Monolithic flooring on reinforced concrete beams. Monolithic ceiling on metal beams. How a panel frame is formed using permanent formwork

In houses made of brick, concrete or concrete blocks, the floors are usually made of reinforced concrete. They provide exceptional strength and earthquake resistance to the structure, and are also very durable and do not burn, which is important. There are several ways to construct reinforced concrete floors. The most common and universal is laying factory-made floor slabs. Such slabs are ordered from concrete factories and then installed using a crane and a team of workers. In cases where using a crane on a construction site is difficult, or when the house has a non-standard layout and it is difficult to lay out finished slabs, a monolithic floor slab is installed. In fact, you can fill a monolithic slab not only when there is evidence for it, but also simply because you consider it more appropriate. In this article we will tell you how to lay floor slabs and how to pour a monolithic slab. Not all work can be done independently, but it is still worth familiarizing yourself with the technology, if only to control the process on the construction site.

DIY monolithic floor slab

Monolithic flooring has a number of advantages compared to flooring made from ready-made reinforced concrete slabs. Firstly, the structure is strong and monolithic without a single seam, which ensures an even load on the walls and foundation. Secondly, monolithic filling allows you to make the layout of the house more free, since it can rest on columns. Also, the layout can involve any number of corners and crannies for which it would be difficult to select floor slabs standard sizes. Thirdly, it is possible to safely equip a balcony without an additional support plate, since the structure is monolithic.

You can install a monolithic floor slab yourself; you don’t need crane or a large team of workers. The main thing is to follow the technology and not skimp on materials.

Like everything related to construction, monolithic flooring begins with a project. It is advisable to order a calculation monolithic slab ceilings in the design office and do not save on it. It usually involves calculating the cross-section of the slab for the bending moment at maximum load. As a result you will receive optimal sizes for the floor slab specifically in your home, instructions on what reinforcement to use and what class of concrete. If you want to try to perform the calculations yourself, an example of calculating a monolithic floor slab can be found on the Internet. We will not focus on this. Let's consider the option of building an ordinary country house with a span of no more than 7 m, so we will make a monolithic floor slab of the most popular recommended size: from 180 to 200 mm thick.

Materials for the manufacture of monolithic floor slabs:

Formwork.
Supports for supporting the formwork at the rate of 1 support per 1 m2.
Steel reinforcement with a diameter of 10 mm or 12 mm.
Concrete grade M 350 or separately cement, sand and crushed stone.
Bending device for reinforcement.
Plastic supports for fittings (clamps).

Technology for pouring a monolithic floor slab includes the following steps:

Calculation of the floor slab if the span is more than 7 m, or the project involves supporting the slab on a column/columns.
Installation of deck type formwork.
Reinforcement of the slab with steel rods.
Pouring concrete.
Compacting concrete.

So, after the walls have been driven to the required height, and their level is almost perfectly leveled, you can begin to install a monolithic floor slab.

The construction of a monolithic floor slab assumes that concrete will be poured into horizontal formwork. Sometimes horizontal formwork is also called “deck”. There are several options for its arrangement. First - rental of ready-made removable formwork made of metal or plastic. Second - production of formwork on site using wooden planks or sheets of moisture-resistant plywood. Of course, the first option is simpler and preferable. Firstly, the formwork is collapsible. Secondly, it offers telescopic supports, which are needed to support the formwork at the same level.

If you prefer to make the formwork yourself, please note that the thickness plywood sheets should be 20 mm, and the thickness edged boards 25 - 35 mm. If you knock down panels from edged boards, then they need to be tightly adjusted to each other. If gaps are visible between the boards, then the surface of the formwork should be covered with waterproofing film.

Installation of formwork is carried out in this way:

Vertical support posts are installed. These can be telescopic metal stands, the height of which can be adjusted. But you can also use wooden logs with a diameter of 8 - 15 cm. The step between the racks should be 1 m. The racks closest to the wall should be located at least 20 cm from the wall.
Crossbars are placed on top of the racks (a longitudinal beam that will hold the formwork, an I-beam, a channel).
Horizontal formwork is laid on the crossbars. If not ready-made formwork is used, but home-made one, then the longitudinal beams are laid on top cross beams, on which sheets of moisture-resistant plywood are placed on top. The dimensions of the horizontal formwork must be adjusted perfectly so that its edges rest against the wall without leaving gaps.
The height of the pillar supports is adjusted so that the upper edge of the horizontal formwork coincides with the upper edge of the wall masonry.
Vertical formwork elements are installed. Taking into account the fact that the dimensions of a monolithic floor slab must be such that its edges extend 150 mm onto the walls, it is necessary to construct a vertical fence exactly at this distance from inner edge walls.
The last time the horizontal and even position of the formwork is checked using a level.

Sometimes, for the convenience of further work, the surface of the formwork is covered with a waterproofing film or, if it is made of metal, lubricated with machine oil. In this case, the formwork can be easily removed, and the surface of the concrete slab will be perfectly flat. Usage telescopic stands preferable for formwork wooden supports, since they are reliable, each of them can withstand a weight of up to 2 tons, microcracks do not form on their surface, as can happen with wooden log or timber. Renting such racks will cost approximately 2.5 - 3 USD. per 1 m2 of area.

After arranging the formwork, a reinforcement frame made of two meshes is installed in it. For the manufacture of the reinforcement frame, steel reinforcement A-500C with a diameter of 10 - 12 mm is used. These rods are used to knit a mesh with a mesh size of 200 mm. To connect longitudinal and transverse rods, 1.2 - 1.5 mm knitting wire is used. Most often, the length of one reinforcing rod is not enough to cover the entire span, so the rods will have to be connected to each other lengthwise. To make the structure strong, the rods must be connected with an overlap of 40 cm.

The reinforcing mesh should extend onto the walls by at least 150 mm if the walls are made of brick, and by 250 mm if the walls are made of aerated concrete. The ends of the rods should not reach the vertical formwork along the perimeter by 25 mm.

