Reinforced concrete floors are the most reliable and durable and therefore are currently widely used in civil engineering.
By device method they are:
■ monolithic,
■ teams and
■ prefabricated monolithic.
The simplest type of monolithic iron concrete floor is smooth single-span slab. This type of floor, which has a thickness of 60...100 mm depending on the load and span, is used for rooms with side sizes up to 3 m.
For large spans they arrange beam floors, which can be:
■ teams and
■ monolithic.
So, if it is necessary to cover a room measuring 8 x 18 m (Fig. 6.4), beams with a span of 8 m with a step of 6 m are installed.
Rice. 6.4. Reinforced concrete monolithic ribbed covering: 1 - main beam, 2 - secondary beam, 3 - slab.
These beams are called main. Along them, after 1.5...2 m, they arrange the so-called secondary beams, having a span of 6 m. A slab with a thickness of 60... 100 mm is laid on top. Thus, the floor structure is ribbed. The height of the main beam can be approximately taken as 1/12...1/16 of the span, and the width as 1/8...1/12 of the distance between the axes. In ribbed floors, 50...70% of the concrete is spent on the slab. If this type of ceiling is made monolithic, then it is necessary to install formwork in a short time, carry out reinforcement works and laying concrete. This is one of the disadvantages of this type of overlap.
If the height of the main and secondary beams is assumed to be the same, then this type of floor is called caisson(Fig. 6.5).
Rice. 6.5. General form reinforced concrete monolithic coffered ceiling.
Their use is mainly related to the requirements of solving the interior of the room.
Prefabricated reinforced concrete ribbed floors are much more economical than monolithic ones, as they make it possible to increase the industrialism of construction, reduce labor costs and the time required for construction and installation work. An important requirement for installing prefabricated floors is to reduce the number of mounting elements. The best option is used when room-sized slabs are used.
A special kind A beam reinforced concrete floor is an overlap on beams placed in one direction with a pitch of 600... 1000 mm, and the filling between them is made of gypsum or lightweight concrete slabs, reinforced with wooden beam frames (for interfloor floors) or welded steel mesh (for attic floors).
Often, instead of rolling, double-hollow liner stones with a height of 250 mm and a length of 195 mm are also used. The gaps between stones and beams are carefully sealed cement mortar, which helps to increase the rigidity of the floor and sound insulation.
Elements of beam floors have a relatively small mass, and therefore they are used in the construction of buildings equipped with light-duty cranes.
Beamless monolithic reinforced concrete floors(Fig. 6.6.4) are a slab 150...200 mm thick, resting directly on columns, in the upper part of which there are thickenings called capitals.
Rice. 6.6.4. Reinforced concrete monolithic beamless floor:
a - general view, b - diagram of supporting the slab on the column, 1 - slab, 2 - capital, 3 - column.
The grid of columns for a beamless floor is assumed to be square or close to square with a side size of 5...6 m. The arrangement of prefabricated beamless floors is very effective.
The most widespread in civil engineering are slab floors. The main load-bearing elements of slab floors are different kinds reinforced concrete decking panels made from concrete.
Depending on the design schemes of buildings, they are (Fig. 6.7):
■ from panels resting with their ends on longitudinal load-bearing walls or on purlins laid along the building;
■ from panels resting with their ends on transverse walls or purlins laid across the building;
■ from panels supported on load-bearing walls or purlins on three or four sides;
■ from panels supported at four corners by frame columns.
Rice. 6.7. Structural diagrams of slab floors:
a - with longitudinal lines of supports, b - with transverse lines of supports, c - with support on three or four sides (along the contour), d - with support on four points (corners), 1 - floor panels resting on load-bearing walls, 2 - internal longitudinal or transverse load-bearing wall, 3 - external load-bearing wall, 4 - floor panel supported by purlins, 5 - purlins, 6 - columns, 7 - room-sized floor panel supported by columns, 8 - external non-load-bearing wall.
Minimum depth of decking in brick walls 120 mm, in block and panel - 100 mm on each side.
Precast concrete floor slabs during their installation, they are rigidly embedded in the walls using anchors and fastened together with welded or reinforced ties. The seams between the slabs are sealed with mortar. Thus, fairly rigid horizontal disks are obtained, increasing the overall stability of buildings.
Floor slabs are:
■ solid section,
■ ribbed (Fig. 6.8) and
■ hollow (Fig. 6.9).
Rice. 6.8. Prefabricated reinforced concrete panels ceilings: a - solid single-layer, b - solid two-layer, c - often ribbed with ribs up, d - often ribbed from two vibro-rolled shells, d - tent with ribs along the contour, 1,2 - mounting loops.
