Installation of hollow core slabs. Do-it-yourself installation of floor slabs. Preparing for installation

26.03.2020

The final operation of the zero cycle is the installation of floor slabs on the foundation, which cannot be done without lifting equipment. For most construction works TTK maps have been developed to eliminate injuries and ensure the required quality.

The layout plan of the PC takes into account interfloor technological openings, the range of reinforced concrete products of the plants in the region, the configuration of the building, the presence of ventilation ducts in the internal load-bearing walls. Separately, monolithic sections are indicated, which will have to be poured in place. Delivery of floor slabs is carried out on semi-trailers only with a length of products within 3.2 m. If non-standard panels of greater length are used, they are moved on panel carriers.

The basic rules for laying prefabricated floors are as follows:

it is possible to lay panels only on foundations aligned in a horizontal plane;
with a height difference of up to 5 cm, alignment with a screed is allowed, with large values exclusively with masonry or armored belt, poured into the formwork;
support from 6 cm to reinforced concrete, from 12.5 cm to brickwork;
mortar pastel thickness 15 - 20 mm with obligatory longitudinal reinforcement with a rod round section 10 - 12 mm (reinforcement A240);
adjustment of PC products should be carried out with crowbars in the first 10 minutes, always on tight lines;
concrete plugs for voids are installed in the slab before or after laying, depending on the availability of access to the ends of the product;
anchoring of panels to each other is mandatory, with load-bearing walls depending on the project.

Attention! It is forbidden to crush PC slabs with crushed bricks or crushed stone to level the lower planes of the basement/underground ceiling. Sand or mortar is sifted before the start of work without fail.

Surface preparation

Before placing the slabs on the supporting surface, the foundation is cleaned of mortar, concrete influx, and dirt. For the installation of the first reinforced concrete product, workers need ladders, scaffolding, ladders or scaffolding in the basement. If a prefabricated floor is made on the MZLF foundation, these devices are usually not necessary.

Prior to installation, the quality of the waterproofing of the upper face of the foundation is checked. The film, roll layer must be continuous, be a continuation vertical waterproofing outer and inner walls.

At the same stage, a solution is made at the rate of 2 - 6 buckets for each floor slab, depending on its width. Or a mixture is ordered from a mortar unit of guaranteed branded strength. The mortar bed is laid for one/multiple panels depending on the following factors:

air temperature - in the cold, the cement-sand mixture can freeze, dry out in the heat with a loss of properties;
worker experience - professionals usually lay a bed for 3 - 4 reinforced concrete products, taking into account monolithic sections.

Attention! The working surface of the PC is the lower edge of the plate, so one specialist with a bubble level is needed from below to control the horizontal in two directions, to maintain the flatness of adjacent panels.

Installation of PC panels

Laying of floor slabs begins from the corner closest to the crane or from the wall with a ventilation duct. In any case, two installers are sufficient for slinging. Work is usually carried out from the machine that delivered the PC product to the site in order to reduce the time for unloading. To ensure design support, the length of the spans is pre-measured with a tape measure.

The maps of the TTK indicate in detail how to properly lay the slabs on the foundation with minimal cost time:

slinging for mounting loops - with sling hooks or special lifting devices;
supply of the product to the installation site - the workers are at a safe distance, deploy the panel to the design position with hooks on weight;
laying - after leveling the mortar bed, longitudinal reinforcement is sunk into it in the middle of the supporting surface (3 cm from the edge for reinforced concrete, 6 cm for masonry), the floor slab is leveled on both sides, smoothly lowered into place, the slings remain taut.

If necessary, the reinforced concrete product is adjusted with crowbars during the first 10 minutes relative to the wall axis. Then the lines are loosened completely, the bottom worker controls the horizontal in two directions.

Attention! Alignment with a mortar is carried out when the plate is lifted by all mounting loops, and not by one side. If you lift the PC by two loops, spontaneous movement is possible, squeezing out the solution from under the second edge.

When installing the first slab, the foundation cannot be used for walking by workers, regardless of the width of the tape. It is necessary to use scaffolds, ladders, scaffolding. Then the prefabricated floor is mounted according to the layout scheme, the plates are laid close to each other with long sides. Concrete (rarely polystyrene foam) plugs are usually placed in the voids at the ends after the installation of the entire prefabricated basement floor.

Binding of slabs with reinforcement

Laying rules floors provide plate anchoring according to the following schemes:

edge plates - diagonal tying with wire 3 - 5 mm;
adjacent panels - U-shaped jumpers made of smooth reinforcement A240 with a diameter of 10 mm;
plate / wall - L-shaped anchor with a bend of 30 - 40 cm;
longitudinal connections - between the plates, based on the internal load-bearing wall, smooth reinforcement 10 mm.

Thus, the prefabricated horizontal disk of the floor receives additional spatial rigidity, connection with walls made of bricks, concrete blocks.

Attention: The standard support of PC slabs is 6 - 12.5 cm. In the event of seismic activity, the anchors will ensure the evacuation of people from the building, preventing individual slabs from collapsing.

For normal connection of the PC with internal load-bearing walls, it is enough to put 3 longitudinal anchors for each linear meter of length. All elements are joined with mounting loops by welding in accordance with SP 70.13330 for enclosing and load-bearing structures.

Thermal insulation of joints

After laying the slab, the perimeter of the foundation is leveled brickwork. This material is by default a cold bridge, so it is necessary to lay bars of extruded polystyrene foam or mineral wool between it and the floor slab. Only in this case, heat loss through the floor will be minimal.

Scheme of insulation of the ends of floor slabs.

It is allowed to use solid strips along the entire length of the wall, prefabricated from pieces of insulation. If there are gaps, fill them mounting foam, the characteristics of which are almost similar to the specified heat insulator.

