Supporting hollow-core floor slabs on a brick wall. Supporting the floor slab on the wall
Building a house is a very difficult process, which is fraught with a sufficient number of pitfalls. These include support units for floor slabs. This installation technology, on which the strength and service life of the house depends. In such mates, the horizontal and vertical planes are joined to each other.
It happens that when building a private house, it is not possible to make the joint of building elements efficiently. This, in turn, dictates in the foreseeable future the incurrence of costs for very expensive repairs or serious destruction of structures.
TYPE OF MATERIAL FOR COLORS
Today, most of them are made of reinforced concrete. This circumstance is dictated by the fact that reinforced concrete is an extremely durable material, and its reliability has been tested not only by calculations, but also by time. The structure of the floors varies. Meet:
- plates with cells;
- prefabricated monolithic structures;
- monoliths made of heavy concrete;
- multi-hollow slabs.
The nature of the conditions for the use of slabs can be very different and depends on a number of factors: the dimensions of the building, the magnitude of the load, etc.
Floors in brick house are divided into the following types:
- Floors between floors.
- Attic floors.
The first type is used for houses that are characterized by a multi-level structure. Support plate brick wall lies on a special lining. This ensures that the product is securely fixed. What is important is the depth to which the slab rests on the wall.
If there is an attic type, then significant loads are not observed, and there is no need for lining.
A special feature of such ceilings is that they insulate from unwanted noise and save heat. It is necessary to use heat insulators not only from the attic side, but also at the junctions of the walls and the ceiling.
SEARCHING FOR SOLUTIONS FOR THE SUPPORT UNIT
The support unit must withstand significant loads. It is not enough that materials with a safety margin are used in construction; additional measures must also be taken.
1. It is necessary to carry out the correct calculation of the support unit. It should be borne in mind that such calculations can only be carried out in relation to load-bearing structures, but not partitions.
2. To determine minimal support floor slabs on a brick wall, all calculations must be checked against GOST 956-91 and the building design.
Each plate has its own marking. In the document, for each brand there is a figure characterizing the maximum load on the slab. There is a standard that characterizes the amount of support of slabs on a wall with brickwork. It ranges from 90 to 120 mm. These parameters should be adjusted to.
This indicator is important both at the construction and design stages.
Iron concrete floor, consisting of slabs, can be classified as a load-bearing element of the building. Divided by plates interior space multi-story building into floors, and basements are separated, as well as attic spaces. Each slab receives the load from the equipment, people, and furniture located on it and transfers it, including its weight, evenly to the walls.
In specialized construction literature, a definition of the standard is given - what should be the minimum unlocking of a floor slab on a brick wall. This indicator is defined as 100 - 150 mm. For example, for a hollow slab 6 m long, the expected support on the brick should be at least 100 mm.
To more accurately determine the slab support area, additional specific calculations should be made. They should take into account the length of the slab, the material of manufacture, its total weight, and also decide what the expected load will be on it. These calculations should also take into account the thickness of the brick wall to support the slab.
Building a house is fraught with many nuances that many novice builders don’t even know about. In particular, one of these “pitfalls” is the floor assembly, which is an entire technology responsible for the durability of the house.
That is why it is necessary to approach the solution of this problem with all responsibility, and at least become familiar with the consequences of negligence.
Introduction to floor assemblies
The assembly of supporting a floor slab on a brick wall is nothing more than the junction of two planes: vertical and horizontal. Many private developers play with this point in different ways, but it doesn’t always work out correctly, much less reliably.
Therefore, to avoid adverse consequences associated with expensive repairs, it is necessary to prepare in advance.
Types of floor materials used
These floors themselves are made from reinforced concrete slabs, the most reliable materials available.
There are just some differences in production process, this is related to the structure type:
- Cellular concrete.
- Prefabricated monolithic– the most popular of all presented.
- Made from heavy concrete. This type applies to many materials, since admixtures of heavy concrete are present in various products.
- Multi-hollow.
All of the above floors brick buildings used in certain conditions, depend on the design of the structure, the load being carried out and the dimensions of the span.
They should be divided into two categories:
- Interfloor ceilings in a brick house - used for multi-level houses. They are mounted into a load-bearing wall on a special lining, which ensures reliable fixation of the product. In this case, the depth from which the ceiling will lie on the wall is very important.
