Rules for supporting floor slabs on a brick wall. Supporting unit for a floor slab on a brick wall

Building a house is a very difficult process, which is fraught with sufficient quantity pitfalls. These include support units for floor slabs. This is an installation technology on which the strength and service life of the house depends. In such conjugations, horizontal and vertical plane fits together.

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 following types:

Floors between floors.
Attic floors.

The first type is used for houses characterized by multi-level design. 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 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 the minimum support of the floor slab on a brick wall, it is necessary to check all calculations with 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. Plates divide the 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 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.

The reliability of supporting the floors on load-bearing walls ensures safe, reliable and long-term operation of the entire building. Structural stability depends on proper execution engineering structures. Therefore, the support of floor slabs on walls is regulated by SNiP.

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, the final size is determined by engineering calculations during the building design process. With smaller overlaps, the heavy dead weight of the elements, combined with the existing loads, will have a 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.

Slabs on end brick walls reinforced concrete products lie 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 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), which have 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 for 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;
reliability of 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 also performed with the mandatory installation of monolithic reinforced concrete belts. The required support values correspond to the above values for walls made of aerated concrete blocks.

During production 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 at the same horizontal level (control is carried out using building level), permissible deviation 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.

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."

These GOSTs are similar in content, and both GOSTs are valid. According to GOST 9561-91, floor slabs are divided into:

1PC - 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.

In most cases, floor slabs 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 participate in the support: fill round voids with concrete or narrow the cross-section of the voids in this place. 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/m2 (8 kilopascals = 815.77 kilogram-force/m2 ).

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 gaskets 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). In general, the minimum depth of support for the slab must be checked with the manufacturer.

But there are questions regarding the maximum depth of support for the slabs. Different sources give 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, it is better to find out the maximum support value from 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 aligned to create flat ceiling, and the 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 the 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 color) 5 cm thick.

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 of 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-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.

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 ( construction material) has its own marking, which indicates its certain 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 – not the best The best decision 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, 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 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 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.

And now we will tell you about the amount of reinforced concrete support hollow core slab on the wall. What should this value be and what does it depend on, and what is written about this in various literature, including normative ones.

Let's start by looking at what the slab consists of. We will now see a cross-section of a round hollow-core floor slab, and you will see that on one side the hole is wider than on the other. According to the series, the hole that is wider has a diameter of 159 mm, and on the other hand the hole is smaller, and this depends on the pipe itself, which is placed in the formwork at the factory during manufacture.

During manufacturing, the slab should come to your production site with a poured (“solidified”, that is, poured concrete mortar) on one side, and sometimes on both sides. If it comes to you not monolithic, you must definitely do it yourself. This must be done with M100 mortar, or concrete of the same grade as the slab itself. If this is not done, then the amount of load that the edge of the slab can withstand will be 17 kg / cm2, and this is very small. Therefore, make sure that these voids are filled as required by regulatory documentation.

When pouring is done at the factory (it is done during the hardening process of the slab), it is better. The second side of the slab has a smaller hole and can withstand a larger load, it can be 45 kg/cm2, it depends on the width of the support. If the width of the support is 100mm, then the load will be 45 kg/cm2, if the support is larger, the load will be approximately 30 kg/cm2, however, in general this is enough.

Therefore, almost all slabs must be filled with a monolith on the side where the hole is smaller, but on the side where the hole is larger - it depends on the factory, so make sure to pay attention to this during construction.

So, let's return to our question, what should be the amount of support on the wall and what does it depend on. Often we can meet different walls, if it is aerated concrete, then resting the slab on such walls without a monolithic belt is strictly prohibited. Why can’t this be done, even if the stove is supported entirely on a gas block? Even if it is 30 cm, this is wrong, since the deflection of the slab will increase, so the slab will chip off the edge of the block, and subsequently the plaster. And if you do monolithic belt, then concrete will withstand stress better than aerated block.

If the house is being built from brick, then you don’t have to make a monolithic belt, but you need to know exactly what brand of brick and span size.