Strengthening a monolithic floor slab is done using two reinforcing mesh. One of them - the bottom one - should be located at a height of 20 - 25 mm from the bottom edge of the slab. The second - the top - should be located 20 - 25 mm below the top edge of the slab.

In order for the lower mesh to be located at the required distance, special plastic clips. They are installed in increments of 1 - 1.2 m at the intersection of the rods.

The thickness of the monolithic floor slab is taken at the rate of 1:30, where 1 is the thickness of the slab, and 30 is the span length. For example, if the span is 6 m, then the slab thickness will be 200 mm. Considering that the grids should be located at a distance from the edges of the slab, the distance between the grids should be 120 - 125 mm (from a slab thickness of 200 mm we subtract two gaps of 20 mm and subtract 4 thicknesses of reinforcing rods).

To space the meshes at a certain distance from each other, they are made from 10 mm reinforcing rod using a special bending tool. special clamps - stands as in the photo. The upper and lower flanges of the clamp are 350 mm. The vertical size of the clamp is 120 mm. The installation step of the vertical clamps is 1 m, the rows should be staggered.

Next step - end clamp. It is installed in increments of 400 mm at the ends of the reinforcement cage. Serves to strengthen the support of the slab on the wall.

Another important element is connector of upper and lower mesh. You can see what it looks like in the photo. It is necessary so that the spaced grids perceive the load as one whole. The installation step of this connector is 400 mm, and in the area of support on the wall, within 700 mm from it, in steps of 200 mm.

Pouring concrete

It is better to order concrete directly from the factory. This makes the task much easier. In addition, pouring the mortar from a mixer in an even layer will ensure exceptional strength of the slab. The same cannot be said about the slab, which was poured manually with breaks to prepare a new portion of the solution. So it is better to pour concrete immediately in a layer of 200 mm, without interruptions. Before pouring concrete into the formwork, it is necessary to install a frame or box for technological openings, for example, a chimney or ventilation duct. After pouring, it must be vibrated with a deep vibrator. Then leave to dry and gain strength for 28 days. During the first week, the surface must be moistened with water, only moistened, and not filled with water. After a month, the formwork can be removed. The monolithic floor slab is ready. For installation of floor slabs, the price includes the cost of reinforcement, concrete, rental of formwork and ordering a mixer machine, as well as a concrete pump. In fact, it comes out to about 50 - 55 USD. per m2 of flooring. You can see how the floor slab is poured with concrete in the video demonstrating the installation of floor slabs.

How to lay floor slabs correctly

The use of factory-made monolithic reinforced concrete floor slabs is considered more traditional. The most popular are PC slabs - slabs with round voids. The weight of such slabs starts from 1.5 tons, so laying floor slabs with your own hands is impossible. A crane is required. Despite the apparent simplicity of the task, there are a number of nuances and rules that must be followed when working with floor slabs.

Rules for laying floor slabs

The prefabricated floor slab is already reinforced at the factory and does not require additional reinforcement or formwork. They are simply laid in a span supported on the walls, following some rules:

The span should not be more than 9 m. This is the length of the slabs that are the largest.
Unloading and lifting of slabs is carried out using special equipment provided by the project. For this purpose, the slabs have mounting loops to which the mounting slings are hooked.
Before laying floor slabs, the surface of the walls on which they will be laid must be leveled. Large height differences and distortions are not allowed.
The slabs should rest on the walls by 90 - 150 mm.
The slabs must not be laid dry; all cracks and technological seams must be sealed with mortar.
The location of the slabs must be constantly monitored in relation to the walls and supporting surfaces.
The slabs are laid only on load-bearing walls, all partitions are installed only after the installation of the floors.
If you need to cut a hatch in the ceiling, then it must be cut at the junction of two slabs, and not in one slab.
The plates should be located as close to each other as possible, but with a gap of 2 - 3 cm. This will ensure earthquake resistance.

If there are not enough floor slabs to cover the entire span, and there remains, for example, 500 mm, then there are different ways to lay floor slabs in this case. The first is to lay the slabs end to end, leaving gaps along the edges of the room, then seal the gaps with concrete or cinder blocks. The second is laying slabs with uniform gaps, which are then sealed concrete mortar. To prevent the solution from falling down, formwork is installed under the gap (a board is tied up).

Floor slab laying technology

During the process of laying floor slabs, there must be clear coordination of actions between the crane operator and the team receiving the slab. To avoid injury on a construction site and to comply with all technological process and the rules described in SNiPs, the construction foreman must have routing installation of floor slabs. It indicates the sequence of work, the quantity and location of equipment, special equipment and tools.

It is necessary to start laying floor slabs from the flight of stairs. After laying the slabs, their position is checked. The slabs are laid well if:

The difference between the lower surfaces of the plates does not exceed 2 mm.
The height difference between the upper surfaces of the slabs does not exceed 4 mm.
The height difference within the site should not exceed 10 mm.

As the installation diagram for floor slabs demonstrates, after laying the slabs, they must be connected to each other and to the walls using metal connecting parts. Work on connecting embedded parts and connecting parts is carried out by welding.

Don't forget to follow safety precautions. It is not allowed to carry out work using a crane in an open area with a wind of 15 m/s, as well as during ice, thunderstorms and fog. When moving the slab using a crane, the installation team should be away from the path along which the slab will move, on the opposite side of the feed. Despite the fact that using the services of a professional foreman and a team of installers significantly increases the cost of installing floor slabs, this is still not the case when you can save money. The foreman must provide the project.

Before ordering slabs from the factory, it is necessary to carry out preparatory work. It is better to coordinate the delivery time of the machine with slabs and the crane at the same time, so as not to overpay for downtime of special equipment. In this case, the installation of the slabs can be carried out without unloading, directly from the vehicle.

