What should be the minimum support of the floor slab on a brick wall in order to ensure the reliability and durability of the structure? The question is serious, the stability of the building to loads and the safety of people in it depends on its solution. That is why the depth of application of flat reinforced concrete products to brickwork is regulated by building regulations (SNiP).
The strength of the entire structure of the house depends on the quality of installation of floor slabs.
About hollow reinforced concrete products
It is difficult to understand the issue if you do not know what floor slabs are. These are structural elements of capital buildings, made of reinforced concrete, for the construction of floors between floors. Inside, along the entire slab, there are voids of various shapes, often round.
Products are manufactured according to standard designs - a series of drawings, where design features and dimensions are indicated. The length of the elements is 1.5-12 m. Modern production technologies allow cutting slabs of the required length with a step of 100 mm. The width of the product is made in 4 types: 1000, 1200, 1500 and 1800 mm.
The standard distributed load for which each element is designed is 800 kg / m 2. The slab can be 16-33 cm thick, depending on the design and length, the most common size is 22 cm.
Floor slabs are practically irreplaceable products. The alternative is either monolithic reinforced concrete. Wood loses to reinforced concrete in bearing capacity, and the construction of a monolithic structure is a complex and expensive process.
What determines the minimum distance for support
The normative documents set the minimum length of support of the end part of the hollow-core slab on the brick-built wall - 9 cm. A similar decision is made by design engineers with justification and calculations. Factors affecting the overlap depth:
The support parameters of the slab depend on the type of the future structure.- overall dimension of the span and length of the reinforced concrete product;
- the value of the distributed and point load on the concrete floor;
- types of loads - static, dynamic;
- the thickness of the bearing wall made of bricks;
- type of building - residential, administrative or industrial.
All of these factors must be taken into account in calculating the reliability of the structure. In accordance with the regulations, the end of the hollow-core reinforced concrete slab is applied to the wall so that the overlap size is 9-12 cm, accurate data are obtained by calculation.
If you study the series for which the elements of the floors are produced, then they indicate 2 types of sizes:
- Modular. This is the theoretical span where the element should be placed.
- Constructive. This is the net length of the ceiling slab from end to end.
The question arises - why the size of the support is so small, because the slab can be laid by 20-30 cm, if only the width of the fence allows it. But this will not be a support, but a pinching of a reinforced concrete element, since its end also carries part of the load from the wall built above. In such a situation, both the slab and the load-bearing partition will not work properly, which will lead to slow destruction and cracking of the brickwork.
And vice versa, due to too little overlap, the heavy slab, together with all the load, will begin to act on the edge of the masonry and eventually collapse it.
Therefore, the minimum support of 9 cm is rarely used in practice, usually 10-12 cm is taken.
There is one more reason why the edge of the slab should not be too deep inside the enclosing structure. The closer the end of the slab to the outer surface, the more heat is lost in such a structural unit, because concrete conducts heat well. The result will be a bridge of coldness, from which there will be cold floors in the house.
Support assembly design
During the construction of a brick building with floors made of flat concrete elements, the masonry in the full thickness of the fence is carried out to the design level of the bottom of the ceiling. Then the brick is laid only from the outside in such a way that a niche is formed where the slab will lie. The process is accompanied by the following:
- If the depth of support is 12 cm (exactly half a brick), then the niche is made at least 13 cm wide so that the end part of the slab does not rest on the brickwork.
- Before installing the floor, a layer of cement-sand mortar of the same grade that was used during the construction of the masonry is laid on the base.
- Since the edge zones of the slabs will perceive part of the load from the wall erected above, the voids from the end are tightly sealed with concrete inserts so that the product does not collapse from compression.
//www.youtube.com/watch?v\u003d-Ol8NGMGQGc
As a rule, concrete inserts are provided by manufacturers of reinforced concrete products at the factory. If this has not been done, the voids must be filled with concrete mixture of the M200 brand in the conditions of the construction site.
In the end walls of the building, the floor slabs lie on the outer fences not only with their ends, but also with one side part. Here, the bearing depth is not standardized, but for reliability, this unit should be designed in such a way that the load from the brickwork does not fall on the first void of the product. Otherwise, squeezing the hollow part may cause its destruction. The support shoulder should be minimal, its size depends on the slab design.
Building a house is fraught with many nuances that many novice builders do not even know about. In particular, one of these "pitfalls" is the floor assembly, 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 full responsibility, at least to become familiar with the consequences of neglect.