So, if you have a brick wall, then what determines the amount of support? Firstly, from the material on which they rest, and secondly, from the span of the slab.

There is such a series as 1.141-1, which produces slabs from PK30 to PK65. It states that a slab with a span of up to 4 meters must rest on the wall at least 70 mm, and if it is more than 4 meters, then it must rest on a minimum of 90 mm. You can also refer to the recommendations of the manufacturer's plant, and one of these plants recommends these characteristics to us. At the factory you can find slabs of various heights, these can be 220mm, 320mm and 400mm slabs. The depth of support depends on the length of the span; the larger it is, the greater the height of the slab must be taken, and for each height there is its own nomenclature for supporting the slab.

We can have three types of slab support: on concrete, brick and on a metal beam. Let's take standard height slabs, namely 220 mm. The factory describes the normal and minimum support value as follows: “For a slab with a height of 220 mm, the minimum support value for concrete and metal is 80 mm, for brick 100 mm. The normal amount of support for a slab with a height of 220 mm, for concrete and metal - 100 mm, for brick - 150 mm.

If we take the literature of Soviet times, when more attention devoted to science and practice, the following is written there: “The length of support of the slabs on the brickwork is determined by local compression and is taken to be no less than 75 mm for a span of up to 4 meters and not less than 120 mm for a span of more than 4 meters.”

It turns out that the factory series and literature give us different numbers, and who should we trust? But in our opinion, it is better to believe the series, because if something happens, you will be able to present your claims to the plant.

To summarize: despite the fact that there may be deviations during construction, we suggest taking into account the following figures: for spans (slab length) up to 4 meters - the minimum support is 80mm, for spans of more than 4 meters - 120mm.

Supporting floor slabs on walls

Arrangement of support for floor slabs

Important structural element
Some calculations
Individual construction

During the construction of a building, such an important issue as the support of floor slabs must be taken into account.

Correct and incorrect support of floor slabs.

Important structural element

Floors #8211 load-bearing elements buildings made of reinforced concrete structures. They receive and distribute the loads from their weight and the people and equipment in the building onto walls and supports. With their help, the internal space of the structure is divided into floors, and the attic and basement spaces are also separated.

Scheme of laying floor slabs.

Floors in a building must meet many requirements. They must be strong, rigid, have good soundproofing characteristics, not burn and not allow water to pass through.

The material used for the production of floor slabs #8211 is reinforced concrete. These are mainly multi-hollow structures with voids different forms: polygonal, oval, round. Most often in construction, elements with round voids are used. They are highly durable, technologically advanced and completely ready for installation. Load bearing capacity They have #8211 800 kg/m². They are laid on load-bearing walls located at a distance of about 9 m from each other. They rest on two sides. They are distinguished by fire resistance, rigidity, and long service life. Brick, aerated concrete, foam blocks and reinforced concrete panels are used as materials for the walls on which such overlapping elements will be laid.

Some calculations

To find the amount of support for the floor slab great importance has a base on which it is planned to be laid. It is imperative to take into account the length and weight of the structure, the thickness of the supporting wall, and the seismological stability of the building. In addition, the load and its nature must be taken into account, whether it will be temporary or permanent. Such calculations should be carried out by specialists. For an individual developer, when drawing up a project and installation, the main reference point is the manufacturer’s markings.

Design diagram for a square floor slab, supported along the contour

When using flat overlapping elements, the span can be calculated as follows: you need to sum up the thickness of this element and the distance between the two supports. As for the depth of support of the floor slab on the brick base, this value should be equal to the thickness of the structure itself, but not less than 70 mm. To calculate minimum thickness external wall, which will become the basis for floor slabs, it is necessary to take into account the thermal insulation layer and facing material on the end parts of the latter. Thus, a structure with a thickness of 140 mm must be supported by a base whose thickness is at least 300 mm.