Sealing joints

The above thermal insulation is required exclusively along the outer perimeter of the floor slabs. However, reinforced concrete products have tapered longitudinal edges, so there are seams between them. In addition, the width of the internal load-bearing walls is usually greater than the supporting surfaces of two adjacent slabs. In the first case, it is enough to fill the longitudinal joints of the floor slabs with M100 mortar. In the second option, it is necessary to monolith the site, linking the slabs and the foundation together. To do this, you can use ready-mixed concrete of class B12.5 and higher.

Attention! In areas of internal load-bearing walls, the strip foundation may contain ventilation ducts coming from the underground level. Before laying the mixture on this monolithic section, it is necessary to first perform masonry to continue the channels to the next floor.

This technology makes it possible to lay PC slabs on the foundation with minimal time without reducing the strength of the horizontal floor disk. At the same time, a rigid connection with the load-bearing walls is provided, the safety of residents during natural disasters is guaranteed.

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Currently, in our country, the most popular are three methods of building floors in the house. This is the installation of floor slabs, the device of a monolithic reinforced concrete floor and the device of flooring on wooden (less often metal) beams. We will definitely talk about all these methods and not only. And the first technology that we will consider is the installation of finished floor slabs.

First, a little about the floor slabs themselves. Depending on their shape, all plates can be divided into flat and ribbed. Flat, in turn, are divided into solid and hollow. We are now interested in void ones, because it is this type of slabs that is used mainly in low-rise construction.

Hollow core slabs, in turn, are also classified according to various parameters, such as the shape and size of the voids, the thickness of the slabs, the manufacturing technology of the slabs, and the method of reinforcement.

I will not delve into the topic of classification. It is better to look for this information on the websites of enterprises producing reinforced concrete products (reinforced concrete products). We'd better talk directly about the installation.

The very first point that you need to pay attention to even at the design stage of your future home is the opportunity to purchase in your area exactly the slabs of the sizes that are laid down in the project. Each manufacturer has its own specific range of manufactured products and it is always limited. This is really important and it surprises me that very often developers forget about this recommendation and then they have to either cut one or more slabs or make a monolithic section on the floor. We'll talk more about this below.

Storage of floor slabs at the construction site.

Of course, it's great if you have the opportunity to lay floor slabs immediately upon delivery, directly from the machine that brought them. But most of the time this doesn't happen. Or the driver insists that you unload the plates as quickly as possible, because. he is in a hurry for the next order, or the plates are not laid on the machine in the order you need, or you just bought them in advance and are not going to lay them yet. In all these cases, the plates will need to be stored on your site.

Try to choose a flat surface for this. Never lay tiles directly on the ground. Be sure to put something under the edges of the plate, for example, trim wooden beam. There should be only two linings, at a distance of about 25-40 cm from the edges. Linings cannot be placed under the middle of the plate.

Boards can be stacked up to 2.5 meters high. Make the linings under the first slab higher so that in the event of their possible indentation into the ground when laying subsequent slabs, the first one in no case touches the ground, otherwise it can easily break. It is enough to make all subsequent linings even from an inch (2.5 cm). They must be stacked strictly on top of each other.

Preparation for installation of floor slabs.

Preparation begins even at the moment when the masons kick out the last rows of masonry. The slabs will lie flat and without drops if the upper rows of load-bearing walls are even and lie in the same horizontal plane.

To achieve this, there must be horizontal level marks in all corners of the overlapped room. They are put in the process of building walls using a level, either a laser level, or a hydro level. And when it's done the last row masonry, a tape measure controls the distance from the marks to the top of the walls. It should be the same in all corners. From my own experience, I can tell you for sure that some masons neglect this, especially when they make backing masonry at the same time as the front one, performed “under the bar”.

The top row of load-bearing walls should be bonded. That is, if you look from inside the overlapped room, then only poking should be visible on the load-bearing walls (on which the floor slabs rest) in the uppermost row of masonry.

If the slabs are placed on a load-bearing partition 1.5 bricks thick (i.e., the slabs rest on it on both sides), then the top row of such a partition is laid out in one of two ways:

Before laying floor slabs on walls from various blocks (foam concrete, gas silicate, slag, etc.), it is necessary to make a reinforced concrete belt (usually about 15-20 cm thick). Such a belt is made either by pouring concrete into the formwork, or using special U-shaped blocks around the entire perimeter of the house box, i.e. not only on load-bearing walls, but also on non-bearing ones.

When installing hollow core slabs, the holes in them must be sealed. It is much more convenient to do this in advance, while the plates are still on the ground. In general, SNiP prescribes to seal voids without fail on the side of the slab that rests on outer wall(to reduce the likelihood of freezing of the slab), and from the side that rests on the internal partition, only starting from the third floor from the top of the house and below (to increase strength). That is, if, for example, the house has a basement floor, a floor between the 1st and 2nd floor and an attic floor over the 2nd floor, then it is mandatory to close the voids from the side of the load-bearing partitions only in the basement floor.

I will say that when laying the slabs, we always close up the holes. Moreover, in recent years, more and more hollow-core slabs come from factories with holes already sealed. It's comfortable. If the holes are not sealed, we insert a one-and-a-half brick (maybe even a half) into them and pass the remaining gaps with mortar.

Also, before installing the plates, it is necessary to prepare a site for the crane in advance. Well, if in the place where the crane will stand, the soil is, as they say, native, caked. Worse, when the ground is bulk. If you have a basement, you can not put the tap too close to the house, in order to avoid what is shown in the figure below:

In such cases, it is better to order a truck crane with a longer boom. Also, sometimes in the place where the crane will stand, you first have to put a few road slabs(usually used somewhere). Often this has to be done in the fall in rainy and slushy weather, when the site is so “broken” that the crane simply gets stuck on it.