Acquaintance with floor nodes
The node supporting the floor slab on a brick wall is nothing more than a junction of two planes: vertical and horizontal. Many private developers play this moment in different ways, but this does not always work out correctly, and even more so reliably.
Therefore, to avoid the adverse consequences associated with costly repairs, it is necessary to prepare in advance.
Types of materials used for floors
By themselves, these floors are made of reinforced concrete slabs, the most reliable of the materials available.
But there are some differences in the production process, this is due to the type of structure:
- Aerated concrete.
- Prefabricated monolithic - the most popular of all.
- Made on the basis of heavy concrete... This type refers to many materials, since impurities of heavy concrete are present in various products.
- Hollow.
All of the above-described floors of brick buildings are used in certain conditions, depending on the construction plan, the load carried out and the dimensions of the span.
They should be divided into two categories:
- Interfloor ceilings in a brick house are used for multi-level houses. They are mounted in a load-bearing wall on a special lining, which ensures 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 an overlap made of precast concrete slabs. They have not only increased strength, but also a huge bearing capacity, as well as, if I may say so, affordable installation.
Supporting node - find a solution
To support the floor slabs on brick walls to withstand high loads, there is little use of durable materials, the most subtle approach is required here.
- At first, it is necessary to correctly calculate the bearing node. Keep in mind that it can only be implemented on a load-bearing wall, but cannot in any way be connected with a partition.
Note! Each product (building material) has its own marking, which indicates its specific 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 is not 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 refused construction.
For example, look at the marking of the PK 42.15-8T slabs, where PK is an overlap with round voids, 42.15 is the product dimensions in decimeters (length 4180, width 1490). The number 8 is the maximum permissible load on the slab, which is 800 kgf / m2, and the letter T following the 8 is the index of the heavy concrete used for the production of this slab.
There is also a certain standard of how the support of floor slabs on a brick wall should look like - from 90 to 120 mm. It is this size that should be maintained, adjusting to it.
There are two main points to keep in mind:
- 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.
- In no case should the width of the foundation be less than the brickwork. In this case, the deformation of the bearing walls is inevitable - the load of the floor will affect the bricks and weaken the cement mortar.
It is also necessary to focus on the thickness of the slab in relation to the thickness of the load-bearing wall. And this is provided that high-quality building bricks are used that comply with 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 thing to be aware of is that the location of the anchors is possible through the slab. However, there is also a limit - 3 meters from each other, this is a permissible maximum.
Note! The anchor is also used for fastening precast concrete slabs together.
Now you understand what is the node supporting the floor slab on the brick wall, what is connected with it and what it affects. That is why you can protect yourself from any unfavorable moments even 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 seam thickness, as the instructions say. All this can be done by yourself, but if in doubt, it is better to entrust the work to professionals.
The overlap is supported on aerated concrete by means of special armored belts. Its manufacture is necessary to receive loads from gravity and structural materials of the next floors or roof. What is an armopoyas? It is a monolithic reinforced concrete structure that follows the contours of the walls. Armopoyas is erected on load-bearing walls, which are built using aerated concrete.
For pouring the armored belt, formwork for concrete is prepared, which is a structure for creating a form in which reinforcement is laid for rigidity.
If the slabs are supported on the inner walls of the house, the walls are built in such a way that they rest on the foundation. The armopoyas on the inner walls under the floor slabs strengthens the structure, since the load is distributed over the entire area of \u200b\u200bthe slab. An armopoyas is not considered a structure made with brickwork on aerated concrete, as well as reinforcing aerated concrete masonry with a reinforced mesh.
To support floor slabs, the following requirements are imposed:
- floors and coverings should be installed on anti-seismic belts;
- the connection of plates and belts must be mechanically strong using welding;
- the belt should line up in the entire width of the wall; for external walls of 500 mm, its reduction by 100-150 mm is allowed;
- for laying the belt, it is necessary to use concrete with a class of at least B15.
Bearing depth
The support of the floor slab on the wall must be at least 120 mm, and the slab must be securely adhered to the load-bearing wall.
To fill the armopoyas, reinforcement is pre-installed, the number and location of which is determined by calculations. On average, at least 4 rods of 12 mm are accepted. If the aerated concrete will not be insulated, but only plastered, then the belt is not performed in the entire width of the wall, but less by the thickness of the insulation layer.