- The attic type does not experience such high loads, so it is mounted into the wall without a lining.
For your information! If you decide to build a multi-story brick house with your own hands, you should give your preference to a floor made of prefabricated reinforced concrete slabs. They have not only increased strength, but also enormous load-bearing capacity, and also, so to speak, affordable installation.
Support node - find a solution
In order for the support of floor slabs on brick walls to withstand high loads, little use durable materials, this requires the most subtle approach.
- Firstly, you need to correctly calculate the support unit. Keep in mind that it can only be implemented on a load-bearing wall, but cannot be connected in any way to a partition.
Note! Each product ( building 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 sand-lime brick M 150 – not the best best solution for the construction of a multi-storey building.
- Secondly, all calculations and a plan for solving the problem must be checked against GOST 956-91 and additional design documents. Otherwise, you may be denied construction.
For example, check out the markings of PC 42.15-8T slabs, where PC is the floor with round voids, 42.15 is the dimensions of the product in decimeters (length 4180, width 1490). Number 8 – maximum permissible load per slab, which is equal to 800 kgf/m2, and the letter T following 8 is the index of the heavy concrete used for the production of this slab.
There is also a certain standard for how the support of floor slabs on a brick wall should look - from 90 to 120 mm. It is this size that should be maintained, adapting 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, resulting in curvature of the ceiling.
- The width of the foundation should in no case be less than the brickwork. In this case, the deformation load-bearing walls is inevitable - the load of the ceiling will affect the bricks and weaken the cement mortar.
You also need 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 brick, which complies 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 It is extremely difficult to do on your own, so it is better to entrust it to professionals, although the price may be unpleasantly high. The main thing in the construction business is reliability and durability.
One feature to be aware of is that the anchors can be positioned through the slab. However, there is a limit - 3 meters from each other, this is the permissible maximum.
For your information! The anchor is also used to fasten prefabricated reinforced concrete slabs together.
Now you understand what a unit 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 unfavorable moments even at the design stage.
Conclusion
It is important not only to lay the slabs correctly, but also to build a foundation, withstand the drying time of the mortar, and lay bricks with minimum thickness seam according to the instructions. You can do all this yourself, but if you are in doubt, it is better to entrust the work to professionals.
Floor slabs
Factory-made floor slabs are a very popular option for floors in individual housing construction, because... the alternative is a monolithic concrete floor - a much more labor-intensive thing, difficult for inexperienced private developers. Unlike a monolith, slabs come with a factory-guaranteed maximum load, which is more than enough in a private home.
Description
There are two GOST standards for floor slabs in Russia:- GOST 9561-91 “Reinforced concrete hollow-core floor slabs for buildings and structures. Technical conditions."
- GOST 26434-85 “Reinforced concrete floor slabs for residential buildings. Types and basic parameters."
- 1PK - 220 mm thick with round voids with a diameter of 159 mm, designed for support on two sides;
- 1PKT - the same, for support on three sides;
- 1PKK - the same, for support on four sides;
- 2PK - 220 mm thick with round voids with a diameter of 140 mm, designed for support on two sides;
- 2PKT - the same, for support on three sides;
- 2PKK - the same, for support on four sides;
- 3PK - 220 mm thick with round voids with a diameter of 127 mm, designed for support on two sides;
- 3PKT - the same, for support on three sides;
- 3PKK - the same, for support on four sides;
- 4PK - 260 mm thick with round voids with a diameter of 159 mm and cutouts in the upper zone along the contour, intended for support on both sides;
- 5PK - 260 mm thick with round voids with a diameter of 180 mm, designed for support on two sides;
- 6PK - 300 mm thick with round voids with a diameter of 203 mm, designed for support on two sides;
- 7PK - 160 mm thick with round voids with a diameter of 114 mm, designed for support on two sides;
- PG - 260 mm thick with pear-shaped voids, designed for support on two sides;
- PB - 220 mm thick, manufactured by continuous molding on long stands and designed to be supported on two sides.
This list does not include PNO type floor slabs, which are found in reinforced concrete manufacturers. In general, as far as I understand, slab manufacturers are not required to comply with GOST (Government Decree No. 982 of December 1, 2009), although many produce and label slabs in accordance with GOST.