Floor slab laying.

Three people are enough for the installation of floor slabs. One clings to the slabs, two lay. If desired, you can cope with two, although not always. It happens that when overlapping, for example, the second floor, the installers and the crane operator do not see each other. Then at the top, in addition to 2 people directly laying the slab, there should be another person who will give commands to the crane operator.

Laying starts from the wall on a mortar layer of no more than 2 cm. The mortar must be thick enough so that the slab does not squeeze it completely out of the seam. After the crane operator places the slab on the walls, he first leaves the lines taut. At the same time, with the help of a crowbar, the plate, if necessary, is not difficult to move a little. If the upper surfaces of the load-bearing walls were made even, then the slabs will lie flat, without drops, as they say "from the first approach."

Regarding the size of the support of the plates on the walls, I will give an extract from the document “Manual for the design of residential buildings. Issue. 3 (to SNiP 2.08.01-85) 6. FLOORS ":

Paragraph 6.16.: The depth of support of prefabricated slabs on the walls, depending on the nature of their support, is recommended to be taken at least, mm: when supported along the contour, as well as on two long and one short sides - 40; when supported on two sides and a span of slabs of 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 plates is more than 4.2 m - 70.

When assigning the depth of support for floor slabs, the requirements of SNiP 2.03.01-84 for anchoring reinforcement on supports should also be taken into account.

In our practice, we try to support at least 12 cm, since now it is possible to purchase exactly the plates that are needed. The step of their lengths is 10 cm.

I often hear disputes about whether hollow core slabs can be supported on three sides (two short and one long) and how long it is possible to put the slab on the wall with the long side. From what is written above, it follows that it is possible to support the plates in this way. But it is not so. If you read the indicated SNiP, then it says that slabs that rely on three sides have a different reinforcement scheme than those that rely on only two sides.

The vast majority of hollow core slabs, which are now produced by reinforced concrete factories, are designed specifically to rest on two short sides, so it is not recommended to start them with the long side on the wall. Under a certain load, this can lead to cracking of the plate. The reinforcement scheme and, therefore, the possibility of supporting the slab on a third side must be clarified with the manufacturer.

Also, an error associated with improper loading of the slab is the overlapping of two spans at once (see the figure below):

Under certain unfavorable conditions, the slab can crack, and the place where the crack appears is absolutely unpredictable. If you still use such a scheme, make a cut with a grinder (to the depth of the disk) on the upper surface of the plate strictly above the middle partition. Thus, in which case the crack will pass exactly along this section, which, in principle, is no longer scary.

Of course, it’s good if we manage to overlap only with whole slabs. But the circumstances are different, and yet sometimes some plate (or even more than one) has to be cut along or across. To do this, you need a grinder with diamond disc on concrete, a sledgehammer, scrap and not the most frail man at a construction site.

To facilitate the work, it is better to lay the stove on a lining. Moreover, this lining is placed exactly under the cut line. At some point, the plate will simply break along this line from its own weight.

First of all, we make a cut on the upper surface of the plate with a grinder along the cut line. Then, striking with a sledgehammer from above, we cut a strip along the top of the slab. It is quite easy to break through concrete in the void area. Next, we break through the lower part of the plate with a crowbar (also along the voids). When cutting the slab along (we always chop along the hole in the slab), it breaks rather quickly. When cutting across, if the slab did not break after the destruction of the lower part with a crowbar, a sledgehammer strikes from the side on the vertical partitions of the slab until the victorious one.

In the process of cutting, we cut the falling reinforcement. It is possible with a grinder, but it is safer by welding or a gas cutter, especially when the reinforcement in the slab is pre-stressed. A disk from a grinder can bite. To prevent this from happening, do not cut the reinforcement to the end, leave a couple of millimeters and then break it with a blow from the same sledgehammer.

Several times in our practice, we had to cut the slabs along. But we have never used, let's say, "stumps" with a width of less than 60 cm (less than 3 holes remain), and I do not advise you. In general, when deciding on cutting a slab, all responsibility for possible consequences You take full responsibility, because not a single manufacturer will officially tell you that it is possible to cut a slab.

Let's now see what can be done if, nevertheless, a whole number of plates is not enough for you to completely cover the room:

Method 1- we put the first or last (maybe both) plates without bringing the long side to the wall. We lay the remaining gap with bricks or blocks, hanging them no more than half from the wall (see Fig.):

Method 2- we make the so-called "monolithic section". From below, plywood formwork is placed under the slabs, a reinforcing cage is made (see the figure below) and the area between the slabs is poured with concrete.

Anchoring of floor slabs.

After all the plates are laid, they are anchored. In general, if the construction of a house is carried out according to the project, then an anchoring scheme must be present in it. When there is no project, we usually use the circuit shown in the figure:

The anchor is made by bending the end into a loop that clings to the mounting loop of the plate. Before welding the anchors to each other and to the mounting loops, they must be pulled as far as possible.

After anchoring, we immediately seal with mortar all the mounting eyes in the slabs and rustication (seams between the slabs). Try not to delay this so that construction debris does not get into the rusts, and water does not pour into the eyes during rain and snow. If you suspect that water has got into the slabs (for example, you bought slabs with voids already sealed, and rainwater could get even during storage at the factory), it is better to release it. To do this, after laying, simply drill a small hole in the slabs from below with a perforator, into those voids where the mounting eyes are located.

Especially dangerous is the presence of water in voids in winter time when the house is not yet heated (or not completed at all) and the slabs freeze below zero. Water saturates the bottom layer of concrete, and with repeated freeze-thaw cycles, the slab simply begins to collapse.