Armopoyas must be insulated, since it is a cold bridge. The formation of such a bridge can destroy aerated concrete due to the accumulation of moisture. Reducing the thickness of the armopoyas, do not forget about the minimum depth of support of the plates on the walls.
The depths of the support of the slabs on the walls have normalized values:
- when supported along the contour not less than 40 mm;
- when supported on two sides with a span of 4.2 m or less, not less than 50 mm;
- when supported on two sides with a span of more than 4.2 m, not less than 70 mm.
By keeping these distances, you can be sure that your home will not collapse.
The purpose of the armopoyas
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 the floor slabs on aerated concrete? Let's try to figure it out.
Firstly, the armopoyas increases the resistance of the structure of your house from deformation by loads of various kinds. For example, the shrinkage of the structure, the subsidence of the soil under it, temperature changes during the day and the change of season.
Aerated concrete cannot withstand high loads and deforms under the action of external applied forces. In order to prevent this from happening, armopoies are installed, which compensate for the loads. Armopoyas takes over the entire load, thereby preventing the destruction of the structure. Aerated concrete cannot withstand a point load, therefore, fastening wooden beams during roof construction becomes very difficult.
A way out of the situation is provided by an armopoyas. The second name of the armopoyas is unloading (due to its ability to evenly distribute the vertical load). Its use allows you to give rigidity to the structure. When steam and moisture move, aerated concrete as a porous material can expand, this can lead to movement of floor slabs.
Considering these factors, we can firmly say that an armored belt for supporting the floor slabs of the next floor or roof is simply necessary. Otherwise, for any level deviation, a point load is laid 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.
Making an armopoyas
Armopoyas 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 an armored belt, you need to prepare tools and accessories:
- hammer and nails for assembling the formwork with wood;
- reinforcement for assembling the frame;
- a welding machine for welding reinforcement rods in corners and at joints;
- container, bucket, spatula for pouring mortar into the formwork.
They are erected, moreover, under the floor slab, under the roof to facilitate the installation of the roof. If your house is supposed to build an attic, then for its slabs it is also necessary to increase the rigidity of the base.
For pouring the armopoyas, aerated concrete and formwork are prepared. Formwork is a structure for creating a form, which will later be filled with cement mortar. Formwork units:
- the deck that touches the concrete gives shape and quality to the face;
- forests;
- fasteners that keep the system stationary at the installation level and connect the individual elements to each other.
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 affordable formwork material is wood.
If you don't have time to prepare the formwork, you can spend money and rent it. Today there are many construction companies that provide such a service.
How to make formwork? The formwork design is not very complicated. Use boards 20 mm thick, 200 mm wide - these are the optimal dimensions. Too large a width can lead to the destruction of the formwork as a result of cracks. It is recommended to wet the boards before using. Shields of wooden formwork elements are tightly connected to each other. When doing this, avoid large gaps.
If the gap is up to 3 mm wide, you can get rid of it by wetting the boards abundantly. The material swells and the gap disappears. When the width of the gap in wooden elements is 3-10 mm, it is recommended to use tow, if the gap is more than 10 mm, then it is clogged with slats. The horizontality and verticality of the formwork is controlled using a 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 of wooden panels, you can wrap them with plastic wrap, this will also eliminate wide gaps.
The smoother the board used in the manufacture of wooden formwork, the more geometrically even the armored belt will be.
Reinforcement is placed in the formwork. The ideal option is to use four rods with a diameter of 12 mm or a ready-made reinforcing cage. The minimum requirements are the laying of two 12 mm rods. Reinforcement rods are connected by a "ladder" with a pitch 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 volumetric frame structure is used. In order for the fabricated frame not to touch the aerated concrete blocks, it is laid on pieces of bricks or blocks. Before pouring the solution, the position of the frame is checked by level. Having prepared the solution, the armopoyas is poured. For the solution, use 3 buckets of sand, 1 bucket of cement and 5 buckets of rubble. For the convenience of work, small crushed stone is used.
If the installation of the armopoyas is planned in stages, then the pouring is carried out according to the principle of vertical cutting. That is, the frame is poured completely along the height to a certain place, then the jumpers are set. The material for the lintels can be a brick or a gas block.
The work is suspended. Before carrying out further work, the material of the lintels is removed, the solidified, filled part is well moistened with water, as this provides a better abutment. Pouring of concrete should be carried out without the formation of voids; for this, the surface is leveled with reinforcement.