Manufacturers produce slabs different sizes, you can almost always find the size you need.
Floor slabs in most cases are made prestressed (clause 1.2.7 of GOST 9561-91). Those. The reinforcement in the slabs is tensioned (thermally or mechanically), and after the concrete has hardened, it is released back. The compression forces are transferred to the concrete, and the slab becomes stronger.
Manufacturers can strengthen the ends of the slabs that are involved in the support: fill round voids with concrete or narrow them in this place cross section voids. If they are not filled by the manufacturer and the house turns out to be heavy (the load on the walls at the ends increases accordingly), then the voids in the area of the ends can be filled with concrete yourself.
The slabs usually have special hinges on the outside, by which they are lifted by a crane. Sometimes reinforcement loops are located inside the slab in open cavities located closer to the four corners.
Floor slabs in accordance with paragraph 1.2.13 of GOST 9561-91 are designated as: type of slab - length and width in decimeters - design load on the slab in kilopascals (kilogram-force per square meter). The reinforcement steel class and other characteristics may also be indicated.
Manufacturers do not bother with designating the types of slabs and in price lists they usually write only the type of slab PC or PB (without any 1PK, 2PK, etc.). For example, the designation “PK 54-15-8” means a 1PK slab with a length of 5.4 m and a width of 1.5 m and with a maximum permissible distributed load of approximately 800 kg/m 2 (8 kilopascals = 815.77 kilogram-force/m 2 ).
Floor slabs have a bottom (ceiling) and top (floor) side.
According to paragraph 4.3 of GOST 9561-91, slabs can be stored in a stack with a height of no more than 2.5 m. Pads for the bottom row of slabs and spacers between them in a stack should be located near the mounting loops.
Supporting the slabs
Floor slabs have a support zone. According to paragraph 6.16 of the “Manual for the design of residential buildings Vol. 3 (to SNiP 2.08.01-85)":The depth of support of prefabricated slabs on walls, depending on the nature of their support, is recommended to be no less than, mm: when supported along the contour, as well as two long and one short sides - 40; when supported on two sides and the span of slabs is 4.2 m or less, as well as on two short and one long sides - 50; when supported on two sides and the span of the slabs is more than 4.2 m - 70.
The slabs also have a series of working drawings, for example, “series 1.241-1, issue 22”. These series also indicate the minimum support depth (it may vary). All in all, minimum depth The support of the slab must be checked with the manufacturer.
But there are questions regarding the maximum depth of support for the slabs. IN different sources given completely different meanings, somewhere it is written that 16 cm, somewhere 22 or 25. One friend on Youtube assures that the maximum is 30 cm. Psychologically, it seems to a person that the deeper the slab is pushed into the wall, the more reliable it will be. However, there is definitely a limitation on the maximum depth, because if the slab goes too deep into the wall, then bending loads “work” differently for it. The deeper the slab goes into the wall, the lower the permissible stresses from loads on the supporting ends of the slab usually become. Therefore the value maximum support It’s also better to check with the manufacturer.
Similarly, slabs cannot be supported outside of the support zones. Example: on one side the slab lies correctly, and on the other side it hangs, resting on the middle load-bearing wall. Below I have drawn it:
If the wall is built from “weak” wall materials like aerated concrete or foam concrete, then you will need to build an armored belt to remove the load from the edge of the wall and distribute it over the entire area of the wall blocks. For warm ceramics, an armored belt is also desirable, although instead of it you can lay several rows of ordinary durable solid brick, which does not have similar problems with support. With the help of an armored belt, you can also ensure that the slabs together form a flat plane, so there is no need for expensive ceiling plaster.
Laying slabs
The slabs are placed on the wall/armoured belt on cement-sand mortar 1-2 cm thick, no more. Quote from SP 70.13330.2012 (updated edition of SNiP 3.03.01-87) “Load-bearing and enclosing structures”, paragraph 6.4.4:Floor slabs must be laid on a layer of mortar no more than 20 mm thick, aligning the surfaces of adjacent slabs along the seam on the ceiling side.
Those. the slabs are leveled to create a level ceiling, and an uneven floor can then be leveled with a screed.