Another way of fixing the plates is the construction of the so-called concrete ring anchor. This is a kind of the same monolithic reinforced belt, only it is not made under the slabs, but in the same plane with them, also around the entire perimeter of the house. More often, this method is used on foam concrete and other blocks.

I must say right away that we have never used it because of the much greater laboriousness. I think the ring anchor is justified in more seismic regions than our Nizhny Novgorod region.

At the end of the article, I propose to watch a short video in which we are talking about the choice of floor slabs:

Reinforced concrete slabs are one of the most common types of floors. They provide high strength and allow you to mount a rigid structure in the shortest possible time. Installation of floor slabs is a responsible task that requires certain knowledge in the field of construction. About everything in order.

Types of floor slabs

Before you start mounting a horizontal structure, you must select the type. Reinforced concrete prefabricated structures are produced in the form of:

multi-hollow;
flat (PT);
tent panels with ribs located around the perimeter;
with longitudinal ribs.

Most often, the use of reinforced concrete multi-hollow. They are produced in two types, depending on the method of manufacture:

round-hollow (PC);
continuous molding (PB).

Diagram of a hollow core slab with holes

Hollow-core slabs are time-tested products that have been used in construction for several decades. Under them, a lot of regulatory documents and installation rules have been developed. Thickness - 220 mm. Products are installed according to serial sizes, which creates inconvenience during individual construction.

The manufacturing technology of these plates involves the use of reusable molds for pouring, and before manufacturing non-standard products, you first need to prepare the formwork. Therefore, the cost of the desired size can increase significantly.. Typical PC boards have a length of 2.7 to 9 meters in 0.3 m increments.

Scheme of reinforced concrete products with dimensions

The width of reinforced concrete products can be:

1.0 m;
1.2 m;
1.5 m;
1.8 m

Structures with a width of 1.8 m are purchased extremely rarely, because due to the large weight, the process of installation in the design position is greatly complicated.

PBs are used in much the same way as the previous type. But the technology of their manufacture allows you to give the product any length. Thickness - 220 mm. Width same as PC series. The disadvantage is the little experience of use and the rawness of regulatory documentation.

As additional elements for multi-hollow slabs, flat PTs are often purchased. They are available in thicknesses of 80 or 120 mm and are smaller in size to allow overlapping narrow corridors, closets, bathrooms.

Slab support

The laying of floor slabs is carried out after the preparation of the project or scheme on which the products are laid out. Floor elements must be selected so that they are sufficiently supported on brick wall or expanded clay concrete blocks and laying without gaps in width.

The minimum support for PB and PK series depends on their length:

products up to 4 m long - 70 mm;
products longer than 4 m - 90 mm.

A visual diagram of how to properly and incorrectly support floor slabs

Most often, designers and constructors take optimal value support on the wall 120 mm. This value guarantees reliability with small installation deviations.

It will be correct to pre-position bearing walls houses at such a distance that it is easy to lay the slabs. The distance between the walls is calculated as follows: the length of standard plates minus 240 mm. PK and PB series must be laid with support on two short sides without intermediate supports. For example, PK 45.15 has a size of 4.48 m, 24 cm is subtracted from it. It turns out that the distance between the walls should be 4.24 m. In this case, the products will lie down with an optimal support value.

The minimum support of products of the PT series on the wall is 80 cm. Installation of such reinforced concrete slabs is possible with the location of support points on all sides.

The support must not interfere with the passage of the ventilation ducts. Optimal Thickness bearing inner wall made of bricks - 380 mm. 120 mm on each side goes under reinforced concrete floors, and 140 mm remains in the middle - the standard width of the ventilation duct. In this case, it is necessary to lay as correctly as possible. Offset product to the side air vent will lead to a decrease in its cross section and insufficient ventilation of the premises.

A summary of what has been said:

PK and PB series up to 4 m are supported on two sides by at least 7 cm;
PK and PB series more than 4 m - not less than 9 cm;
PT series - on two, three or four sides at least 8 cm.

Slab storage

Schemes of warehousing products different types

After the scheme has been developed and the products have been purchased, they must be placed on the building site for easy installation in the design position. There are rules for warehousing materials:

you need to lay the elements under a canopy;
the place of storage should be located in the access zone of the crane;
linings are provided under the support points.

Failure to follow the last rule will result in a split in half. PC, PB and PT products work in such a way that the appearance of intermediate supports or a solid base leads to cracks. Laying is performed in the following order:

wooden bars or boards are laid on the ground under the edges of the slab;
I shift the floor element onto the boards with a crane from the machine;
boards or bars are again placed on the laid slab;
unload the second plate from the machine;
repeat points 3 and 4, the maximum storage height is 2.5 m.

masonry requirements

Floor slab calculation scheme

In order to properly install floor slabs, it is necessary to ensure that special requirements for a brick wall are met:

evenness of masonry at the place of laying floors;
laying in three rows until the overlap of reinforcing mesh with a cell of 5 by 5 cm from wire with a diameter of 3-4 mm;
the top row to the lining on the inside should be bonded.

If the slabs are mounted on expanded clay concrete blocks, a monolithic belt is additionally arranged under the floors. This design will help to evenly distribute the load from heavy floors on expanded clay concrete blocks with less strength. The construction technology provides for pouring a monolithic concrete tape 15-20 cm thick onto the blocks.

Floor laying

To carry out the work, at least three people will be required: one performs the slinging, and two install them in the design position. If the installers and the crane operator cannot see each other, another worker will be needed to install the slab to give commands to the crane.