Preparatory work before laying floor slabs

First - Smooth surface support. The horizon should be almost ideal; a height difference of 4 - 5 cm is unacceptable. First of all, we check the surface of the walls, then, if necessary, level it with concrete mortar. Subsequent work can be carried out only after the concrete has acquired maximum strength.

Second - ensure the strength of the support area. If the walls are built from brick, concrete or concrete blocks, then no additional measures need to be taken. If the walls are built from foam blocks or gas blocks, then before laying the slabs it is necessary to fill in the reinforced belt. Correct styling floor slabs assumes that the supporting surface must be strong enough to support the weight of the slab and not deform along the abutment line. Neither aerated concrete nor foam concrete have the necessary strength. Therefore, formwork is installed along the entire perimeter of the building, a reinforcement frame made of 8 - 12 mm rod is installed in it, and then everything is filled with concrete with a layer of 15 - 20 mm. Further work can be continued only after the concrete has dried.

Third - install mounting towers. Telescopic supports, as described in the section on installing a monolithic floor slab, are installed in increments of 1.5 m. They are designed to take on the weight of the slab if it suddenly slips out of its place. After installation, these towers are removed.

Installation of hollow core slabs using a crane

After the freshly poured concrete has acquired sufficient strength and has dried, the installation of the floor slabs can begin. For this, a crane is used, the lifting capacity of which depends on the size and weight of the slab; cranes of 3 - 7 tons are most often useful.

Stages of work:

Concrete mortar is applied to the supporting surface in a layer of 2 - 3 cm. The depth of application of the mortar is equal to the depth of support of the slab, i.e. 150 mm. If the slab rests on two opposite walls, then the solution is applied only to two walls. If the slab rests on three walls, then on the surface of three walls. The actual laying of the slabs can begin when the mortar reaches 50% of its strength.

While the solution dries, the crane operator can hook the slings to the slab fasteners.
When the crane operator is given a signal that the slab can be moved, the team of workers must move away from the place where the slab is moving. When the slab is very close, the workers hook it with hooks and turn it around, thereby dampening the oscillatory movements.

The stove is directed to the right place, one person should stand on one wall, and the other on the opposite. The slab is laid so that its edges rest on the wall at least 120 mm, preferably 150 mm. After installation, the slab will squeeze out excess mortar and evenly distribute the load.

If there is a need to move the slab, you can use a crowbar. Its position can only be aligned along the laying area; the slab cannot be moved across the walls, otherwise the walls may collapse. The slings are then removed and a signal is given to the crane operator to pick them up.
The procedure is repeated for all slabs without exception. The rules for installing floor slabs suggest that the slabs should be aligned along the bottom edge, since it is the bottom surface that will be the ceiling in the room. Therefore, the slab is laid with the wider side down and the narrower side up.

You may come across a recommendation that reinforcement must be placed in the area where the slab is supported. Proponents of this method say that it is more convenient and easier to move the stove. In fact, placing anything other than concrete mortar under the slab is prohibited by the technical map. Otherwise, the slab can easily move out of the support area, as it will slide along the reinforcement. In addition, the load will be distributed unevenly.

Laying floor slabs on the foundation is practically no different from laying interfloor slabs. The technology is exactly the same. Only the surface of the foundation must be thoroughly waterproofed before laying the slabs. If the project provides for non-standard support of floor slabs, then special steel elements are used for this. Such work should not be carried out without a specialist.

Anchoring - tying the slabs together - can be done in two ways, depending on the project.

First - tying slabs with reinforcement. Reinforcing rods with a diameter of 12 mm are welded to the fastening embedded elements on the slab. For slabs from different manufacturers, the location of these elements may be different: in the longitudinal end of the slab or on its surface. The strongest connection is considered to be a diagonal connection, when the plates are connected to each other with an offset.

The slab must also be connected to the wall. Why is reinforcement built into the wall?

Second way - ring anchor. In fact, it looks like an armored belt. Formwork is installed around the perimeter of the slab, reinforcement is installed into it and concrete is poured. This method slightly increases the cost of laying floor slabs. But it's worth it - the slabs end up clamped on all sides.

After anchoring, you can begin to seal the cracks. The gaps between the floor slabs are called rustications. They are filled with concrete grade M150. If the gaps are large, then a board is tied from below, which serves as formwork. If the gaps are small, then the floor slab will be able to withstand the maximum load the very next day. Otherwise you need to wait a week.

All modern slabs with round voids are produced with the ends already filled. If you purchased slabs with open holes, then they need to be filled with something 25 - 30 cm deep. Otherwise the slab will freeze. You can fill the voids mineral wool, concrete plugs or simply fill with concrete mortar. A similar procedure must be performed not only on those ends that face the street, but also on those that rest on the internal walls.

The price for laying floor slabs depends on the amount of work, the area of the house and the cost of materials. For example, the cost of PC floor slabs alone is approximately 27 - 30 USD. per m2. The rest is related materials, crane rental and workers, as well as the cost of delivering the slabs. Professional teams have very different prices for installation of floor slabs, from 10 to 25 USD. per m2, maybe more depending on the region. As a result, the cost will be the same as for pouring a monolithic floor slab.

Laying floor slabs: video example

Most often in country houses Of course, wooden floors are installed. But in cottages with 2-3 floors, this structural element of the building can also be poured from concrete. Such floors can withstand heavy loads and at the same time are reliable. However, the construction of such structures, in comparison with wooden ones, is, of course, more expensive. In addition, the technology itself for arranging floors of this type is considered relatively complex. Concrete structures of this type can be poured, for example, using a profiled sheet.

Characteristics

Monolithic floors can be erected using corrugated sheets not only in private homes, but also, for example, in industrial buildings, garages, warehouses, etc. Such structures are quite heavy in weight. But since in this case corrugated sheeting is used as formwork, it takes less concrete to fill them than to install a conventional monolithic slab. Consequently, the weight of the ceiling is reduced. Accordingly, such a slab puts less load on the supports.