During installation, the slabs are placed only on those sides that are intended for support. In most cases, these are only two sides (for PB and 1PK slabs), so you cannot “pinch” the third side, which is not intended for support, with the wall. Otherwise, the slab clamped on the third side will not correctly absorb the loads from above, and cracks may form.
Laying of floor slabs must be done before construction interior partitions, the slabs should not initially rest on them. Those. first you need to let the slab “sag”, and only then build non-load-bearing interior walls (partitions).
The gap between the plates (the distance between the sides) may vary. They can be laid closely, or with a gap of 1-5 cm. The gap space between the floor slabs is then sealed with mortar. Usually the gap width is obtained “by itself” when calculating required quantity slabs, their size and distance to be covered.
After installation, floor slabs can be tied together using, for example, welding. This is done in earthquake-prone regions (Ekaterinburg, Sochi, etc.); in ordinary regions this is not necessary.
In places where it is difficult to select a floor slab or where it is impossible to install it correctly, a monolithic floor should be poured. It must be poured after installing the factory slabs in order to correctly set the thickness of the monolith. You need to make sure the installation is tight monolithic ceiling, especially if a ladder will rest on it. The space formed between floor slabs does not always have a trapezoidal shape or a shape with slab protrusions on which you can rest. If the monolith turns out to be rectangular and is not supported by the beveled edges of the adjacent slabs, then it can simply fall out.
Insulation
The ends of floor slabs lying on external walls must be insulated, because reinforced concrete has high thermal conductivity and the slab in this place becomes a cold bridge. Extruded polystyrene foam can be used as insulation. I drew an example:
To carrier outer wall 50 cm thick includes a slab with a support of 12 cm, which is insulated at the end with EPS ( orange) 5 cm thick.
When designing, and especially implementing a house, that is, construction, there are many nuances that generally affect the strength of the entire structure. Floor assemblies were no exception, because they are entirely responsible for exactly what load the laid structures will withstand.
Between the end of the wooden floor beam and brick wall you need to make a ventilated air gap.
So, let's look at what the nodes of these systems are and how they are mounted.
Some characteristics
The floors themselves are usually made of reinforced concrete slabs, which are produced in a special way in a factory.
According to the type of material from which they are made, they can be divided into:
- cellular concrete;
- multi-hollow;
- made of heavy concrete;
- as well as prefabricated monolithic structures.
In each case of construction, the floor material is selected individually, in connection with the tasks assigned to the planned device, as well as the span width, etc.
Based on their design, similar products can be divided into:
- interfloor;
- attics.
Scheme of embedding the ceiling into the outer wall: 1 - wall; 2 - lining; 3 - end of the beam to be sealed; 4 - floor slab.
In brick houses with more than two floors, it is planned to use precast reinforced concrete floors. The indisputable advantage of such reinforced concrete structures is their enormous strength and load-bearing capacity. When using reinforced concrete elements, you can safely create a basement.
Interfloor systems located on different heights, may have small design features related to the need for heat or sound insulation. For example, if the element is located between an unheated attic and a living space or between a basement and the first floor of a residential building.
The ceilings separating the attic from the living quarters do not bear heavy loads during operation, which means their design is lightweight.
During installation, reinforced concrete slabs must be laid tightly to each other, and the seams must be filled cement mortar.
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Features of these systems
In order for the ceiling to hold tightly and be able to withstand large and even excessive loads, it is necessary to correctly calculate the node for supporting the floor slab on the brick wall. Depending on how it is implemented, it will be possible to place a certain load on a given floor of the building. By the way, please note: a slab support unit cannot be constructed based on lintels rather than load-bearing walls.
Scheme for embedding a wooden floor beam into a brick wall: 1 - wooden beam; 2 - the end of the beam, coated with resin and wrapped in roofing felt;
3 - waterproofing; 4 - brick wall; 5 - air gap between the wall and the beveled end of the beam.
In construction, as in any industry, there are special regulatory documents governing the standards for installing support units on various walls, including brick ones.
In order to accurately determine the “depth of support”, it is necessary not only to take into account the immediate length of the selected slab, but also the material itself on which this slab will rest. Therefore, all products, as a rule, are marked, that is, they indicate the maximum load-bearing capacity, as well as the level of minimum seismic resistance.