Rice. 6.9. Hollow-core floor panels: a - with round voids, b - panels produced on installations with concreting combines, c - panels with oval voids, 1 - upper layer, 2 - middle layer, 3 - bottom layer.
Solid single-layer panels represent reinforced concrete slab constant cross-section with a lower surface ready for painting and a flat upper surface prepared for flooring, have a thickness of 100... 120 mm with a multi-layer floor structure and 140 mm with a sticker on a linoleum slab on an elastic basis. For spans of more than 6 m, single-layer solid prestressed slabs with a thickness of 140 mm are used, in which sound insulation from airborne noise provided by the mass of the slab itself.
Also used laminated solid panels(see Fig. 6.8, b), which is a reinforced concrete slab of constant cross-section, the bottom layer of which is made of durable concrete, where tensile reinforcement is located, and the top layer is made of lighter and less durable concrete. These plates can also be three-layer.
Ribbed panels can be with ribs located both down and up. When the ribs are positioned upward, it is advisable to assemble the slab and floor structure at the factory, which increases the prefabrication factor and reduces labor costs on the construction site.
To increase the soundproofing ability of floors, layered structures are used, in which clean floors are arranged over soundproofing layers.
In Fig. 6.10, a - e show diagrams of layered floors.
Rice. 6.10. Structural schemes of floors: a - with a layered floor covering, b - with a separate floor, c - with a separate ceiling, d - a separate floor consisting of two load-bearing panels, e - with a separate ceiling and a layered floor covering, 1 - load-bearing floor panel, 2 - warm soundproofing layered floor, 3 - floor covering, 4 - separate floor base panel, 5 - separate ceiling panel, b - load-bearing floor panel.
Thus, the installation of an air gap (Fig. 6.10, d) with a thickness of 80... 100 mm, located between two load-bearing panels or between the load-bearing part of the floor and the structure of the acoustic ceiling (Fig. 6.10, c, e) or floor (Fig. 6.10, b), allows you to provide the necessary soundproofing ability of the ceiling. For this purpose, ceilings made of panels with ribs down and a separate ceiling are used.
Frequently ribbed ones are effective in this regard. panels, consisting from two vibro-rolled shells(see Fig. 6.8, d), one of which forms the base for the finished floor, and the other serves as the ceiling. A continuous air gap and soundproofing gaskets between the slabs provide the necessary sound insulation of the floor.
Hollow-core panels widely used for flooring. They are most often made from concrete classes B15 and B25 with a length of 2.4 to 6.4 m and a width of 0.8 to 2.4 m with a thickness of 220 mm.
Panels come with
■ round and
■ oval voids.
Slabs with oval voids are somewhat more economical in terms of concrete consumption, but are labor-intensive to manufacture. It must be borne in mind that the cost of hollow-core panels is relatively high.
Also used tent panels(see Fig. 6.8, d), which have the form of a slab framed along the contour with ribs facing down in the form of a cornice. Made to fit a room, they eliminate design diagram building crossbars and other beam elements, and due to their small thickness they allow you to reduce the height of the floor without reducing the height of the room.
When constructing public buildings, there is often a need to install floors with spans of 9, 12 and 15 m. For this, the following is used:
■ ribbed prestressed slabs 9 m long, 1.5 m wide and 0.4 m rib height (Fig. 6.11, a);
■ prestressed panels type TT-12 And TT-15 for spans of 12 and 15 m, respectively (Fig. 6.11, b, c).
Such slabs make it possible to increase the prefabrication of construction and reduce labor costs for constructing floors.
Rice. 6.11. Flooring slabs for spans of 9, 12 and 15 m: 1 - mounting loops, 2 - longitudinal ribs, 3 - transverse ribs.
Among the many structural elements In a private house, the ceiling is one of the most important and difficult components to design and install. This is where inexperienced builders make, perhaps, the most dangerous mistakes; it is about the arrangement of this system that the most questions are asked.
1. Why choose a tree
In any building, the ceiling is a horizontal structure that serves as the basis for creating the floor. In addition, being connected to the load-bearing walls of the house, it provides lateral stability to the structure, evenly distributing possible loads. Therefore, the highest demands are placed on the reliability of this design.
Regardless of what material is used in the construction of a house, wooden floors are most widespread in the private sector. They can often be seen in various stone cottages, and it is quite obvious that in wooden construction (logs, beams, frame and frame-panel technology) there is no alternative to such a solution. There are many objective reasons. Let's look at the advantages and disadvantages of wood floors.
In private low-rise construction, floors are installed in several options:
- Ready reinforced concrete slab,
- Monolithic reinforced concrete slab,
- Ready-made reinforced concrete beams,
- Beams and trusses made of rolled metal,
- Flooring made of lumber.
pros
Or why wooden floors are so popular.