The advantages of such structures, in comparison with conventional monolithic ones, also include:

no need to use multi-row reinforcement;

the ability to install the ceiling in a short time;

no need to dismantle the formwork.

In industrial premises, the ceiling filled in this way is usually not even further finished. The profiled sheet looks quite aesthetically pleasing.

Design

Before you start constructing a monolithic floor using corrugated sheets, of course, you should compose it detailed drawing and do everything necessary calculations. Designing such structures is a very complex and responsible matter. Errors in the calculations of monolithic floors can lead to their rise in cost, shortened service life, and in some cases even to the collapse of the structure.

Therefore, the design of such slabs is usually entrusted to specialists. The owner of a house can independently calculate a monolithic floor using corrugated sheets only if he has a special education. You can also create a project for such a slab using software developed for this purpose.

Requirements for floors

In most cases, I-beams are used as beams for such slabs. When designing a monolithic floor using corrugated sheets, the following factors are taken into account, among other things:

each sheet must rest on at least three beams - at the edges and in the center;

beams should be laid at a distance of 1.5-3 m from each other;

along the length, the sheets can be mounted end-to-end when assembling formwork for floors;

the width is overlapped by at least 1 wave;

the layer of concrete mixture after pouring should rise above the waves of material by at least 5 cm;

The reinforcement frame for such a slab should be knitted from 12-8 mm rod.

The surface of the finished slab can be 3 cm vertically away from the edge of the sheet waves. However, pouring in this way is allowed only if a screed is subsequently intended to be poured on it.

Getting settled concrete floors, including corrugated sheeting, only in buildings with heavy walls. It is allowed to support slabs on metal sheets only on brick or block enclosing structures. Equip structures of this type in wooden structures it is forbidden.

Installation of monolithic flooring on corrugated sheets: installation technology

Corrugated ones are laid on I-beams in such a way that their waves are perpendicular to the latter. Most often used for pouring floors roofing material, marked N. It is believed that a sheet with a not too high wave is best suited for the installation of such structures. It is advisable to use such corrugated sheeting under a monolithic floor, primarily because in this case it turns out to be the most durable.

Ribbed ones are fixed metal sheets on I-beams when installing formwork with reinforced self-tapping screws. When using such fasteners, there is no need to pre-drill holes in the decking and beams. Screw in the screws with a drill at low speeds in increments of about 30 cm. The width of the corrugated sheet overlaps is usually additionally secured with rivets.

Attic passage

After the entire opening of the building is closed, vertical formwork walls made of boards are installed along the edges of the future slab. The same elements are installed where it is planned to make an exit to the attic in the future. Experts advise covering the boards before assembly. plastic film. This will make dismantling them much easier later.

After removing the boards from the finished slab, at the point where the attic exits, the corrugated sheeting is simply cut with metal scissors. The operation is very simple and can be performed in a few minutes.

Reinforcement

At the next stage, reinforcement is installed on the formwork made from corrugated sheets and boards. When knitting it, a thicker rod of 12 mm is usually placed parallel to the waves. Perpendicular elements are made from 6-8 mm reinforcement. If desired, you can also purchase a ready-made reinforcing mesh for such an overlap. However, pouring the slab in this case will, of course, cost a little more.

Of course, after pouring the monolithic floor over the corrugated sheet, the frame should be in its thickness. Therefore, the associated reinforcement is lifted above the sheet using special plastic clamps. According to the standards, the connected mesh should be located above the bottom of the metal formwork at a height of at least 1.5 cm. This will allow for a fairly reliable and durable floor to be poured.

When installing a slab on a corrugated sheet, both self-made and purchased reinforcement frames are mounted using the same technology. For knitting mesh with your own hands, you should use strong wire, 1.2-1.4 mm thick.

Additional supports

After the reinforcement frame is connected and installed, the actual pouring of the slab begins. Previously, if necessary, additional steel or wooden vertical supports are installed under the sheets between the beams. Such structures are used if the distance between the I-beams was chosen to be large enough when drawing up the project for a monolithic floor on corrugated sheets. After the slab hardens, the additional supports are simply dismantled.

Pouring the slab

Concrete mix To build monolithic floors on corrugated sheets with your own hands, in the vast majority of cases they use ready-made purchased ones. The fact is that such structures must be poured in one step. Concrete is placed in parts into the formwork, mainly only when installing large ceilings, for example, production workshops.

Of course, cook it yourself right away a large number of cement mortar and pouring it onto sheets will be extremely problematic. Therefore, concrete is laid when installing monolithic floors on corrugated sheets, usually using the following technology:

a concrete truck is ordered to the work site;

feed the solution into the formwork from a steel hose;

As the mixture spreads, all resulting defects are smoothed out manually.

Also, during the pouring process, it is advisable to pierce the concrete with a shovel from time to time. This will avoid the appearance of voids in the finished slab, reducing its strength.

The final stage

Monolithic floors on corrugated sheets, like any other concrete structures, take quite a long time to harden. The slab will gain sufficient strength only 4 weeks after pouring. At this point, you can remove additional supports from under them and begin, for example, building a roof.

While the slab is hardening, you need to carry out proper care. For the first two weeks, the ceiling should be watered at least once a day. Otherwise, surface cracks may form on the slab. And this will certainly lead to crumbling of the top layer in the future. For reliability, the wetted slab can also be covered with plastic film. It is especially important to carry out this procedure in hot weather.

What you need to know

Flood interfloor ceilings Recommended only at above-zero temperatures. Otherwise, such a design will not turn out to be too strong. Sometimes concrete plates made on corrugated sheets and in winter. However, in this case, a mixture of a special composition is used for filling, which increases the cost of the work.

Monolithic ceiling on corrugated sheets: manual pouring guide

During the production of slabs, concrete is supplied to the formwork, thus, in most cases, from a tank using a hose. However, there is a technology for self-filling such structures. In this case, additional sectional adjustable formwork is installed above the corrugated sheet.