Construction control authorities carefully monitor exactly how these structures are laid and what is the supporting area of the load-bearing wall of the building.
This is of great importance, since an incorrectly installed unit on a brick wall will be a violation that will lead to a ban on construction or reworking a completely already constructed part of the building.
At the same time, regulatory authorities are guided by modern, existing at the moment GOSTs, as well as a series project documentation, where the amount of support is precisely indicated. In accordance with the existing GOST 956-91, which regulates the depth of support of a ceiling of any length on a load-bearing brick wall, this value is 10 mm, excluding the length of the device itself. Therefore, when choosing a reinforced concrete slab for an organization, it is necessary to carefully study the markings applied to it, as it will give all the necessary information about this reinforced concrete product.
As a rule, slab markings consist of a group of letters and numbers. For example, PC slab 42.15-8T. The letters PC are the name of the product itself, in this case it is a floor slab with round voids; numbers 42.15 indicate the dimensions of reinforced concrete products in decimeters (structural length is 4180, and width is 1490); the number 8 means maximum load for this slab - 800 kgf/sq.m; the letter T is an index for the heavy concrete used in the manufacture of the slab.
When carrying out construction activities for the construction of buildings, for the installation interfloor ceilings Hollow and ribbed panels are used. They are reinforced with steel reinforcement, which allows them to compensate for the resulting stresses. To ensure the strength of the buildings being erected, it is necessary to correctly support the floor slabs on the load-bearing walls. It is important to correctly position the interfloor panels and provide the required supporting surface area. Compliance with these requirements will improve the reliability of constructed structures and their service life.
Features and purpose of floor panels
Structural elements of a building that vertically divide space into functional zones are called floors. They take the weight of structures, equipment, furniture, people and transmit forces to main walls, supporting elements and crossbars. Made from reinforced slabs required sizes.
Located in different areas:
- above the basement;
- between floors of a building;
- under the attic space.
Floors are formed from reinforced concrete or cellular concrete and classified as follows:
- prefabricated monolithic. They consist of a group of elements, the gaps between which are concreted;
- prefabricated They are formed by continuously laying solid and hollow elements on permanent supports.
Features of the panels are:
- increased strength;
- increased load-bearing capacity;
- installation readiness;
- manufacturability.
Floors formed from correctly installed slabs are characterized by the following properties:
- reliability;
- rigidity;
- moisture resistance;
- fire resistance;
- soundproof;
- durability.
Slabs with round or oval-shaped voids are used when the distance between main walls is no more than 9 m; they are supported, as a rule, by two sides, providing increased spatial rigidity of the structures being built.
Supporting walls intended for installation of overlapping elements can be made of the following materials:
- various types bricks;
- foam blocks;
- aerated concrete elements;
- reinforced concrete.
To ensure the stability of erected buildings, one of the most important parameters, which determine spatial rigidity, is the depth of support of the floor slabs on the brick wall, as well as capital supports made of other types of building materials.
How to properly support a floor slab on load-bearing walls
It is important to know how to install overlap panels. There are two options:
- on two opposite sides. Short sections are mounted on two supports, reinforcement cage compensates for bending stresses. At the same time, the product is evenly deformed under the influence of loads, maintaining its integrity thanks to the reinforcement frame;
- on three supports forming a solid contour. The method is used when placing the slabs along the edges of the room with the long side resting on the wall. When installing, it is important to support the long side at a distance not exceeding the height of the product. Reinforced structure it bends not with the entire plane, but with the free edge.
It is prohibited to install as follows:
- leaning on the walls with long sides. The formation of cracks and damage to integrity is possible, since the reinforcement cage compensates for stress only in the longitudinal direction;
- on three sequentially located supports. There is a high probability of the central zone of the slab bending in the opposite direction with the formation of a stretched section in the upper part. A single-span structure may crack;
- on two supports with a cantilever overhang of the outer part of the panel. Inexperienced developers use this option to construct a balcony, but as the console increases, there is a risk of structural destruction;
- to separately located ends of the columns. This method contradicts the principle of operation of fittings, which cannot ensure the integrity of the product and perform the assigned functions in such conditions;
- with one-sided or two-sided pinching of the extreme areas. Clamped panels differ in operating principle from elements with hinged support. Pinching can cause unwanted cracks to form.