- Small mass. By using boards or timber, we do not overload load-bearing walls and foundations. The weight of the ceiling is several times less than that of concrete or metal structures. Usually no technology is required.
- Minimum deadlines for completing work. Minimum labor intensity among all options.
- Versatility. Suitable for any building, in any environment.
- Possibility of installation at sub-zero and very high temperatures.
- No “wet” or dirty processes.
- Possibility of obtaining any level of thermal insulation and sound insulation characteristics.
- Possibility of using cavities for laying utilities (electrical network, heating, water supply, sewerage, low current...).
- The relatively low price of a prefabricated frame floor made of lumber, both in terms of the cost of parts/components and the contractor’s wages.
Minuses
The disadvantages of a wooden ceiling system made of wood are quite conventional.
- The difficulty of choosing the cross-section of materials and design solutions to ensure the calculated load-bearing capacity.
- The need to carry out additional fire prevention measures, as well as provide protection from moisture and pests (antiseptic treatment).
- The need to purchase soundproofing materials.
- Strict adherence to technology to avoid construction errors.
2. What material to use for assembly
Wooden flooring always consists of beams. But they can be made from a variety of lumber:
- Rounded log up to 30 cm in diameter.
- The beam is four-edged.
- Large section board (thickness from 50 mm, width up to 300 mm).
- Several boards of relatively small thickness, twisted face to face.
- I-beams, the upper and lower chords of which are made of edged planed boards/bars, and the vertical wall is made of OSB-3, plywood or profiled metal (wood-metal product).
- Closed boxes made of sheet materials(plywood, OSB).
- SIP panel. In essence, these are separate sections in which the beams are already sheathed and have an insulator inside.
- Various truss designs, allowing to cover large spans.
The easiest options for installation, as well as the cheapest and most convenient for subsequent operations, are those where the floor beams are made of edged lumber.
Due to the very high requirements for load-bearing capacity, durability and geometric deviations, first-grade lumber must be considered as blanks. It is possible to use products classified as second grade according to GOST, which do not have critical geometric deviations, defects and processing defects that can reduce strength characteristics and service life finished parts(through knots, twists, cross-layers, deep extended cracks...).
In these structures, the use of dead wood (dead wood, dead wood, burnt wood) is excluded due to insufficient strength and multiple damage to wood-destroying diseases and insects. It would also be a big mistake to buy a timber or board “with air”, “with Armenian size”, “TU” - due to the underestimated sections.
It must be exclusively healthy material from green spruce or pine, since needles, due to their resin content and the structure of the massif, withstand bending loads and compression much better than most hardwoods, and having a relatively low specific gravity.
Anyway edged lumber must be freed from remnants of bark and bast fibers, treated with an antiseptic and fire retardant. Dry planed lumber will perform best here, but material with natural humidity (up to 20 percent) during normal processing is also actively (and most importantly, effectively) used, especially since the price of edged timber or boards of this type is noticeably lower.
3. How to choose the size of beams and at what step to arrange them
The length of the beam is calculated in such a way that it covers the existing span and has a “margin” to provide support on load-bearing walls (read below for specific figures for permissible spans and wall penetration).
The cross-section of the board/beam is determined depending on the design loads that will be exerted on the floor during the operation of the building. These loads are divided into:
- Permanent.
- Temporary.
Temporary loads in a residential building include the weight of people and animals that can move along the floor, moving objects. Constant loads include the mass of the lumber of the structure itself (beams, joists), floor filling (insulation/noise insulation, insulating sheets), hemming (rolling), rough and finishing flooring, finishing flooring, partitions, as well as built-in communications, furniture, equipment and household items...
Also, you should not lose sight of the possibility of storing objects and materials, for example, when determining the load-bearing capacity of the floors of a non-residential cold attic, where unnecessary, rarely used things can be stored.
The sum of the dead and live loads is taken as a starting point, and a safety factor of 1.3 is usually applied to it. Exact figures (including the cross-section of lumber) must be determined by specialists in accordance with the provisions of SNiP 2.01.07-85 “Loads and Impacts”, but practice shows that the load values in private houses with wooden beams are approximately identical:
- For interfloor (including under a residential attic) and basement floors, the total load is about 350 - 400 kg/m2, where the share of the structure’s own weight is about 100 kilograms.
- For covering an unloaded attic - about 130 - 150 kg/m2.
- For covering a loaded non-residential attic up to 250 kg/m2.
It is obvious that unconditional safety is of paramount importance. Here a good margin is taken into account and the option is considered not so much of distributed loads on the entire floor (in such quantities they are practically unrealistic), but rather the possibility of a local load that can lead to deflections, which in turn caused:
- physiological discomfort of residents,
- destruction of components and materials,
- loss of aesthetic properties of the structure.