Scheme of laying reinforced concrete products

Fastening to the crane hook is carried out with a four-branch sling, the branches of which are fixed at the corners of the slab. Two people stand on both sides of the support and control its evenness.

When installing a PC, pinching into the wall is carried out in a rigid way, that is, bricks or blocks are laid on top and bottom of the slab. When using ceilings according to the PB series, it is recommended to perform hinged fastening. For this, the plates are not pinched from above. Many builders mount the PB series in the same way as PCs and buildings stand, but it’s not worth the risk, because human life and health depend on the quality of installation of load-bearing structures.

Another important feature of the use of products from the PB series is that it is forbidden to make technological holes in them.

These punches are needed for heating, water supply and sewerage pipes. Again, many builders, even when building multi-storey buildings, neglect this. The difficulty is that the behavior of this type of floors under load over time has not been fully studied, since there are no objects built a long time ago yet. The ban on punching holes is justified, but it is rather preventive.

Slab cutting

Sometimes, in order to install the slab, it is necessary to cut it. The technology provides for the work of a grinder with a disk on concrete. It is impossible to cut the PC and PT slabs along the length, since they have reinforced reinforcement in the support zones. If you support such a cut slab, then one edge will be weakened, serious cracks will go along it. It is possible to cut PB plates along the length, this is due to the peculiarities of the manufacturing method. A bar or board is placed under the cut site, which will facilitate the work.

Separation along the length is performed along the weakened part of the section - the hole. this method is suitable for PC, but not recommended for PB, since the width of the walls between the holes is too small.

After installation, the holes in the areas of support on the walls are poured with lightweight concrete or clogged with mineral wool. This is necessary to provide additional strength in places pinched into the walls.

What to do if it was not possible to evenly spread the products across the width

Sometimes the dimensions of the room do not correspond to the width of the products, in which case all the gaps are driven into one. This space is covered with a monolithic section. Reinforcement occurs with curved meshes. In length, they rest on the top of the ceiling and seem to sag in the middle of a monolithic section. for floors, concrete not lower than B 25 is used.

The technology of prefabricated floors on bricks or blocks is quite simple, but requires attention to detail.

In the design of any building, one of the elements are floors. For the installation of interfloor ceilings, reinforced concrete multi-hollow panels are used, based on longitudinal external and internal walls, runs, crossbars.

Overlappings are basement, attic, interfloor and attic. Regardless of the location and material, the floors must meet certain requirements: be heat, hydro and soundproof, durable, rigid, fireproof.

High strength indicators are characterized by monolithic reinforced concrete floors, which are used in the construction of large objects and are designed to withstand heavy loads. Reinforced concrete floors are fireproof and durable.

The type of construction differs monolithic slab floors(they are made locally) or prefabricated floor slab(consisting of ready-made elements of factory production).

The combination of concrete and reinforcement made it possible to make the design of reinforced concrete slabs strong and durable, working well in bending. Without taking into account the weight of the slab, the calculated load should not exceed 6.0 kPa. A standard reinforced concrete floor slab must withstand earthquakes with a force of 7-9 points. In the construction of buildings, reinforced concrete floor slabs of standard sizes are usually used.

Floor slab marking

PK 60-15-10At- plate 6 meters long, 1.5 meters wide, load capacity - 1000 kg/m2.

The main thickness standard is from 22 to 30 cm (for PPS boards). They also differ in the permissible load on square meter area. Hollow floor slabs, length from 3 to 6.3 meters. Plates PPS up to 12 meters.

Floor slab installation technology

Before installing the floors, check the horizon of the upper supporting parts of the masonry under the floors, which should be in the same plane (the difference in marks within the floor should not exceed 15 mm).

The installation of the panels starts from the end walls, while the installers are on the inventory scaffolds (tables), and the subsequent panels are laid on the previously laid slabs.

Installers use trowels to clean the supporting surface of walls and partitions, working from the floor or from a step-ladder table installed on the underlying floor.

Apply the solution over the entire supporting surface of the wall and spread it with a trowel in an even layer.

The crane driver lifts the panel and brings it to the installation site.

Somewhere at a height of 20-40 cm from the unlocking point, the installers, directing their hands, orient the slab for laying. When ready, give a command to the crane operator and smoothly lower the floor panel.

Leaving the slings taut, the panel, if necessary, is corrected with mounting crowbars, the horizontalness of the surface and the position of the panel in height are checked with a level.

If it is found that the planes of the installed and adjacent panels do not coincide by more than 4 mm, the panel is lifted with a crane, the mortar bed is fixed and reinstalled.

The support length of the plate should not be less than 12 cm.

The thickness of the mortar layer under the floor slabs should not be over 20 mm.

1 - panel

2 - solution

3 - bearing wall

The edges of the panels and floor slabs must rest securely on the walls. It is forbidden to leave the panel in the ceiling with a smaller support width than according to the project. This can cause the concrete to chip at the edge of the floor panels or wall and partition panels, causing the floor panel to collapse.

After alignment, the floor panels are fixed in accordance with the instructions in the working drawings: the mounting loops of the panels are welded to the anchors embedded during the laying of the wall, adjacent panels are fastened together with anchors for the mounting loops. Longitudinal seams(joints) between the panels are sealed with mortar, tightly caulking the seam to its full depth. The joints of the floor panels with the walls are sealed after the installation of the floor.

In the panels, when resting them on the outer walls, the voids must be sealed with lightweight concrete or ready-made concrete plugs to a depth of at least 120 mm. This is done for the purpose of thermal insulation, so that the walls do not freeze in the places where the ceilings are supported in winter. The voids in the panels resting on the internal load-bearing walls are also sealed with heavy concrete or liners, starting from the third floor from the top of the buildings and below. Such sealing is necessary to protect the supporting parts of the hollow floor slabs from destruction under pressure of the overlying structures.