Installation of frequently ribbed structures that have liners requires minimal deepening of the floor slabs onto the base #8211 150 mm. During installation, do not allow hollow liners to enter the wall. If the ribs are reinforced with two rods, then it is necessary to bend them through one on the support. If the rib has one rod, then the clamps will take shear stress.

Reinforced masonry structures #8211 are analogues of flat ones. That's why minimum value the depth of support of these elements can be determined in the same way. They must be at least 90 mm thick and supported on two sides.

Individual construction

In specialized literature on construction work definition is given necessary standards concerning the depth of support of floor slabs.

Supporting floor slabs on walls

This figure is within the range of 90-120 mm. For more precise definition of this value, certain calculations must be made, which take into account the length and weight of the structure, the thickness of the supporting wall and the material from which it is made. The expected load must also be determined.

For example, the use of a slab 6 m long requires a depth of support on a brick base of at least 100 mm. When using structures made of reinforced concrete or steel, the permissible depth is at least 70-75 mm; for walls made of foam blocks and aerated concrete #8211, at least 120 mm.

The support depth of the floor slab is determined:

- from the condition of the strength of the slab against local compression, that is, it must be such that the concrete of the slab in the area with which it rests on the wall does not collapse. Indicated in series for slabs, usually at least 90 mm, and taking into account the hands of the builders - 120 mm

- depending on the strength of the wall material. For a 380mm brick wall made of brick grade 75 and above, 120 is sufficient.

Is there any reason why they don't allow it anymore? In theory, 250 mm would sit more firmly on the wall.

The reason is that the operation of the stove changes. The slab becomes pinched in the wall and turns from a beam into a continuous one, which is not desirable and may turn out to be weaker. The support of the slab on a brick wall is usually 120-150mm.

The holes in the voids are covered with a solution, reason - possible deformation in the compression zone from the load. How to cover 250 mm? mystery)

When loads at the top level of the slab are less than 17 kg/cm2 (450 tons per 1 linear meter of a 380 mm thick wall), the voids in the slabs are not filled; when loads are more than 17 kg/cm2, the voids are filled with liners in the factory.

All of the above is for slabs of the 1.141-1 series.

The support of floor slabs in construction is a really important issue. Floors are load-bearing elements of a building and distribute the load of the entire weight along the walls and supports.

Building codes have special instructions on this matter for each type of floor. In addition, in a particular case, the basis where they will be laid is also of great importance. It is necessary to take into account the following parameters:

length, weight of the structure
thickness of the support wall
stability of the building (including seismological).

Based on this, it is clear that calculations must be carried out by specialists.

There are calculations for a square floor slab (depth 70 mm). When installing frequently ribbed structures that have liners - 150 mm. Reinforced masonry structures, like analogues of flat ones, must have a minimum support depth of 90 mm.

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Floor slabs

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."

These GOSTs are similar in content, and both GOSTs are valid. According to GOST 9561-91, floor slabs are divided into:

1PC - 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.

Manufacturers produce slabs of different sizes; you can almost always find the size you need.

Floor slabs have a bottom (ceiling) and top (floor) side.

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)":

But there are questions regarding the maximum depth of support for the slabs. Different sources give completely different values, 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 is will. 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, it is better to find out the maximum support value from the manufacturer.

If the wall is built from “weak” wall materials such as 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.

Error 404

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/reinforced belt on a cement-sand mortar with a thickness of 1-2 cm, 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.

The laying of floor slabs must be done before the construction of 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. Typically, the width of the gap is obtained “by itself” when calculating the required number of slabs, their size and the distance that needs 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 that the monolithic floor is installed rigidly, especially if a staircase will rest on it. The space formed between the 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 load-bearing external wall, 50 cm thick, includes a slab with a support of 12 cm, which is insulated at the end with 5 cm thick EPS (orange color).