By the way, certain deflection values are allowed by regulatory documents. For residential premises, they can be no more than 1/350 of the span length (that is, 10 mm at 3 meters or 20 mm at six meters), but provided that the above limiting requirements are not violated.
When choosing the cross-section of lumber to create a beam, they are usually guided by the ratio of the width and thickness of the beam or board in the range of 1/1.5 - 1/4. Specific figures will depend, first of all, on: loads and span lengths. At independent design You can use data obtained from calculations using online calculators or publicly available tables.
Optimal average cross-section of wooden floor beams, mm
As we can see, to enlarge load-bearing capacity ceilings - it is enough to choose lumber with a larger width or greater thickness. It is also possible to assemble a beam from two boards, but in such a way that the resulting product has a cross-section no less than the calculated one. It should also be noted that the load-bearing properties and stability of a wooden floor increase if logs or various types of subfloors (sheet flooring made of plywood/OSB or edged boards) are used on top of the beams.
Another way to improve the strength properties of a wooden floor is to reduce the spacing of the beams. In their designs for private houses, engineers determine under different conditions the distance between beams from 300 mm to one and a half meters. IN frame construction The pitch of the beams is made dependent on the spacing of the posts, so that there is a post under the beam, and not just a horizontal frame run. Practice shows that the most appropriate from the point of view of practicality and cost of construction is a step of 600 or 1000 mm, since it is best suited for the subsequent installation of insulation and noise insulation by surprise (insulating materials have just such a form factor of plates and rolls). This distance also creates the optimal distance between the support points for installing floor joists installed perpendicular to the beams. The dependence of the cross section on the pitch is clearly visible from the numbers in the table.
Possible cross-section of floor beams when changing the pitch (total load on square meter about 400 kg)
4. How to properly install and secure beams
We have decided on the step - from 60 centimeters to a meter will be the golden mean. As for spans, it is best to limit yourself to 6 meters, ideally: four to five meters. Therefore, the designer always tries to “lay” the beams along the smaller side of the house/room. If the spans are too large (more than 6 meters), then they resort to installing load-bearing walls or support columns with crossbars inside the house. This approach makes it possible to use lumber of a smaller cross-section and increase the spacing, thereby reducing the weight of the floor and its cost for the customer with the same (or better) load-bearing characteristics. As an option, trusses are created from lighter lumber using metal perforated fasteners, for example, nail plates.
In any case, the beams are placed strictly horizontally, parallel to each other, maintaining the same pitch. On load-bearing walls and purlins wooden beam should rest at least 10 centimeters. As a rule, use 2/3 thickness outer wall from the side of the room (so that the end of the beam does not go out onto the street and remains protected from freezing). IN wooden walls they make a cut, in stone ones they leave openings during laying. In places where the beams of supporting structures touch, it is necessary to lay insulating materials: damping elastic pads made of rubber/felt, several layers of roofing felt as waterproofing, etc. Sometimes they use firing of sections of the beam that are subsequently hidden or coating them with bitumen mastics/primers.
Recently, special perforated brackets “beam holders/supports” have been increasingly used to create floors, which allow the beam to be mounted end-to-end with the wall. Using this type of brackets, units with transverse crossbars and beams truncated in length are also assembled (an opening for flight of stairs, chimney passage, etc.). The advantages of this solution are obvious:
- The resulting T-shaped connection is very reliable.
- The work is done quickly (there is no need to make cuts, it is much easier to set a single plane).
- No cold bridges are formed along the body of the beams, because the end is moving away from the street.
- It is possible to buy lumber of shorter length, since there is no need to insert the timber/board inside the wall.
In any case, it is very important, after adjusting the lumber to size, to thoroughly antisepticize the end of the beam.
5. What insulating layers should be used inside wooden floors
To answer this question, first of all, it is necessary to divide the overlapping structures (in a year-round habitable house) into three separate types:
- Basement ceiling,
- Interfloor,
- Attic.
In each specific case, the set of pie will be different.
Interfloor ceilings in the vast majority of cases separate rooms in which temperature regime similar or close in value (if there is room/floor/zone adjustment heating system). These also include the attic floor, which separates residential attic, since this room is heated, and the insulation is located inside roofing pie. For these reasons, thermal insulation is not needed here, but the issue of combating noise, airborne (voices, music...) and shock (steps, rearranging furniture...) becomes very relevant. As sound insulation, acoustic fibrous materials based on mineral wool are laid in the ceiling cavity, and sheets of sound-proofing membranes are also laid under the sheathing.