In this case, each part of such a structure should be filled at a time. The sections must be positioned across the I-beams in such a way that each individual slab is subsequently supported by at least three beams.

The cutting walls of such formworks are not statically attached to the main frame. After pouring each section, the board is simply rearranged to the same distance. This formwork element is configured in such a way that adjacent finished slabs, after pouring, are interlocked using the tenon/groove lock principle.

Do you need a screed?

The technology for installing a monolithic floor on corrugated sheets is therefore relatively simple. Compared to concrete structures, slabs cast on metal ribbed sheets are usually thinner. After all, in this case formwork gives them additional strength. However, when using a hose to supply the solution, the surface of such ceilings, unfortunately, is usually not particularly smooth. After all, it can be quite difficult for builders to correct it during pouring.

Therefore, after the slab has hardened, in most cases, a concrete screed. You can prepare the mixture for such a leveling coating yourself. Concrete mixed in a cement/sand ratio of 1/3 is usually used to fill the screed. The minimum permissible thickness of such a leveling coating is 3 cm.

Operating rules

The service life of monolithic ceilings, including those cast on a profiled sheet, corresponds to the durability of the main load-bearing elements Houses. That is, this design will never have to be changed in the future. However, such floors can last so long, of course, only if they are used correctly.

The service life of structures of this type may be reduced due to:

exposure to aggressive environments;

frequent changes in humidity.

To ensure that such a monolithic ceiling on corrugated sheets does not have to be repaired or dismantled in the future, communications - heating and water supply pipes - should be laid in the attic in strict compliance with all required technologies. This is especially true for slabs that serve as floors or ceilings for bathrooms, steam rooms, etc. Any leaks over such floors must be repaired immediately.

Monolithic beam floors, ribbed floors.

Reinforced concrete floors. Depending on the construction method, they are divided into monolithic and prefabricated. The advantage of such floors is their high load-bearing capacity. The compressive strength of concrete is used here since the dimensions of these floors can be accurately determined by static calculations. The disadvantage of reinforced concrete floors is high sound permeability.

Monolithic reinforced concrete floors are made at a construction site in formwork. Performing the function of transferring the load from the floor to the load-bearing walls, they also serve as stiffening elements in buildings with a massive frame. To manufacture monolithic reinforced concrete floors, formwork is required, made from a scarce material - wood. Monolithic reinforced concrete floors are divided by shape into slab, beam, ribbed and liner floors (Fig. 84).

Monolithic slab floors. The simplest design of monolithic floors is the Monier slab, in which the reinforcement is placed in tension areas, i.e. in the lower part of the slab, since steel has 15 times greater tensile strength than concrete.

Rice. 84. Reinforced concrete floors a - monolithic reinforced concrete slab; b - reinforced concrete monolithic beam floor; 1 - transverse reinforcement of the beam; 2 - beam; 3 - longitudinal main reinforcement of the beam; c - reinforced concrete monolithic ribbed floor

The slab is usually laid on load-bearing wall, and the length of the surface on which the slab is laid is 10 cm; When using slabs with a thickness of more than 10 cm, the length of the surface on which the slab is laid is equal to the thickness of the slab. Such floors can have a maximum span of 300 cm (see Fig. 84, a) . For larger spans, the reinforced concrete slab is concreted on steel load-bearing beams spanning the large span. Such floors are called slab monolithic reinforced concrete or combined floors with steel load-bearing beams.

Monolithic beam floors. For large spans, floors can have a maximum span of 300 cm. Reinforced concrete beams are laid on the wall; they are connected to a reinforced concrete slab and reinforced. Such floors, invented by the French engineer Ennabic, are called Ennabic floors. Beams are laid at a distance of 130-500 cm from one another. Length of beams to be laid on load-bearing beams brick walls should be 7.5% of the beam span, but not less than 22 cm. Typically, beams are anchored into monolithic reinforced concrete belts with brickwork.

Reinforced concrete beam floors are used in rooms where a flat ceiling is required (basements, warehouses, workshops, etc.), since the axial distance between the beams of this floor is too large to finish a flat ceiling.

The use of reinforced concrete beam floors is cost-effective if there are spans of 6 m (see Fig. 84, b).

Monolithic ribbed floors. If, when using reinforced concrete floors, it is necessary to make a flat ceiling, the axial distance between the beams should be reduced by 0.5-1 m. The cross-section of the beams is smaller, which is why they are called ribs. To prevent the ribs from bulging, they are reinforced over a span of 6 m with one transverse rib (see Fig. 84, c).

The flat ceiling is finished with hemming and lime-gypsum plaster or reed plaster. Before concreting a ribbed reinforced concrete floor, pins or wire with a diameter of 10 mm are placed in the reinforcement so that after concreting and stripping they protrude from the sides of the ribs. Planks 2 cm thick are installed on these embedded parts, the lower edge of which protrudes beyond the edge of the lower rib by 1 cm (Fig. 85, a).

Rice. 85.

a - side mounting; b - slab - base of the filing; c - finishing without slab; 1 - steel rod with a diameter of 8 mm; 2 - mesh

Another method is that when making formwork, the ribs are placed in it before the reinforcement is laid and the plank bottom is secured, after which both ends of the wire are monolied. To the base made in this way, a sheathing of slabs 12-20 mm thick, nailed, is attached. The joints between the plates should not be wider than 15 mm. Simple plaster is applied to the sheathing or lined with reed mat (Fig. 85, b). Sometimes wire is embedded into the slab and ribs and, after stripping, a chain-link mesh is attached to it and lime-gypsum plaster is applied (Fig. 85, c).