See also:

Supporting floor slabs

Naboka A. A. Construction of reinforced concrete interfloor slabs according to metal beams in the old fund // StudArctic forum. Issue 1 (5), 2017, DOI: 10.15393/j102.art.2017.923

Main text

They refer to UNESCO statistics according to which more than 50% of all European residential buildings were built in the period before the 50s of the last century. The need for repair or reconstruction large number residential buildings now no one doubts. This is how the regional program operates in St. Petersburg overhaul common property in apartment buildings St. Petersburg, for which it is planned to allocate about 32 billion rubles from 2017 to 2019.

Carrying out such a volume of work requires the involvement of a large number of specialists in the field of design. The work contains design solutions for the installation of a new interfloor ceiling in order to facilitate, reduce labor costs and optimize the design process. It is worth noting that the design solutions given are not binding and, in the opinion of the author, are purely advisory in nature and may contain errors and inaccuracies. The application of a particular solution must comply existing standards and be confirmed by calculations.

The building structures of the old housing stock are not only outdated - outdated layouts and the quality of engineering equipment do not meet modern standards, but also physically - individual structures outlive their operational period and are not able to meet the strength and reliability requirements imposed on them at the time of construction. Main reasons physical wear and tear are both time, a long period of use, and operating conditions - untimely and improper care, repairs.

Defects and damage, as well as the reasons for their occurrence characteristic of a particular type of structure, can be found in.

We are interested in overlaps. The most common types of floors in old apartment buildings are floors on metal and wooden beams. Floor structures are shown in Figures 1 and 2.

Picture 1. The most common design of interfloor ceilings on wooden beams in the old foundation

Figure 2. The most common design of interfloor ceilings on metal beams in the old foundation

When carrying out a major overhaul, it may be discovered that the existing load-bearing beams are in poor condition and require replacement. Then there is a need to install a new floor. The easiest to implement is reinforced concrete floor on metal beams using a profile sheet as permanent formwork. Further solutions for the arrangement of this floor will be considered.

First of all, you need to install the metal beams. It is better to use rolled profiles as load-bearing beams. Figure 3 shows a node for supporting a metal beam on a load-bearing brick wall of a house.

Figure 3(a). Beam support unit on brickwork

Figure 3 (B). Supporting unit for a beam on brickwork. Section A-A

Figure 3 (B). Supporting unit for a beam on brickwork. Section B-B.

Where, 1 is a stiffener; 2 - support sheet.

The stiffener is installed to ensure the stability of the beam and prevent bending of the I-beam flange. The support sheet is necessary to distribute the load on the brickwork.

Other options for the design of the support unit can be found in.

The span between load-bearing walls sometimes reaches 6 m or more, and it is not possible to deliver a metal beam to the mounting mark in one piece due to its large weight. Narrow entrances, impossibility of arrangement lifting mechanisms and equipment for lifting beams - all these are the difficulties that builders encounter. Then it becomes necessary to make an equal-strength installation joint, shown in Figure No. 4.

Figure 4. Equally strong assembly joint of beams.

The most popular is the assembly joint, in which the top and bottom plates are the same in width and wider than the I-beam flanges. But in construction conditions for the convenience of carrying out welding work The upper plate can be made narrower than the I-beam shelf, then the lower one should be enlarged. (This is exactly the joint shown in Figure 4).

All metal elements must be protected from corrosion. Standard solution- a layer of GF-021 primer and 2 layers of PF-115 enamel. Fire protection measures for metal structures should also be taken into account.

After installing the beams, they begin to install a reinforced concrete slab along the top flange of the I-beam and inter-beam filling.

The predominant way to install reinforced concrete slabs in the old foundation is to use corrugated sheets as permanent formwork. (If the designer decides to use a profiled sheet also as working external reinforcement, the requirements specified in c. should be taken into account).

Profiled sheets should be joined together along the longitudinal edges with an overlap using self-drilling screws or rivets with a pitch of no more than 500 mm. They should be attached to load-bearing metal beams using metal screws in each corrugation on the outer supports and through the corrugation in the intermediate ones.

The profile flooring should be selected depending on the pitch of the beams so that it can withstand the load from the weight of the slab until it gains strength.

Figure 5 shows a possible floor reinforcement scheme.