The basement design assumes that under the ceiling there is soil or a basement, cellar, or ground floor. Even if the room below is equipped for use, this type of floor requires full insulation, characteristic of the enclosing structures of a specific climate zone and a specific building with its unique thermal balance. According to standards, the average thickness for the Moscow region modern insulation with good thermal conductivity will be about 150-200 mm.
Similar thermal insulation requirements apply to the attic floor, which does not have a heated attic above it, because it will be the main barrier to heat loss through the roof of the building. By the way, due to the greater flow of heat through the upper part of the house, the thickness of the insulation here may be required more than in other places, for example, 200 mm instead of 150 or 250 mm instead of 200.
They use polystyrene foam, EPS, mineral wool with a density of 35 kg/m3 in slabs or cut into mats from a roll (one that is allowed for use in non-load-bearing areas is suitable). horizontal structures). Thermal insulation is laid between the beams, usually in several layers, with the joints bandaged. The load from the insulation is transferred to the beam through the rough hemming (often it is attached to the beams using cranial bars).
Where wadding insulation/sound insulation is used in structures, it should be protected from moisture. In the basement, moisture can rise in the form of evaporation from the ground or from the basement/cellar. Water vapor can enter interfloor ceilings and attics, which always saturates the air in residential premises during human activities. In both cases, underneath the insulation you need to lay construction material vapor barrier film, which can be ordinary or reinforced polyethylene. But, if thermal insulation is performed using extruded polystyrene foam, which does not have any significant level of water absorption, then a vapor barrier will not be needed.
On top, insulation and fibrous soundproofing materials are protected with waterproof sheets, which can be membranes or non-perforated waterproofing.
A reliable hydrobarrier is especially relevant in rooms with high humidity: kitchen, laundry, bathroom... In such places it is spread on top of the beams, always with the strips overlapping by 100-150 mm and gluing the seam. The canvases along the entire perimeter of the premises must be placed on the wall - to a height of at least 50 mm above the finishing coating.
It makes sense to supplement the ceiling, which will later be tiled, with a rough flooring made of waterproof sheet materials - various types cement-containing slabs, preferably tongue-and-groove. On such a continuous flooring you can carry out additional coating waterproofing, perform thin-layer leveling of the plane with a leveling compound or lay the tiles immediately.
You can choose another option - collect from edged boards continuous flooring, lay a hydraulic barrier, pour a thin-layer screed (up to 30 mm), install tiles.
There are also modern adhesives (and elastic grouts) that allow tiling wooden bases, including movable and heated ones. Therefore, tiled floors are often sold here on moisture-resistant plywood or OSB.
Important! Taking into account the increasing loads (general or local - a large bathtub, a Jacuzzi bowl, a floor-standing boiler...), the calculation of the cross-section and pitch of beams under such rooms must be performed individually.
If desired, floors in the bathroom or kitchen wooden house can be equipped with a heating cable or pipes of the water circuit of the heating system. They are mounted both in screeds and a layer of tile adhesive, and between joists in a deliberately created air gap. With any chosen option, the ceiling must be well insulated so as not to heat the ceiling of the room from below, preferably equipped with waterproofing with a reflective foil layer.
When building a private house, it is important to choose the right Constructive decisions its elements. One of the most important structures can be called overlap. Properly selected thickness of the reinforced concrete floor slab in the house between floors will ensure its reliability and safety.
Types of reinforced concrete structures and scope
Monolithic slabs are suitable for use in massive buildings made of stone or brick. IN brick house such an overlap creates a disk that gives the building additional rigidity. When laying interfloor reinforced concrete floors, it is important to choose the type of its manufacture:
- monolithic;
- prefabricated
Both of these methods are common today, but gradually the first one is replacing the second one. The main disadvantages of a monolithic floor are the cost of formwork and the need to wait for the concrete to harden. The advantages include:
- high laying speed;
- reduction of financial costs;
- no need for complex lifting equipment;
- possibility of pouring a slab of complex configuration in plan;
- reliability and durability.
The advantages of prefabricated technology include:
- high installation speed;
- there is no need to wait until the concrete gains strength;
- reliability and strength;
- more simple technology manufacturing.
This method has slightly more disadvantages than the previous one:
- large mass of individual elements;
- there is a need for lifting equipment (truck crane);
- limited number of standard sizes, difficulty in covering rooms of unusual shapes.
Scheme of a prefabricated product The choice between technologies for constructing floors between floors depends on the preferences of the future owner of the house and economic considerations. If the distances between load-bearing walls are far from standard, a large number of non-standard products will be required, which will lead to higher construction costs. In this case, it is better to opt for the monolithic version.