Monolithic floors with liners. The big disadvantage of ribbed floors and especially floors with a flat ceiling is the complexity of their construction and the high consumption of wood for the manufacture of formwork and lining. Therefore, floors with liners are more often used. In the places of future gaps between the ribs, liners are placed, which serve as the formwork of the ribs and at the same time as the lower part of the slab formwork. The lower sides of the liners replace the lining with boards and serve as a base for plaster. Inserts are made from various materials of various shapes. The most common are rigid liners made of baked clay, the lower part of which extends to the shelves, forming the lower formwork of the ribs. The liners are placed in horizontal formwork and, after preparing the reinforcement for the ribs and slabs, they are concreted (Fig. 86).

Rice. 86. 1 - plaster; 2 - ceramic liner; 3 - rib reinforcement

The disadvantage of floors with liners is that they are characterized by greater sound permeability than the floors described above, since the liner, after adhesion to reinforced concrete, forms a continuous resonant slab.

Design characteristics

Floors consist of a load-bearing part that transfers the load to individual supports or the wall, and the enclosing structure, which includes ceilings and floors. Based on the material of the load-bearing part, one can distinguish reinforced concrete (reinforced concrete) floors, steel and wooden beams, ceramic and armosilicate. The cost of floors and ceilings will reach 20% of the total cost of the house. The consumption of reinforced concrete for flooring will be up to 60% of the total consumption.

It is worth understanding that the cost of covering should be minimal.
In modern construction, the main material for flooring is reinforced concrete. made of reinforced concrete (reinforced concrete) can be divided into monolithic and prefabricated, concreted in formwork. IN Lately For the first floor, only monolithic reinforced concrete floors and prefabricated floors are used. Prefabricated ones allow you to cover a span of up to 12 m. Speaking about which one is needed, you should know that the consumption of this mortar per 1 m² will be 0.223 m³, and steel - 6.5 kg. This consumption is approximate and may vary slightly.

It is worth knowing that floors must meet the requirements of rigidity, strength, fire resistance, durability, sound and heat insulation if they will separate heated rooms from the outside environment or from unheated rooms. Floors in rooms in which wet processes will occur must be waterproof, and in rooms in which gases are emitted - gas-tight.

In country houses with brick walls, people most often prefer precast reinforced concrete floors with round voids. Their length ranges from 4800 to 6980 mm, width – from 1000 to 2400 mm, and height – 220 mm. Designs with flat voids with a length of 2700-4200 mm with a gradation of 300 mm, a width of 1200-1500 mm, and a thickness of 120 and 160 mm are also used.
Panels for the first floor should be laid on a 10mm thick layer of freshly laid masonry mortar, with a minimum of 120mm of support sealed. In increments of 2400-3000 mm, they are connected through one panel with anchors with a diameter of 8-10 mm. The anchors are attached to the hinges and inserted into the masonry 250 mm from the end of the panel. It is necessary to finish with a bend at an angle of 90 degrees horizontally at 380 mm.

The seams between the panels are filled with cement mortar. Speaking about what composition should be, it is worth knowing that it is 1:4 by volume. The panels are installed using truck cranes.
Installation of reinforced concrete floors

Such designs for the first floor have some valuable qualities. The main ones are durability, great strength and fire resistance. To reduce the number of butt joints and installation operations when designing structures of prefabricated floor elements made of reinforced concrete (reinforced concrete), it will be necessary to strive to enlarge them.

Next we will talk about precast reinforced concrete floors. It is divided into 3 main groups: beam, large-panel and in the form of flooring (slabs). Structures in the form of decking will consist of flat or ribbed elements of the same type, which are laid closely. Speaking about which connection method should be used here, it is worth knowing that you need to fill the gaps with cement mortar.

Similar structures for the first floor consist of a load-bearing part made of reinforced concrete, a thermal and sound insulating layer and a floor structure. The walls and purlins will serve as supports for the decking. The most common are hollow-core decks, having a height of 160 mm if there is a span of up to 4 m, and 220 mm if there is a span of more than 4 m.

In the process of manufacturing decks with vertical voids, concrete consumption will be 15% less than with round-hollow decks. Round vertical voids are formed using pipe liners (the liners are welded to the channels). Flooring that can cover entire rooms is called large panels. In this case, the consumption will be less. The absence of joints in panels within rooms will increase their sound insulation and provide higher quality ceiling finishing.

In order to ensure regulatory sound insulation properties from airborne noise, single-layer panel structures of the first floor, which are made of heavy concrete, must have a mass that exceeds 300 kgf per 1 m².

In the process of installing separate-type floors, in which the sound-insulating capacity of the air gap between the lower and upper panels of a precast reinforced concrete floor is used, and when installing layered floors, it will be possible to ensure the standard sound-proofing capacity with a floor mass of less than 300 kgf per 1 m².

Interfloor large-panel reinforced concrete (reinforced concrete) floors can be designed with a layered floor, with a layered floor and a separate ceiling, of a separate type (of two separate load-bearing panels, with a separate ceiling or with a separate floor). All of the above floor structures have a relatively small mass (less than 300 kgf per 1 m²). Standard sound insulation can be provided by a layered floor structure or by the presence of a continuous air layer in the thickness.

Floor panels for the first floor are made solid, hollow (with round voids) and hipped. A single-layer load-bearing panel is a reinforced concrete slab with a lower surface of a constant cross-section, which is ready for painting, and a flat upper surface.

Single-layer solid reinforced concrete (reinforced concrete) panels, which have a thickness of 140 mm, can cover a span of up to 3.6 m. In order to (about 6-6.6 m), single-layer solid reinforced concrete prestressed panels, which have a thickness of 14- 16 cm, or expanded clay-reinforced concrete, which have a thickness of 18 cm.

The tent panel has the form of a slab, which is framed along the contour by ribs facing in the shape of a cornice. are also arranged from flat reinforced concrete panels, having a thickness of 14-16 cm. The type of overlap will depend on which span should be covered. Maximum span – 12 m.