After 3-4 days, the formwork can be dismantled.
On the received armopoyas. In practice, hollow-core slabs made of heavy concrete, aerated concrete, precast-monolithic are used. They are selected based on the size of the span and the bearing capacity.
Most often, hollow-core slabs PC and PNO are used, the bearing capacity of which is 800 kgf / m2. The advantages of such floor slabs include high strength, manufacturability and full factory readiness for installation.
The support of the floor slab on the armored belt of the aerated block structure should be 250 mm. Typical support is 120 mm.
Armopoyas in the 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 overlap hangs over the void. To support the slab, columns are erected with lintels in the form of beams.
Pillars can be erected using bricks, blocks. Each pillar is laid out in one and a half bricks.
Reinforced concrete lintels are being erected between the posts. The height of the beams should be 1/20 of the opening length. 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 heights from the ratio of 0.1 m \u003d 5/7. If the distance between the supports is 2 m, and the height of the beams is 0.1 m, then the width of the reinforced concrete beams is 0.07 m. For pouring the beams, a removable plank formwork is used.
Reliability of floor support on load-bearing walls ensures safe, reliable and long-term operation of the entire building. The constructive stability of engineering structures depends on competent execution. Therefore, the support of floor slabs on the walls is regulated by SNiP.
Parameters that determined the amount of support
The depth of the overlap on the walls depends on the following factors:
- purpose and type of buildings - residential, administrative, industrial;
- material and thickness of load-bearing walls;
- the size of the span to be covered;
- dimensions of reinforced concrete structures and their own weight;
- the type of loads acting on the floor (static or dynamic), which of them are permanent and which are temporary;
- values \u200b\u200bof point and distributed loads;
- seismicity of the construction area.
All the factors listed above are necessarily taken into account when performing calculations of the reliability of the construct. In accordance with the current regulatory documents, the support of the floor slab on the brick wall is taken from 9 to 12 cm, the final size is determined by engineering calculations during the design of the building. With less overlaps, the heavy dead weight of the elements, together with the existing loads, will have a direct effect on the edge of the masonry, which can lead to its gradual destruction.
On the other hand, a larger overlap will already be a kind of pinching of reinforced concrete elements with the transfer of weight from the upper section of the wall to their ends. The result is cracking and slow destruction of the wall masonry. Also, when the ends of the products approach the outer surfaces of the walls, an increase in heat loss in reinforced concrete elements occurs with the formation of cold bridges, leading to the formation of cold floors. The cost of parts is proportional to their length, so excessive pinching will increase the cost of the structure.
Node for supporting the floor slab on a brick wall
When erecting brick buildings with precast concrete slabs, the laying is carried out in full thickness to the design bottom of the ceilings. Further, the bricks are laid only on the outside of the walls to form a niche into which the slabs can be laid.
It is important to observe the following conditions in the support nodes:
- the ends should not rest against the brickwork, so for the overlap most often used in practice of 12 cm, the width of the niche is ≥ 13 cm;
- the mortar on which the slabs are laid is of the same brand as the masonry;
- the voids in the channels are sealed from the ends using concrete liners, which will protect the ends from destruction when squeezed under loads. The production of concrete liners is carried out in factories with delivery upon purchase of slabs; in the absence of liners, the channel voids are filled with B15 concrete directly at the construction site.
On the end brick walls, slab reinforced concrete products also fall on one side. In this case, the minimum support of the floor slab on the end walls is not standardized. But in order to avoid the destruction of the product when the hollow channel is squeezed, the installation should be carried out so that the masonry laid out above the ceiling does not lie on the extreme void of the structure and the shoulders of the moments acting from the load should be of minimum values.
Requirements for the device of armored belts for floor slabs
In buildings with walls made of blocks made of lightweight concrete (aerated concrete, aerated concrete, aerated concrete, polystyrene concrete), which have low strength characteristics, the overlap must necessarily rely on reinforced belts. Armopoyas is arranged around the entire perimeter of the building. The height of the armored belt under the floor slabs is from 20 to 40 cm. The connection of the reinforced belts with the floor details must be mechanically strong, for which anchoring devices are used or joining with reinforcing bars of a periodic profile using electric welding.