Slab thickness
It is necessary to know the thickness of the slab in order to calculate overall height ceilings and floors. This will be required when calculating the height of the floor, room and the entire building. The thickness of the overlap depends on the type of structure chosen. If the decision is made to use monolithic technology, it also depends on the loads from people, furniture, equipment and floor construction.
Prefabricated slabs according to the PC and PB series
These elements are most often used in construction. PC slabs are round-hollow. They are laid between floors, both in private houses and in multi-storey buildings. PB slabs are enough new technology, which is gradually replacing the PC series. They can be produced in any length, regardless of the dimensions given in regulatory documents. They differ in the manufacturing method - the continuous molding method. They have some limitations and are not fully studied, but they are successfully used in both private and mass construction.
Design diagram measuring 220 mm The thickness of the plate is standard. Is 220 mm. To calculate the total height of the floor with the floor structure, you need to add to this value:
- thickness concrete screed, approximately 30-50 mm;
- if necessary, sound insulation or insulation thickness thermal insulation material(30-50 mm for sound insulation, 100-150 mm for thermal insulation);
- flooring (depending on the type, the highest height will be for a wooden floor, the smallest for linoleum or ceramic tiles);
- ceiling design.
In total, the height of the concrete floor in a private house with a floor structure when using PB or PC series slabs is approximately 300 mm.
PT series plates
These elements are in most cases used as additional elements for the PB and PC series. The laying of such slabs between levels is carried out in those places where the distance between the walls does not allow the installation of large-sized products. They have small dimensions in plan, which allows them to cover small spans. The slabs are suitable for installation over corridors, bathrooms, utility rooms and storage rooms. Support can be done on all sides.
Reinforced concrete products for residential and public buildings Product thickness 80 or 120 mm. The total height of the reinforced concrete floor with floor elements is 150-200 mm, depending on the type of floor covering.
When used, align with PC and PB products along the upper edge of the floor.
Irregularities are corrected using the ceiling structure.
Overlapping according to profiled sheet
A fairly common method for private housing construction. In this case, the profiled sheet serves as formwork and load-bearing element monolithic slab. Main design elements:
Product design based on profiled sheets - load-bearing beams (I-beams, channels or angles with a large flange width);
- corrugated sheet, which is laid on the beams (the waves should be perpendicular to the load-bearing elements);
- layer of concrete mortar.
All thicknesses are selected depending on the payload. For a private house, you can give the average values of a monolithic slab between spaces located at different horizontal levels:
- The height of beams (I-beams or channels) for spans up to 5-6 meters is approximately 220-270 mm.
- The wave height of the corrugated sheet plus the thickness of the concrete layer depends on the step between load-bearing beams and planned load. The minimum value for a monolithic slab of a private house is 150 mm.
- Concrete screed, the thickness of which is 30-50 mm.
- If necessary, add a layer of insulation from 30 to 150 mm, depending on the purpose of its installation.
- Clean floor design. The thickness depends on the type of flooring.
Supporting a profiled sheet can occur in two ways:
- on top of supporting beams;
- adjacent to them.
In the first case, the thickness takes into account the full height of the I-beam or channel, and in the second, the thickness of the reinforced concrete floor is significantly reduced. The minimum height is for light loads.
By regulatory documents, the weight that falls on the floors in a private house is 150 kg per square meter.
When calculating, this value must be increased by a safety factor of 1.2. For more severe loads, reinforced corrugated sheets and a thicker concrete layer are used.
Ribbed monolithic ceiling
For a private home, you can use another technology for making a floor base. Ribbed reinforced concrete slab consists of long ribs spread along the long sides of the room and a thin layer of concrete between them. The space between the ribs is filled with insulation (expanded clay, mineral wool, expanded polystyrene, etc.).
The thickness of the monolithic slab is calculated from the following values:
- Rib height. For private housing construction, in most cases a thickness of 200 mm is sufficient. In this case, the thickness of the area between the ribs can be 50-100 mm. The rib width is selected to be approximately 100 mm.
- Thickness cement-sand screed . Accepted within 30-50 mm.
- Floor construction. The thickness depends on the floor covering and on average is in the range of 10-50 mm.
A ribbed ceiling, as well as a corrugated sheet, allows you to reduce concrete consumption while maintaining a sufficiently large thickness. Making ribs – difficult task. The use of corrugated sheets allows you to create a floor with a ribbed surface without unnecessary labor costs.
Proper selection and calculation of the thickness of a concrete slab will allow you to calculate the height of the premises, the consumption of concrete mixture and determine the financial and labor costs at the design stage of the facility. In the case of prefabricated floors, the thickness for all elements is standard.