Installation of beam structure

Interstorey prefabricated reinforced concrete beam-type structures consist of T-beams and infill between the beams. The filler in this case will be a roll of lightweight concrete and gypsum concrete slabs having a thickness of 80 mm and a length of 395 mm, reinforced with slatted wooden or timber frames. The attic floors are made of lightweight concrete slabs, which are 90 mm thick and 95 mm long, reinforced with welded steel mesh.

The joints in the slabs and beams are filled with cement mortar and rubbed. Basement and attic floors It is imperative that they be insulated, and that between floors must be soundproofed. To do this, sand or expanded clay bedding, a layered coating with an elastic gasket should be used in the slabs.

It is recommended that sound and heat insulation in slabs should not be achieved by adding weight building structures. Due to the fact that the elements of beam structures have a relatively small weight, they are often used in buildings that are equipped with cranes of low lifting capacity (about 1 t).

When installing reinforced concrete beam floors in sanitary units, a waterproofing layer should be included in the slabs. For this purpose, 1-2 layers of roofing material are most often glued on top of floorings or panels. bitumen mastic. Beam floors are used if you need to cover a span of 3-7.5 m.

Installation of monolithic buildings

Monolithic structures are made using pre-installed formwork. Such floors on slabs will serve as an additional rigid frame of the building in the process of transferring the load to the load-bearing walls from the floor. Their installation requires a certain professional skill. It must be carried out according to the project under the guidance of a construction specialist.

Fabricating such structures locally has some advantages. To do this, you do not need to have special transport or any lifting equipment. To move and lift concrete, it is enough to have small-scale mechanization equipment.

The basis of monolithic structures is laid in Monier slabs. In it, reinforcement is placed in places of tension, meaning the lower part of the slab. This is due to the fact that steel has a tensile strength 15 times greater than concrete. The reinforcement frame of the slab must be located at a distance from the formwork walls at a minimum distance of 3-5 cm. This is necessary so that the concrete has the opportunity to fill this space.

The span that is covered with a monolithic slab must have a maximum length of 3 m. For plumbing pipelines, care should be taken to install metal or vinyl sleeves that have an internal diameter larger than the pipeline being laid. The gap between the pipeline and metal sleeves must be embossed with tarred tow.

The disadvantage of such monolithic structures is the installation of wooden formwork over almost the entire area of the house. However, this does not mean that you need to install the formwork all at once. The overlap can be done in separate spans, moving the formwork as the concrete sets.

Load-bearing capacity will be provided using reinforcement. Intermediate joints of rods along the entire length are undesirable. On the outside of the ceiling, the minimum layer of concrete must be at least 2 cm. The span must be concreted in one working cycle.

Installation of formwork

To install a monolithic reinforced concrete floor, you will need to install horizontal removable formwork.

Such formwork can be made from wooden shields(from cut boards that are 25-35 mm thick) or waterproof plywood that is at least 20 mm thick. If the formwork panels, which are made of boards, have cracks, a layer of waterproofing film is needed on top of the formwork. It will be needed to ensure that the liquid solution cannot leak out.

Removable formwork should be laid on beams, which will be supported by supporting vertical posts. The racks can be telescopic, made independently from round timber with a diameter of 8-15 mm and beams, or factory-made.

The formwork must be installed without cracks, strictly horizontally. Along the horizontal structure, steel reinforcement is laid and tied using soft knitting wire in the form of a mesh with cells measuring 200x200 mm.

Rebar frame

The reinforcement on the formwork is laid in such a way that there is a gap of at least 25 mm between it and the formwork. To do this, you should use standard special plastic stands or make them yourself from wood, plywood or other material. What material to choose is up to everyone to decide. Any of the above will be needed.

The diameter of the steel reinforcement, which is used to construct a monolithic reinforced concrete structure, will depend on the size of the floor and the load it will bear. It can be within 12-20 mm.

Depending on the strength of the monolithic reinforced concrete floor, there may be 1 or 2 rows of reinforcement. The second row of steel reinforcement is laid on supports made of reinforcement, which are pre-installed on the bottom row and secured with soft binding wire. The height of the stands will depend on the thickness of the reinforced concrete structure being manufactured.

The maximum consumption of reinforcement for the ceiling will be 15-20 kg. It is worth knowing that the consumption may be less.

The most reliable (but not always appropriate) option for interfloor slabs is a monolithic slab. It is made of concrete and reinforcement. Read about the rules for installing monolithic floors in this article. Analysis of the characteristics of types and applications, installation of monolithic floors.

In what cases is it necessary to install monolithic floors?

Monolithic reinforced concrete floor is the most reliable, but also the most expensive of all existing options. Therefore, it is necessary to determine the criteria for the feasibility of its design. In what cases is it advisable to install monolithic floors?

Impossibility of delivery/installation of prefabricated reinforced concrete slabs. Subject to conscious refusal of other options (wooden, lightweight Terriva, etc.).
Complex configuration in plan with an “unfortunate” location interior walls. This, in turn, does not allow laying out a sufficient number of serial floor slabs. That is, a large number of monolithic sections are required. The costs of a crane and formwork are not rational. In this case, it is better to immediately move on to the monolith.
Unfavorable operating conditions. Very heavy loads, extremely high humidity values, which cannot be completely solved by waterproofing (car washes, swimming pools, etc.). Modern floor slabs are usually prestressed. Tensile steel cables are used as reinforcement. Due to their very high tensile strength, their cross-section is very small. Such slabs are extremely vulnerable to corrosion processes and are characterized by a brittle rather than ductile nature of destruction.
Combining overlap functions with function monolithic belt. Supporting precast concrete slabs directly on lightweight block masonry is generally not permitted. A monolithic belt is required. In cases where the cost of the belt and prefabricated floor is identical to or exceeds the price of a monolith, it is advisable to focus on it. When resting it on masonry with a depth equal to the width of the belt, the installation of the latter is usually not required. An exception may be difficult soil conditions: type 2 subsidence, seismic activity, karst formation, etc.