A number of the following requirements are imposed on the design:
- belts should fit the entire width of the walls; for external widths ≥ 50 cm, a decrease of ≤ 15 cm is permissible for laying insulation;
- reinforcement, made using engineering calculations, must provide sufficient mechanical strength to take the loads from the dead weight of reinforced concrete elements and upstream structures;
- concrete ≥ class B15;
- the belt is a kind of cold bridge, therefore, its mandatory insulation is necessary in order to prevent the destruction of aerated concrete blocks from accumulated moisture;
- reliability of adhesion to load-bearing walls.
The support of the floor slabs on the aerated concrete blocks of the bearing walls along the reinforced belts is carried out in compliance with the following standardized values:
- at the ends ≥ 250 mm;
- along the rest of the contour ≥ 40 mm;
- when supported on the 2 sides of the span ≤ 4.2 m - ≥ 50 mm;
- the same with a span ≥ 4.2 m - 70 mm.
Aerated concrete blocks are not able to withstand high loads, the material begins to undergo various deformations. Armopoyas, taking on all the loads, evenly distributes them, thereby ensuring that the structure is not destroyed.
Installation of floor slabs on gas silicate blocks is also performed with the obligatory installation of monolithic reinforced concrete belts. The required support values \u200b\u200bcorrespond to the values \u200b\u200bgiven above for walls made of aerated concrete blocks.
During the installation work, the following conditions must be met:
- compliance with the symmetry of the laying of elements in the spans;
- the ends of the slabs must be aligned in one line;
- all elements must be located in the same horizontal level (control is carried out using a building level), the permissible deviation in the plane of the plates is ≤ 5 mm;
- mortar thickness under the boards ≤ 20 mm, the mortar must be freshly prepared, without starting the setting process. Additional dilution of the mixture with water is inadmissible.
It is unacceptable to lay rows of bricks or reinforcing meshes instead of an armored belt.
Reinforced concrete slabs are one of the most common types of floors. They provide high strength and allow you to mount a rigid structure in the shortest possible time. Installation of floor slabs is a demanding task that requires certain knowledge in the field of construction. Everything in order.
Floor slab types
Before starting to mount the horizontal structure, you must select the type. Reinforced concrete prefabricated structures are produced in the form:
- hollow;
- flat (PT);
- hip panels with perimeter ribs;
- with longitudinal ribs.
Most often, the use of reinforced concrete hollow-core... They are available in two types, depending on the manufacturing method:
- round-hollow (PC);
- continuous molding (PB).
Hollow core slabs are time-tested products that have been used in construction for several decades. Many regulations and installation rules have been developed for them. Thickness - 220 mm. Products are installed according to serial dimensions, which creates inconvenience for individual construction.
The manufacturing technology of these slabs implies the use of reusable casting molds, and before the manufacture of atypical products, you first need to prepare the formwork. Therefore, the cost of the required size can increase significantly.... Typical PC slabs have a length of 2.7 to 9 meters in 0.3 m increments.
Scheme of reinforced concrete products with dimensions The width of reinforced concrete products can be:
- 1.0 m;
- 1.2 m;
- 1.5 m;
- 1.8 m.
Structures with a width of 1.8 m are extremely rarely purchased, since, due to the large weight, the process of installation in the design position is greatly complicated.
PB are used in much the same way as the previous type. But the technology of their manufacture allows giving the product any length. Thickness - 220 mm. Width as PC series. The disadvantage is the little experience of use and the raw regulatory documentation.
Flat PTs are often purchased as additional elements for hollow-core slabs. They are produced with a thickness of 80 or 120 mm and are smaller in size, allowing to block narrow corridors, closets, and bathrooms.
Supporting plates
The laying of floor slabs is carried out after the preparation of the project or the scheme on which the products are laid out. Floor elements must be selected so that they are sufficiently supported on a brick wall or expanded clay concrete blocks and laid without gaps in width.
The minimum support for the PB and PC series depends on their length:
- products up to 4 m long - 70 mm;
- products longer than 4 m - 90 mm.
A visual diagram of how and how to correctly support floor slabs Most often, designers and constructors take the optimal value of support on the wall 120 mm. This value guarantees reliability with small deviations during installation.
It will be correct to pre-position the bearing walls of the house at such a distance that it is easy to lay the slabs. The distance between the walls is calculated as follows: length of standard slabs minus 240 mm. Series PK and PB must be supported on two short sides without intermediate supports. For example, PK 45.15 has a size of 4.48 m, 24 cm is subtracted from it. It turns out that the distance between the walls should be 4.24 m. In this case, the products will lie with the optimal amount of support.