Minimum support length in mm for slabs 6 m long

on the steel structures- 70 mm
on the reinforced concrete structures- 75 mm
for stone structures - 120 mm

Hollow-core floor panels are stored horizontally in stacks up to 2.5 meters high. The bottom row in stacks is laid on wooden linings with a section of 150-150, 100-100 mm. Subsequent linings are placed vertically relative to each other, perpendicular to the voids, retreating 35 centimeters from the edge of the slab.

A reliable and durable house is not only strong stable walls and a leak-proof roof, but also strong seismic-resistant floors. For the arrangement of interfloor ceilings and between the basement and the first floor, solid and multi-hollow reinforced concrete slabs are used. These products are made of solid or lightweight concrete and reinforced with special reinforcement. The ceilings are durable, fire-resistant, resistant to mechanical stress and exceptionally strong. In total, there are several types of reinforced concrete slabs, each of which is used in a particular situation. Therefore, in order not to make a mistake with the choice, it is necessary to pay attention to the marking and understand what is behind the designations in it. But an even more important and responsible task is the laying of reinforced concrete slabs, which is carried out with the help of a crane and a team of workers. We will talk about how to lay reinforced concrete slabs on floors in accordance with the TTK in this article so that you can control the progress of the work.

What are reinforced concrete slabs

It may seem to an uninitiated person that reinforced concrete floor slabs are all the same, you just need to call the factory and say the required quantity. In fact, reinforced concrete factories produce slabs and blocks various designs, destinations and even from concrete of different grades. Therefore, first of all, pay attention to the labeling of the plates.

Marking of reinforced concrete slabs

For example, brand PK57-15-8T means:

PC- name of the product / type of plate. In this case, a floor slab with round voids.

57-15 - dimensions of reinforced concrete slabs indicated in dtsm. In this case, the plate is 5680 mm long and 1500 mm wide.

8 - allowable load on the plate. In this case, the design load is 800 kgf/m2.

T- brand of concrete. In this case, heavy concrete is used.

Sometimes the marking indicates the thickness of the reinforced concrete slab. Then it looks like P-27-15-12-8T. This is the designation of a reinforced concrete solid slab 2690 mm long, 1490 mm wide, 120 mm high, with a load of 800 kgf / m2 from heavy concrete.

Types of reinforced concrete slabs

As we have already found out, the first letter values in the marking indicate the type of plate. Let's find out what they are and what lies behind them.

P - reinforced concrete solid slabs, are used for installation of overlappings in residential and public buildings. Available in different sizes: length from 1790 mm to 6260 mm, width 1190 - 1490 mm, thickness 120 mm, 160 mm, 220 mm. The weight of a solid reinforced concrete slab depends on its size and ranges from 0.625 tons to 3.6 tons. For example, the P-48-12-22-8AT5 slab weighs 2.65 tons, and the P-30-15-16-8A3 weighs 1.775 tons. Such slabs are much heavier than multi-hollow ones. Slabs with a height of 160 and 220 mm provide sufficient soundproofing of the room due to their mass, but if slabs with a height of 120 mm are used, then additional soundproofing measures must be taken, for example, to make layered floors.

PC - reinforced concrete floor slabs with round voids. They are also used for floors, but unlike solid slabs, they provide exceptional sound and heat insulation of the room due to the air contained in the voids. Available in the following sizes: slabs 100 mm wide have a length of 238 mm to 1198 mm; plates with a width of 120 mm have a length of 168 - 898 mm; plates with a width of 150 mm have a length of 238 - 898 mm. The height of the plates with round voids is the same - 220 mm. It is advisable to immediately find out information about how much a reinforced concrete slab weighs from the manufacturer on his website. For example, the most commonly used slab PK45-12-8 weighs 1.58 tons, the long slab PK72-15-8 weighs 3.33 tons, and the product PK120-10-8 with dimensions 1198x100x22 weighs all 5 tons.

PS - reinforced concrete slabs for special purposes. This category includes plates for balconies, loggias, bay windows and for floors sanitary facilities. Their main difference from other plates is the way they support and the presence of additional holes for laying water and sewer pipes. The height of such plates is 200 mm.

ETC - ribbed reinforced concrete floor slabs. They are used for the installation of ceilings of brick residential and public buildings, as well as for the arrangement of the supporting base of the roof. They are also sometimes called "tented", as their size allows you to cover the room completely. The length of such plates can reach 18 m, width 3 m, and height 300 - 600 mm.

RP - reinforced concrete slab spacers. Installed between the columns of buildings. Spacer floor blocks may also be called. Usually their length does not exceed 1.5 m.

Fri - heavy concrete slabs. Used for ceilings between columns in public buildings on the ground floor.

In addition to the above, there are also light concrete slabs, as well as lightweight PNO slabs, which can withstand the same load as heavy concrete, although they have less weight and thickness.

For reinforced concrete slabs, the price depends entirely on their size and type. For example, a PK55-12-8 slab costs 150 USD. each, the most expensive plates large sizes PK76-15-8 - cost 500 USD a piece.

Reinforced concrete slab for foundation

All types of plates listed above are manufactured at the factory and purchased from ready-made. But there is one more category - reinforced concrete foundation slabs. Such plates are made directly at the construction site.

At the place where it is planned to arrange a monolithic slab foundation, excavation is carried out, tamping of the base, backfilling with crushed stone and sand, and even more thorough tamping. Then formwork is formed from metal shields with props.