Determining the required thickness of a monolithic floor

For bendable slab elements, decades of application experience reinforced concrete structures, the value was determined experimentally - the ratio of thickness to span. For floor slabs it is 1/30. That is, for a span of 6 m, the optimal thickness will be 200 mm, for 4.5 mm - 150 mm.

An underestimation or, conversely, an increase in the accepted thickness is possible based on the required loads on the floor. At low loads (this includes private construction), it is possible to reduce the thickness by 10-15%.

VAT of floors

For determining general principles When reinforcing a monolithic floor, it is necessary to understand the typology of its operation through analysis of the stress-strain state (SSS). The most convenient way to do this is with the help of modern software systems.

Let's consider two cases - free (hinged) support of the slab on the wall, and pinched one. Slab thickness 150mm, load 600kg/m2, slab size 4.5x4.5m.

Deflection under the same conditions for a clamped slab (left) and a hinged slab (right).

The difference is in the moments of Mx.

The difference is in Mu's moments.

The difference is in the selection of upper reinforcement according to X.

The difference is in the selection of upper reinforcement according to U.

The difference is in the selection of lower reinforcement according to X.

The difference is in the selection of lower reinforcement according to U.

Boundary conditions (nature of support) are modeled by imposing the corresponding connections at the support nodes (marked in blue). For hinged support, linear movements are prohibited; for pinching, rotation is also prohibited.

As can be seen from the diagrams, when pinched, the work of the near-support section and the middle region of the slab is significantly different. IN real life any reinforced concrete (prefabricated or monolithic) is at least partially clamped in the body of the masonry. This nuance is important when determining the nature of the reinforcement of the structure.

Reinforcement of a monolithic floor. Longitudinal and transverse reinforcement

Concrete works great in compression. The reinforcement is tensile. By combining these two elements we get a composite material. Reinforced concrete, which involves strengths each component. Obviously, the reinforcement must be installed in the tensile zone of concrete and absorb tensile forces. Such reinforcement is called longitudinal or working. It must have good adhesion to the concrete, otherwise it will not be able to transfer the load to it. For working reinforcement, periodic profile rods are used. They are designated A-III (according to the old GOST) or A400 (according to the new one).

The distance between reinforcing bars is the reinforcement pitch. For floors it is usually taken equal to 150 or 200 mm.
In case of pinching, a supporting moment occurs in the support zone. It generates tensile force in the upper zone. Therefore, working reinforcement in monolithic floors is placed both in the upper and lower zones of concrete. Special attention should be paid to the lower reinforcement in the center of the slab, and the upper reinforcement at its edges. And also in the area of support on internal, intermediate walls/columns, if any, this is where the greatest stresses arise.

To ensure the required position of the upper reinforcement during concreting, transverse reinforcement is used. It is located vertically. It can be in the form of supporting frames or specially bent parts. In lightly loaded slabs they perform a structural function. Under heavy loads, transverse reinforcement is involved in the work, preventing delamination (cracking of the slab).

In private construction, transverse reinforcement in floor slabs usually performs a purely structural function. Support shear force(the “shear” force) is perceived by the concrete. The exception is the presence of point supports - racks (columns). In this case, it will be necessary to calculate the transverse reinforcement in the support zone. Transverse reinforcement is usually provided with a smooth profile. It is designated A-I or A240.

To support the upper reinforcement during concreting, bent U-shaped parts are most widely used.

Pouring the floor with concrete.

Calculation of a monolithic floor example

Manual calculation of the required reinforcement is somewhat cumbersome. This is especially true for determining deflection taking into account crack opening. The standards allow the formation of a crack in a tensile concrete zone with a strictly regulated opening width. They are completely invisible to the eye, we are talking about fractions of a millimeter. It is easier to simulate several typical situations in a software package that performs calculations strictly in accordance with current building codes. How to calculate the installation of monolithic floors?

The following loads were taken into account in the calculation:

Self-weight of reinforced concrete with a calculated value of 2750 kg/m3 (with a standard weight of 2500 kg/m3).
The weight of the floor structure is 150 kg/m2.
The weight of the partitions (average) is 150 kg/m2.

General view of the calculation scheme.

Scheme of deformation of slabs under load.

Diagram of Mu moments.

Diagram of moments Mx.

Selection of upper reinforcement according to X.

Selection of upper reinforcement according to U.

Selection of lower reinforcement according to X.

Selection of lower reinforcement according to U.

The spans were assumed to be 4.5 and 6 m. The longitudinal reinforcement was specified:

class A-III fittings,
protective layer 20mm

Since the area of support of the slab on the walls was not modeled, the results of selecting reinforcement in the outer plates can be ignored. This is a standard nuance of programs that use the finite element method for calculations.

Pay attention to the strict correspondence of the spikes in moment values with the spikes of the required reinforcement.

Monolithic floor thickness

In accordance with the calculations performed, we can recommend, for the installation of monolithic floors, in private houses, a floor thickness of 150 mm, for spans up to 4.5 m and 200 mm up to 6 m. It is not advisable to exceed the span of 6m. The diameter of the reinforcement depends not only on the load and span, but also on the thickness of the slab. The often installed fittings with a diameter of 12 mm and a pitch of 200 mm will form a significant reserve. Usually you can get by with 8mm at 150mm pitches or 10mm at 200mm pitches. Even this reinforcement is unlikely to work to the limit. The payload is assumed to be 300 kg/m2 - in a home it can only be formed by a large closet completely filled with books. Really effective load in residential buildings, as a rule, significantly less.

The total required amount of reinforcement can be easily determined based on the average reinforcement weight coefficient of 80 kg/m3. That is, to install a floor with an area of 50 m2 with a thickness of 20 cm (0.2 m), you will need 50 * 0.2 * 80 = 800 kg of reinforcement (approximately).

In the presence of concentrated or more significant loads and spans, the diameter and pitch of the reinforcement specified in this article cannot be used for constructing a monolithic floor. Calculations for the corresponding values will be required.