When planning the installation of ceiling panels, it is important to choose correct method installation and avoid mistakes.
Depth of support of floor slabs on various types of walls
Active regulatory documents And building regulations The following dimensions of the supporting surface for walls made of various materials are regulated:
- large-panel structures – 5–9 cm;
- brick supports - 9–12 cm;
- aerated concrete walls - 12 cm;
- foam block elements – 12 cm;
- external, main walls - up to 25 cm.
Supporting floor slabs on walls - design parameters
When constructing buildings they are used various slabs ceilings The minimum support depends on a number of factors:
- product length;
- masses of the span structure;
- thickness of the main wall;
- presence of thermal insulation and cladding;
- seismic resistance of the building;
- type of acting loads.
When performing calculations, it is important to consider how long the load will last and whether it is permanent or temporary. These types of calculations are quite complex. They are carried out by specialists from design organizations. When developing a project and performing installation activities, an individual developer must take into account the tabular values obtained by calculation.
Supporting hollow core slabs during installation
To perform panel installation work, you must prepare special equipment and tools:
- a truck crane, the lifting capacity of which allows you to lift the slabs;
- rigging equipment - slings corresponding to the weight of the panels and a mooring cord;
- inventory scaffolding, facilitating the performance of work at height;
- mounting crowbar, which allows you to adjust the position of the slabs during installation;
- plumb line and level necessary to control the location of the panels;
- anchors that fix the slabs after they are installed on the supporting surface of the walls.
To seal the gaps, you will also need a cement mortar, which must be prepared before installation.
When installing elements in brick buildings, observe the dimensions of the supporting surface. Carry out work according to the following algorithm:
- Check the horizontality of the supporting surface of the brick walls on which the support beams are to be installed. The height difference should not exceed 1 cm.
- Place pre-prepared cement mortar over the entire area of the supporting surface. Level the surface in the contact area.
- Sling the ceiling element and move it to the installation site. Smoothly lower, coordinating the position of the panel using crowbars.
- Check the size of the supporting surface and finally lower the panel to be mounted. Remove the sling elements.
- Anchor the formed floor by fixing the panels to the walls. Place anchors at equal intervals of 2–3 m.
When installing floors in buildings made of various types of cellular concrete, it is important to pay attention to the density of aerated concrete or foam concrete blocks. To ensure the strength and stability of the structure being built, the density of the building material must exceed D500. The panels are laid not on the surface of the cellular blocks, but on a power armored belt located along the perimeter of the building. A reinforced contour made of durable concrete absorbs the load, ensuring the integrity of the walls.
Let's sum it up
When executing installation work When installing slabs, it is necessary to ensure the size of the supporting surface, regulated building codes. You should rely on the results of preliminary calculations. For individual construction, you can use tabular parameters that have been repeatedly tested under conditions practical operation. Compliance with these requirements will ensure the load-bearing capacity of buildings for a long time.
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Introduction to floor assemblies
The assembly of supporting a floor slab on a brick wall is nothing more than the junction of two planes: vertical and horizontal. Many private developers play with this point in different ways, but it doesn’t always work out correctly, much less reliably.
Therefore, to avoid adverse consequences associated with expensive repairs, it is necessary to prepare in advance.
Types of floor materials used
These floors themselves are made of reinforced concrete slabs, the most reliable materials available.
There are just some differences in the production process, this is due to the type of structure:
- Cellular concrete.
- Prefabricated monolithic– the most popular of all presented.
- Made from heavy concrete. This type applies to many materials, since admixtures of heavy concrete are present in various products.
- Multi-hollow.
All of the above-described floors of brick buildings are used in certain conditions, depending on the design of the structure, the load being carried out and the dimensions of the span.
They should be divided into two categories:
- Interfloor ceilings in a brick house - used for multi-level houses. They are mounted into a load-bearing wall on a special lining, which ensures reliable fixation of the product. In this case, the depth from which the ceiling will lie on the wall is very important.
- The attic type does not experience such high loads, so it is mounted into the wall without a lining.
For your information! If you decide to build a multi-story brick house with your own hands, you should give your preference to a floor made of prefabricated reinforced concrete slabs. They have not only increased strength, but also enormous load-bearing capacity, and also, so to speak, affordable installation.
