessary to tie the channel to the floor slabs. In this case, they rest on two short sides and are not subjected to loads from the support node of the flight of stairs.
How to properly store floor slabs on the site
Ideally, if the panels were brought to the site, they should be installed immediately. If for some reason this is not possible, the question arises: how to properly store them.
For storage of plates, it is necessary to prepare in advance a solid and flat area. You can't just lay them on the ground. In this case, the lower plate can rest on the ground, and, due to the uneven load, it will break under the weight of the upper plates.
Products should be stacked in a stack of no more than 8-10 pieces. Moreover, gaskets are placed under the bottom row (from a beam of 200x200 mm, etc.), and all subsequent rows are placed through gaskets - an inch board 25 mm thick. Gaskets should be located no further than 30-45 cm from the ends of the plates, and they should be set strictly vertically one above the other. This will ensure an even redistribution of the load.
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