Next, the reinforcing cage is connected or welded, which is lowered into the formwork. For reinforcement, a rod 8 - 12 mm in diameter is used. Then everything is poured with concrete. After solidification, a monolithic foundation slab is obtained - strong, without cracks, with exact dimensions and the required thickness. Typically, such a foundation is required for moving soils.

Technology of work with reinforced concrete slab

The most popular slabs in private housing construction are multi-hollow reinforced concrete slabs with round voids. They can be ordered at the manufacturing plant, from where a truck with goods will arrive at the appointed time. But what to do next? How to store these plates so that they do not crack? And then, when the installation of the plates begins directly: how to cut off the excess? How to cut a hatch hole in the attic? There can be many similar questions, so let's take a closer look at the technology of working with reinforced concrete slabs.

How to store reinforced concrete slabs

Despite the strength of reinforced concrete slabs, the possibility of cracks on them is not ruled out. There are only two reasons - improper transportation and improper storage. Considering how much a reinforced concrete slab costs, each of them must be handled with care.

Storage of reinforced concrete slabs:

Only in a horizontal position.
At a sufficient height so that the slabs do not touch the ground.
Under the plates, it is necessary to put a solid, reliable base that can withstand a lot of weight, while it should not get wet and rot. Otherwise, moisture may enter the plate, it will get wet and cracks will appear.
The height of the base must be such that even if it sinks, the slabs do not touch the ground. If the lower plate comes into contact with wet ground, cracks may appear not only on it, but also on the higher ones.
Between the plates in one stack are stacked wooden slats 40 - 50 mm thick. They should be located strictly one above the other and at a distance of 20 - 40 cm from the edge.
The maximum number of plates in one stack, subject to a sufficiently strong foundation, should be 8 - 10 pieces.
Do not store them in a vertically inclined position, leaning against a wall.

These tips will help keep the plates from cracking.

How to shorten a hollow core concrete slab

Among all the standard products that the plant can produce, you can always find plates of the right size. But there are situations when different reasons the plate must be shortened either in length or in width. To do this, you need a grinder, a crowbar and a hammer-cam.

Lay the plate horizontally on the lining.
We apply a marking line on the surface of the plate, along which we will cut.
The lining should be strictly under this line.
With a grinder with a disc for concrete, we cut the slab along the line, cutting upper part plates.
With a hammer-cam, we tap the plate in place of voids along its entire width. Usually 3 - 5 blows are enough to cut the slab in the place of voids.
To cut the ribs, we strike them with the same fist, only not from above, but from the side.
A half-destroyed piece of the slab will sag under its own weight, so that scrap can be easily pushed between the parts. Using a crowbar, we break through the bottom wall in the thinnest place. round hole plates.
There should be reinforcement below, we clean it from the remnants of concrete and cut it with a grinder.

The edge of the slab will not be as smooth as the factory product, so it must be deepened to a sufficient distance on the support wall.

Cutting the slab along / along the length:

We also lay the plate on supports in a horizontal position, draw a cut line.
Bulgarian make an incision along the line.
Then tap with a hammer along the entire line. It will be easy to destroy the top wall of the slab, since the incision will run along the line of the hollow hole.
We destroy the bottom wall in the same way.
If there are reinforcing bars with a diameter of 3 - 8 mm, we cut them with a grinder.

Important! Please note that the reinforcement in a reinforced concrete slab can be stressed, so it cannot be cut to the very end. Otherwise, the armature may pinch the grinder disc. The rod is not cut to the end, and the remaining piece is beaten off with a hammer or crowbar.

How to lay reinforced concrete slabs if they are not enough for the width of the room

What to do if the total width of all the plates is not enough to cover the entire room. It remains, for example, 500 mm, which can be cut off from the new plate, or you can try to repair it in another way.

Method 1. Leave gaps on the sides:

The total gap is divided into two parts of 250 mm. The first floor slab is laid at a distance of 250 mm from the edge of the wall.
All other plates are laid end-to-end, without gaps.
There should also be a gap of 250 mm between the last slab and the wall.
We take a cinder block with a length of at least 500 mm, lay it with the butt side to the slab on the cement mortar.
We carry out masonry from a cinder block according to the model, resting it with a poke into the slab. On both sides of the room.

When the wall continues to be built, its masonry will press the cinder block even more and fix it completely. For greater reliability, when performing floor screed on the top floor, you can use a reinforcing mesh made of a rod with a diameter of 6 mm.

Method 2. Leave gaps between the plates:

We distribute the total size of the gap between all the plates. For example, the width of the room is 7800 mm, the plate is 1200 mm wide. We make calculations: 7800/1200=6.5. We multiply the whole number of plates by the width of each 6x1200 \u003d 7200 mm, subtract from the total width of the room 7800 - 7200 \u003d 600 mm. We have 6 whole plates, so there will be 5 gaps between them, we divide 600/5 = 120 mm. In total, we should have five gaps of 120 mm.
Lay the first slab against the wall.
The next with an indent of 120 mm.
All the rest are also indented 120 mm. The latter should be adjacent to the wall.
We tie up the formwork under the gaps.
Inside we insert a frame of reinforcement and tie it to the plates.
We fill with concrete.

All further work can be continued only after the concrete in the gaps between the slabs has gained maximum strength.

How to cut a hatch to the attic in a hollow reinforced concrete slab

When laying reinforced concrete slabs on an attic floor, there is almost always a need to cut a hatch leading to the attic in the ceiling.

The main rule: the hatch is always cut at the junction of two plates, and not in one plate.

The permissible dimensions of the hatch depend on the width of the reinforced concrete slab and its load. The wider the plate and less loaded, the larger the hatch can be cut. The dimensions of the hatch are selected based on the dimensions of the stairs: 600x1200 mm, 600x1300 mm, 700x1200 mm, 700x1300 mm and 700x1400 mm.