Another feature of the ceiling in a residential building is its ability to isolate the room from extraneous sounds and conserve heat. In this case, not only the use of heat-insulating materials from the attic side of the ceiling, but also insulation of the junction of the walls and the ceiling. Of course, if heat loss through the roof exists (see also the article Making wooden floors in a brick house themselves).
Support node - find a solution
In order for the support of floor slabs on brick walls to withstand high loads, it is not enough to use durable materials; the most delicate approach is required here.
- Firstly, you need to correctly calculate the support unit. Keep in mind that it can only be implemented on a load-bearing wall, but cannot be connected in any way to a partition.
Note! Each product (building material) has its own marking, which indicates its specific features: seismic resistance, load-bearing capacity and others. This applies not only to reinforced concrete slabs, but also to bricks used as load-bearing structures. For example, double sand-lime brick M 150 is not the best solution for building a multi-story building.
- Secondly, all calculations and a plan for solving the problem must be checked against GOST 956-91 and additional design documents. Otherwise, you may be denied construction.
For example, check out the markings of PC 42.15-8T slabs, where PC is the floor with round voids, 42.15 is the dimensions of the product in decimeters (length 4180, width 1490). The number 8 is the maximum permissible load on the slab, which is equal to 800 kgf/m2, and the letter T following 8 is the index of the heavy concrete used for the production of this slab.
There is also a certain standard for how the support of floor slabs on a brick wall should look - from 90 to 120 mm. It is this size that should be maintained, adapting to it.
You must understand that this structural unit is very important for the entire house, both at the design and construction stages. Plus, one more point should be taken into account, which is directly related to the reliability of the ceiling - brickwork, or rather the contact of the wall with the foundation (Find out here how to lay brick partitions).
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, resulting in curvature of the ceiling.
- The width of the foundation should in no case be less than the brickwork. In this case, deformation of the load-bearing walls is inevitable - the load of the ceiling will affect the bricks and weaken the cement mortar.
You also need 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 may be unpleasantly high. The main thing in the construction business is reliability and durability.
One feature to be aware of is that the anchors can be positioned through the slab. However, there is a limit - 3 meters from each other, this is the permissible maximum.
For your information! The anchor is also used to fasten prefabricated reinforced concrete slabs together.
Now you understand what a unit 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 unfavorable moments even at the design stage.
Conclusion
Being aware, it is also necessary to monitor how the work is carried out. The final result depends on the quality and correctness of all stages (read also the article Types of brickwork and general principles brick construction).
It is important not only to lay the slabs correctly, but also to build the foundation, withstand the drying time of the mortar, and lay bricks with a minimum joint thickness, as stated in the instructions. You can do all this yourself, but if you are in doubt, it is better to entrust the work to professionals.
In the video presented in this article you will find additional information on this topic.
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Parameters that determined the amount of support
The depth of the ceiling 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 overlapped span;
- sizes 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;
- magnitudes of point and distributed loads;
- seismicity of the construction area.
All the factors listed above must be taken into account when calculating the reliability of the structure. In accordance with current regulatory documents, the support of the floor slab on a brick wall is taken from 9 to 12 cm, final size determined by engineering calculations during the building design process. With smaller overlaps, the heavy dead weight of the elements, combined with acting loads, will provide direct impact on the edge of the masonry, which can lead to its gradual destruction.
On the other hand, a larger overlap will 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 masonry walls. Also, when the ends of the products approach the outer surfaces of the walls, heat loss in reinforced concrete elements increases 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 lead to an increase in the cost of the structure.
Supporting unit for a floor slab on a brick wall
When erecting brick buildings with floors made of prefabricated reinforced concrete slabs, masonry is carried out in full thickness to the design bottom of the ceilings. Next, the bricks are laid only with outside walls to form a niche into which the slabs can be laid.
In support units, it is important to comply with the following conditions:
- the ends should not rest against brickwork, so for the overlap of 12 cm most often used in practice, the width of the niche is ≥ 13 cm;
- the mortar on which the slabs are laid is of the same brand as the masonry one;
- voids in the channels are sealed at the ends using concrete liners, which will protect the ends from destruction when compressed under loads. The production of concrete liners is carried out at factories with delivery upon purchase of slabs; in the absence of liners, channel voids are filled with B15 concrete directly at the construction site.