The floors are solid reinforced concrete structures. Their use is relevant for increased weight loads, primarily in multi-storey buildings. In private construction, their main advantages include the ability to reduce installation costs by independently performing individual or all stages of work with minimal use of special equipment. The technology is considered labor-intensive; to avoid errors, the calculation of the slab should be entrusted to specialists. The obtained parameters must be taken into account when preparing the main house project.
Conventionally, all are divided into prefabricated (solid or hollow, manufactured at a factory), frequently ribbed (cellular type with sections of lightweight material or empty blocks) and monolithic. The latter are valued primarily for the absence of seams; this option is chosen when concreting multi-storey buildings, pouring floors or demarcating floors in individual buildings. Depending on the design and installation methods are divided into: beam, beamless (the most popular type in the construction of private houses with smooth surface), With permanent formwork(at the same time acts as a heat-insulating layer) and laid on a steel flooring. The latter are valued for their reduced labor intensity and the ability to reduce thickness and weight.
Features and advantages of monolithic flooring
The advantages include:
1. Strength and solidity (no seams), and, as a result, ensuring a uniform load on the foundation and load-bearing walls.
2. Possibility of support on columns. This gives more freedom in the planning process compared to the option of laying prefabricated floor slabs from ready-made factory elements of a standard size.
3. Safe arrangement of a balcony without the need for additional supports due to the monolithic nature of the main horizontal structure.
Calculation of the slab, drawing up a reinforcement diagram
Ideally, the design is entrusted to specialists; they will help you choose an option with correctly distributed loads, optimal in terms of “reliability-cost of building materials.” The initial data for independent calculations are the dimensions of the floor with mandatory consideration of the width of the support areas. The thickness of the monolith is selected based on the maximum length of the longitudinal span (the recommended ratio for beamless structures is 1:30, but not less than 15 cm). For floors within 6 m, the minimum is 20 cm; above 6, options with reinforcement with stiffening ribs are considered. In beam-type varieties, the pitch of the supports is taken into account (accordingly, the minimum height is found by dividing it by 30).
The calculation of the slab begins with determining its own weight: the average (2500 kg/m3) is multiplied by the thickness of the floor. The standard temporary load (weight of furniture, equipment and people) for residential buildings is 150 kg/m2, taking into account the 30% reserve it is increased to 195-200. The total, maximum possible load is obtained by adding these values.
To check the cross-section of the reinforcement, the maximum bending moment is calculated, the formula depends on the method of weight distribution. For a standard beamless floor supported on two load-bearing walls M max = (q·l2)/ 8, where q is the total load, kg/cm2, l2 is the span width. This formula is the simplest; in the absence of reinforcement in areas of maximum concrete compression or uneven weight distribution, it becomes more complicated.
To check the cross-section of the reinforcement, a coefficient is calculated that takes into account the design resistance of building materials (reference values depend on the selected mortar strength class and steel grade). The resulting value corresponds to the minimum permissible area of metal in a cross-section of the slab. It is compared with the preliminary one; if it is exceeded, strengthening of the circuit is required (reducing the cell pitch or using rods with a larger diameter).
Due to the complexity, the calculation is usually entrusted to specialists; when it is done, a checkerboard pattern of two grids (lower and upper) with a cell pitch of 20x20 cm and a rod thickness of 10-14 mm (hot-rolled steel) is selected. Provision is made for both reinforcement in the center of the monolithic slab, areas with increased loads and places of contact with supports, as well as a margin for the overlap of the floor on the walls (depending on the strength of the building materials - from 150 mm for brick to 250 for cellular concrete). If possible, longitudinal and transverse rods are laid unbroken; if this condition is violated, they overlap - at least 40 cm.
Main stages of installation
Laying begins with the calculation and purchase of building materials (ideally, project data is used). Formwork structures are prepared: panels made of thick moisture-resistant plywood, metal or plastic, beams and telescopic supports (1 piece/m2), equipment for preparing, feeding and compacting concrete, tools for bending reinforcement and special stands. If necessary, an armored belt is laid around the perimeter of the load-bearing walls; such a need arises when constructing floors in a house made of aerated concrete.
Key steps include:
- Assembly and installation of formwork.
- Placement of reinforced frame.
- Pouring a monolithic slab with concrete, compacting and leveling.
- Humidity maintenance of the solution, covering, dismantling of the formwork after 28 days.
1. Requirements for supports and shields.
Installation involves pouring concrete into a sealed horizontal formwork; preference is given to special prefabricated structures. In principle, it is not difficult to make panels yourself from plywood with a thickness of at least 20 mm (it is better not to use boards due to difficulties in fitting). Required condition is the installation of telescopic metal racks(when constructing the ceiling of the first floor of the house, they are replaced by stationary supports). If they are absent, replacement with logs with a diameter of at least 8 cm is allowed, but you should be prepared for problems when adjusting the level.