Figure 5. Scheme of reinforcement of a floor slab using a profiled sheet.

The reinforcement consists of longitudinal rods laid in each corrugation of the corrugated sheet and the top reinforcing mesh in increments of 150-200 mm. The frame elements are connected either by welding or using steel wire.

Figure 6. Flooring on metal beams using profiled sheets as permanent formwork

Sound attenuation in reinforced concrete slab the overlap is too small, so to ensure comfortable conditions accommodation and noise reduction requires additional sound insulation. There is a wide selection of heat and soundproofing materials and depending on the budget, you can select the required material. To fix the material on the bottom shelf, use a profile sheet or separate profiles. As finishing can be applied cladding panels from plasterboard.

At the end the overlap pie will look like shown in Figure 7

Figure 7. The final overlap pie

This overlap will allow you to implement any layout; however, the partitions should be made of lightweight materials, for example, gypsum plasterboard. WITH possible options partitions can be found in.

It is worth noting that the installation of such an overlap may be accompanied (depending on the type of initial overlap) by an increase in loads on the walls and foundation. When replacing floors on more than just one floor, an inspection should be carried out to ensure that the walls, foundation and base are able to withstand the design loads.

Conclusion.

A sharp increase in the volume of major repairs and reconstruction work carried out in the old building indicates the need to develop standard solutions.

The article contains design solutions and recommendations for the construction of a new floor, which are widely used in rear reconstruction. All accepted materials must be certified and comply with current regulatory documents.

Bibliography

1. Savyovsky, V.V. Repair and reconstruction of civil buildings / V.V. Savyovsky, O.N. Bolotskikh. – Kharkov: Publishing House “Vaterpas” 1999. – 287 p.

2. Decree of the Government of St. Petersburg dated December 8, 2016 No. 1127 (short-term plan for the implementation of the regional program for the capital repair of common property in apartment buildings in St. Petersburg in 2017, 2018 and 2019)

3. Rabinovich G.M. Twice born / G.M. Rabinovich. - Leningrad: Stroyizdat, (Leningrad branch Leningrad, Ostrovsky Square, 6) 1971. - 112 p.

4. Fizdel, I.A. Defects and methods for their elimination in structures and structures (2nd edition, supplemented and corrected) / I.A. Fizdel. – M.: Stroyizdat. 1970.

What is the support depth of floor slabs according to SNiP?

5. TsNIIproektstalkonstruktsiya. Series 2.440-1 Issue 1. Frame and hinge units of beam cages and junctions of crossbars to columns / TsNIIproektstalkonstruktsiya, VNIKTIstalkonstruktsiya Ministry of Montazhspetsstroy of the USSR, VNIPI Promstalkonstruktsiya - approved 12/15/1981 Gosstroy of the USSR ( State Committee Council of Ministers of the USSR for Construction Affairs)

6. JSC "TSNIIPSK im. Melnikov." STO 0047-2005 Steel-reinforced concrete floors with monolithic slab on steel profiled flooring. Calculation and design / JSC TsNIIPSK im. Melnikov", CJSC "Hilti Distribution Ltd" - M. 2005 - 63 p.

7. Knauf company. Product Catalog. Partitions - http://www.knauf.ru - catalog of Knauf products. More details: http://www.knauf.ru/catalog/complete-systems/partitions/

Rules for supporting floor slabs on a brick wall. Supporting unit for a floor slab on a brick wall

Parameters that determined the amount of support

Supporting unit for a floor slab on a brick wall

Requirements for the installation of armored belts under floor slabs

Introduction to floor assemblies

Types of floor materials used

Support node - find a solution

Fixing floor slabs

Conclusion

Supporting floor slabs on walls

Arrangement of support for floor slabs

Important structural element

Some calculations

Individual construction

Supporting floor slabs on walls

Description

Supporting the slabs

Error 404

Insulation

Supporting floor slabs

Main text

Bibliography

What is the support depth of floor slabs according to SNiP?

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