Slab reinforced concrete products are placed on the end brick walls with one side. In this case, the minimum support of the floor slab on the end walls is not standardized. But in order to avoid destruction of the product when squeezing the hollow channel, the installation must be carried out in such a way that the masonry laid above the ceiling does not rest on the outermost void of the structure and the shoulders of the moments acting from the load must be of minimal values.
Requirements for the installation of armored belts under floor slabs
In buildings with walls made of blocks made of lightweight concrete (aerated concrete, aerated concrete, foam concrete, polystyrene concrete), having low strength characteristics, the floors must be supported by reinforced belts. The armored belt is installed around the entire perimeter of the building. The height of the reinforced belt under the floor slabs is from 20 to 40 cm. The connection of the reinforced belts with the floor parts must be mechanically strong, for which anchor devices are used or joining with reinforcing bars of a periodic profile using electric welding.
The design has the following requirements:
- the belts should be arranged across the entire width of the walls; for external walls with a width of ≥ 50 cm, a reduction of ≤ 15 cm is permissible for laying insulation;
- reinforcement performed using engineering calculations must provide sufficient mechanical strength to absorb loads from the own weight of reinforced concrete elements and overlying structures;
- concrete ≥ class B15;
- the belt is a kind of cold bridge, so it is necessary to insulate it in order to prevent the destruction of aerated concrete blocks from accumulated moisture;
- reliable adhesion to load-bearing walls.
Supporting floor slabs on aerated concrete blocks load-bearing walls 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 2 sides of the span ≤ 4.2 m - ≥ 50 mm;
- the same for a span ≥ 4.2 m - 70 mm.
Aerated concrete blocks are not able to withstand high loads, the material begins to undergo various deformations. The armored belt, taking on all the loads, distributes them evenly, thereby ensuring that the structure does not collapse.
Installation of floor slabs on gas silicate blocks is also carried out with the obligatory installation of monolithic reinforced concrete belts. The required support values correspond to the above values for walls made of aerated concrete blocks.
During installation work, the following conditions must be met:
- maintaining the symmetry of laying elements in spans;
- the ends of the slabs must be aligned along the same line;
- all elements must be located in one horizontal level(control is carried out using building level), tolerance in the plane of the slabs ≤ 5 mm;
- the thickness of the mortar under the slabs is ≤ 20 mm, the mortar must be freshly prepared, without the beginning of the setting process. Additional dilution of the mixture with water is unacceptable.
It is unacceptable to lay rows of bricks or reinforcing mesh instead of an armored belt.
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When developing drawings of a prefabricated floor, it is necessary to show the nodes for supporting these slabs on the walls, as well as the fastening of the slabs to the walls and to each other with metal anchors (such nodes are developed in detail in series 2.140-1 issue 1 “Details of floors of residential buildings”).
On this drawing support unit shown hollow core slab on a brick exterior wall. The support depth of the slab is 110 mm, if we take into account the 20 mm seam, then in total the niche for the slab is a multiple of the size of the brick, this is convenient for masons. The slab rests on the masonry mortar. The joints between the slabs (10 mm) and between the wall and the slab (20 mm) are carefully filled with mortar. An anchor made of smooth reinforcement with a diameter of 10 mm (reinforcement class A240C or A-I) at one end goes into the wall seam, and at the other it is hooked into a loop and welded. It is recommended to install one anchor on every second slab along each wall, optimally when the anchors are installed in a checkerboard pattern and cover all floor slabs (at least one anchor per slab). Then the floor is considered a single disk, and all the slabs work together.
Welding is performed in accordance with GOST 14098-91, with type 42 electrodes.
The anchor is protected from corrosion by cement mortar grade M100, the thickness of the mortar layer is 30 mm.
The voids of the slabs resting on the outer wall must be filled with factory-made concrete liners, the installation of which is mandatory when calculated resistance in the wall at the ceiling level more than 17 kg/cm 2. If the liners are not installed, the slab will collapse under the load from the wall. It is recommended to rest the slabs with the side with liners on less loaded external walls, and on more loaded ones interior walls– closed ends formed by molding.
You can download the drawing in pdf and dwg format here.
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Supporting unit for a floor slab on a brick wall