To support the panels, a crossbar is laid - a longitudinal beam with a cross-section of at least 10x10 cm; if necessary, the formwork is reinforced with transverse elements (this situation most often arises when working with homemade products). The boards are laid without gaps, the edges rest tightly against the wall. When installing vertical structures, the amount of overlap on the supporting systems is taken into account. To eliminate the risk of leakage, the bottom is covered with film; sealed factory reusable varieties are lubricated to facilitate the removal process. The stage ends with a level check; deviations are unacceptable.
2. What needs to be taken into account when reinforcing?
Metal reinforcement is the main requirement of the technology. The distance from the edge of the concrete to the metal is at least 25 mm. The joints are tied with wire with a cross-section of 1.2-1.5 mm; welding is not allowed. To install the meshes, pre-prepared clamps are used: made of steel with a thickness of at least 10 mm, with an interval of up to 1 m, similar elements are placed at the ends. Reinforcement of a monolithic reinforced concrete floor is completed by laying connectors that ensure uniform load transfer on the entire system - after 40 cm near the walls, after 70 from it, with a subsequent step of 20.
3. The nuances of concreting.
The main requirement of the technology is process continuity; ideally, the solution is ordered at factories and poured using appropriate equipment. The recommended thickness of the concrete layer is 20 cm, which in most cases coincides with the height of the ceiling itself. The minimum grade is M200; in order to enhance the thermal insulation properties and lighten the weight, part of the coarse high-strength filler can be replaced with expanded clay, but this method requires approval by specialists (strength testing).
Holes for supplying communications and ventilation ducts laid before the start of pouring, drilling a frozen monolithic slab is considered a violation. The stage ends with the mandatory compaction of concrete using deep vibrators. The rules for caring for the surface are generally standard, but you cannot water the structure abundantly; unlike the foundation or vertical walls, it is wetted more carefully.
Prices
The cost of pouring when contacting professional companies varies from 4,000 to 9,000 rubles/m3 (provided that the customer’s formwork is used). The final cost depends on the chosen reinforcement scheme, the height of the future slab (from the ground level or from the level of the previous horizontal support) and its thickness, the method of placement (on columns or load-bearing walls), and the total scope of work. The list of services provided by construction companies includes installation and dismantling of formwork structures, assembly of reinforced frames according to a project prepared in advance (paid separately), continuous concreting and maintenance of the laid mixture: watering, covering, and, if necessary, heating. The advantage of turning to professionals is the mandatory quality control carried out upon completion of the curing process.
The advantages of laying the floor with your own hands include a reduction in the cost of paying for work - up to 30% at least. For pouring, simple building materials are used - concrete and reinforcement; saving on them is unacceptable. The volume of the solution is calculated based on the thickness and area of the slab, the length and weight of the metal is calculated according to a reinforcement scheme drawn up in advance. Renting formwork structures is expensive: the minimum price per m2 is 400 rubles per month (it cannot be removed earlier).
Additional costs when doing the work yourself include the need for special equipment and containers for lifting the solution to the top (shoe buckets and a crane or concrete pump). This is not a problem when installing solid floors on ground floors at home, but in other cases it is impossible to do without the appropriate equipment. This is explained by the main requirement of the technology - a continuous concreting process, monolithic floors with individual patches frozen in different days, are inferior in quality to those poured at once. Minimum costs when performing all stages independently, they amount to 3,200 rubles per 1 m2 with a slab thickness of 20 cm.
01.01.2011
| We will consider the assessment of the final costs for installing the floor of the first floor using the example of a selected house with a total area of 167.0 m2. Floor area of the first floor – 88.9 m2, area interfloor ceilings- 78.1 m2. The comparative assessment was carried out taking into account: I will immediately present the results of the calculations obtained. The cost of installing the floor of the first floor in the option of using precast reinforced concrete was The cost of installing the floor of the first floor in the case of using monolithic reinforced concrete was Costs for installing the floor of the first floor in the compacted soil version Costs for installing the floor of the first floor in the application option wooden beam will amount to Costs for installing the floor of the first floor in the option of using biopositive I-beams will amount to The cost of installing the floor of the first floor in the case of using beams from LVL timber will be |
|
Material |
Quantity per m2 |
Price with shipping** |
Amount (RUB) |
| PNO floor slabs |
850.00 RUR/m2 | ||
| Masonry mortar |
RUB 2,654.00/t | ||
| Mortar for sealing slab joints |
RUB 2,654.00/t | ||
| Wire for connecting the plates together |
1.0584 linear meters |
10.00 RUR/linear meter |