The minimum support for the PT series products on the wall is 80 cm. Installation of such reinforced concrete slabs is possible with the location of support points on all sides.
The support should not interfere with the passage of ventilation ducts. The optimum thickness of the internal bearing brick wall is 380 mm. 120 mm on each side goes under the reinforced concrete ceiling, and 140 mm remains in the middle - the standard width of the ventilation duct. In this case, it is necessary to lay as correctly as possible. Displacement of the product towards the ventilation opening will lead to a decrease in its section and insufficient ventilation of the premises.
Summarizing what was said:
- series PC and PB up to 4 m are supported on both sides by at least 7 cm;
- series PC and PB more than 4 m - not less than 9 cm;
- pT series - on two, three or four sides at least 8 cm.
Storage of boards
Warehousing schemes for products of different types After the scheme has been developed and the products have been purchased, they need to be located on the building site for convenient installation in the design position. There are rules for storing materials:
- elements need to be laid under a canopy;
- the storage place should be located in the access zone of the crane;
- lining is provided for the support points.
Failure to follow the last rule will lead to a split in half. PC, PB and PT products work in such a way that the appearance of intermediate supports or a solid base leads to cracks. Laying is performed in the following order:
- wooden blocks or boards are laid on the ground under the edges of the slab;
- on the boards with a crane from the machine I shift the floor element;
- boards or bars are again placed on the laid plate;
- unload the second plate from the machine;
- repeat points 3 and 4, the maximum storage height is 2.5 m.
Masonry requirements
Floor slab calculation scheme In order to properly install floor slabs, it is necessary to ensure that special requirements for a brick wall are met:
- evenness of the masonry in the place of laying the floors;
- laying in three rows to overlap reinforcing meshes with a mesh of 5 by 5 cm from wire with a diameter of 3-4 mm;
- the top row of masonry from the inside should be butted.
If the slabs are mounted on expanded clay concrete blocks, a monolithic belt is additionally arranged under the floors. Such a design will help to evenly distribute the load from heavy floors on expanded clay concrete blocks with less strength. Construction technology provides for pouring a monolithic tape of concrete 15-20 cm thick onto blocks.
Floor laying
To carry out the work, at least three people will be required: one performs slinging, and two install them in the design position. If the installers and the crane operator cannot see each other, when installing the slab, another worker will be needed to give commands to the crane.
Reinforced concrete product laying scheme Fastening to the crane hook is performed with a four-branch sling, the branches of which are fixed at the corners of the slab. Two people stand on both sides of the support and control its evenness.
When installing a PC, pinching into the wall is carried out in a rigid way, that is, bricks or blocks are laid both above and below the slab. When using slabs according to the PB series, it is recommended to perform hinged fastening. For this, the plates are not pinched from above. Many builders mount the PB series in the same way as PCs and buildings stand, but it's not worth the risk, because human life and health depend on the quality of the installation of supporting structures.
Another important feature of the use of products from the PB series is that it is prohibited to make technological holes in them.
These punches are needed for heating pipes, water supply and sewerage. Again, many builders neglect this even when building multi-storey buildings. The difficulty is that the behavior of this type of floor under load over time has not been fully studied, since there are no objects built long ago. The ban on punching holes has reasons, but it is rather preventive.
Slab cutting
Sometimes, to install a slab, you need to cut it. The technology provides for work with a grinder with a disc on concrete. It is impossible to cut the PC and PT slabs along the length, since they have reinforced reinforcement in the support zones. If you support such a cut slab, then one edge will be weakened, serious cracks will go along it. It is possible to cut PB slabs in length, this is due to the peculiarities of the manufacturing method. A bar or board is laid under the cut site, which will facilitate the work.
The division along the length is performed along the weakened part of the section - the hole. This method is suitable for PCs, but not recommended for PBs, since the width of the walls between the holes is too small.
After installation, the holes in the areas of bearing on the walls are poured with lightweight concrete or clogged with mineral wool. This is necessary to provide additional strength in the pinch points in the walls.
What to do if it was not possible to evenly spread the product across the width
Sometimes the dimensions of the room do not correspond to the width of the products, in this case all the gaps are brought together into one. This space is covered with a monolithic section. Reinforcement takes place with curved meshes. In length, they lean on the top of the floor and seem to sag in the middle of the monolithic section. for floors, concrete is used at least B 25.
The precast floor technology for bricks or blocks is quite simple, but requires attention to detail.