The large side of the hatch is placed along the slabs. For example, a 600x1200 mm hole is made like this: an incision is made at the junction of the plates, then one plate is cut into 300 mm, the opposite one into 300 mm, and then a cut is made along 1200 mm.

How to lay reinforced concrete slabs

We figured out the main questions about working with slabs, now the most important thing is laying floors. Despite the seeming simplicity of the work algorithm, there are still such nuances that you must know and take into account. Even before ordering the slabs from the factory, it is necessary to carry out all the preparatory measures, because when the machine arrives with the slabs, everything should be ready for laying.

Preparatory work

Task one - ideal bearing surface. This refers to an ideal horizon without a monstrous height difference of 4 - 5 cm. This is unacceptable. We check the surface of the walls, if there are significant flaws, we level the plane with a concrete solution. Accordingly, you will have to wait until it gains maximum strength, and only then start laying.

Task two - support zone strength. If the house is made of stone materials - brick, concrete, blocks, then no additional action is required.

Important! If the walls are made of gas blocks or foam blocks, then before laying reinforced concrete floor slabs, it is necessary to fill in the armored belt. Formwork is carried out along the entire perimeter of the building, a reinforcing cage made of a rod of 8 - 12 mm is inserted inside. Then everything is poured with concrete. Further work is possible only after the concrete has hardened.

Task three - installation of mounting towers. They are needed in order to take on the weight of the plate, if for some reason it slips off the supporting surface. The tower is used only during the installation process, then it is removed.

Laying reinforced concrete slabs with a crane

When all preparatory work completed, everything that needs to dry and gain strength, dried up and gained strength, you can order plates. For their unloading and laying, you will need a crane, depending on the size and weight of the reinforced concrete slab, it can have a lifting capacity of 3 to 7 tons.

It is possible to carry out laying of plates directly from the car without unloading. To do this, the foreman at the construction site must have project documentation for the house, which indicates the layout of the plates.

Laying reinforced concrete slabs - scheme

Stages of work:

First you need to prepare the surface of support. At a depth of 150 mm, a concrete mortar is applied with a layer of 2 - 3 cm. It is necessary to cover the entire surface on which the slabs will now be laid. If the method of support is on two sides, then only from opposite walls. If the method of support is on three sides, then it is necessary to apply the solution on three walls. You can lay the slab on top when the solution gains 50% of its strength.
At this time, the crane operator can hook and lift one of the plates.
A signal is given to the crane operator, you can lower the plate to the prepared place. The person moves to a safe distance. Holding the slab with hooks, unfold it to dampen the rocking.

When the stove is already very close, two people - one on one wall, the other on the opposite one, gently guide the stove to the right place. The slab should rest on the walls at least 120 mm, preferably 150 mm. The plate will squeeze out the excess solution and take a convenient place, evenly distributing the load on the base.
After the plate is completely leveled, which can be done with a crowbar, the slings are removed from the mounting ears. Alignment of the slab can only be done along the laying area, in no case across, otherwise the walls may collapse. A signal is given to the crane operator to pick up the slings.

The procedure is then repeated for all other plates. In this case, it is necessary to align the plates along the bottom edge, which will be the ceiling in the room. To do this, the plates are laid with the wider side down, and the cone-shaped notch up.

Important! In some sources, you may come across a recommendation, in addition to the solution, to lay reinforcement under the plates in the area of \u200b\u200bsupport. This is due to the fact that it is more convenient to move and level it in this way than without anything. In fact, it is impossible to lay reinforcement, this is prohibited by the TTC. Firstly, the load will be unevenly distributed, and secondly, the plate will easily slide over the reinforcement, so it can move out of place.

If provided non-standard option supporting the plate, then there are special steel elements for this. But it is better not to perform such work without a specialist.

Binding of plates to each other - anchoring

The so-called anchoring can be carried out different ways- binding the plates together with reinforcement or arranging an annular anchor in which the plates will be clamped from all sides.

Rods with a diameter of 12 mm are welded to special fasteners on a reinforced concrete slab, connecting the slabs to each other. Different manufacturers have different arrangements for such elements. It is considered the most optimal when these rods are located diagonally to the plate, i.e. connect the points not at the same level, but with an offset.

Anchoring of plates is carried out not only among themselves, but also with the wall. To do this, reinforcement must be embedded in it in advance.

The ring anchor is somewhat reminiscent of an armored belt. A formwork 10–15 cm wide is made along the entire perimeter of the slabs, a frame is inserted into it, in the corners of which the reinforcement is bent. Then concrete is poured into the formwork. The resulting structure is very durable.

Sealing joints between reinforced concrete slabs

The joints between the floor slabs, they are also called rusts, are filled with fine-grained concrete of the M150 grade. If the gaps are large, then a board / formwork is installed under them. All work on sealing rusts begins only after all the plates are interconnected. The stove will be able to withstand the full load the very next day. Naturally, if the gaps between the plates are not too large.

Sealing voids at the ends in slabs

The voids at the ends of the plates must be filled with something at least 20 - 30 cm deep. This is necessary so that the plates do not freeze and do not let the cold in from the street. You can push into voids mineral wool, you can fill them with concrete mortar, plug them with ready-made concrete plugs or fill them with butovka bricks and seal them with mortar.

It is necessary to close the voids in the floor slabs not only from those sides that rely on the outer walls, but also from those that are inside the house and rely on the internal partitions.

All work on laying the plates takes several hours, from 2 to 4. Since the crane is paid hourly, it can be released immediately after laying the slabs on the ceiling. And anchoring, filling of rusts and voids at the ends can be done independently, slowly and without looking back at the time.