The support of the slab overlap on the wall is one of the indicators of reliability, safety and long life of the building. Much depends on the proper installation of the plates, so all the rules and regulations are regulated by state bodies. There is a special document - SNiP, which has compiled a set of these standards.
Purpose of overlappings
Reinforced concrete slabs are one of the main load-bearing structures of the building, so they are given enough attention during construction. The main function of reinforced concrete floors is the transfer and distribution of the load to its own weight, and then to other elements of the building.
At the location, these building structures are divided into interfloor, basement and attic. Plates are manufactured in the factory and are of several types:
- prefabricated monolithic;
- multihollow;
- made of heavy concrete grades.
The main requirements that high-quality ceilings should have are considered strength, stiffness, fireproof, sound and water tightness.
Most floor slabs are made with voids, this design is considered the most optimal in terms of weight and quality. Laying takes place on the bearing walls of the building, the pitch of which can be up to 9 m.
Parameters for the amount of support
The maximum and minimum bearing of the slab on the wall is determined by the following factors:
- The purpose of the building is residential, industrial, administrative.
- The material from which the bearing walls are made and their thickness.
- The size of the overlapping span between the walls.
- The size of the reinforced concrete slab and its weight.
- Future floor loads.
- Seismic indicators of the location of the building.
According to SNiP, the support of floor slabs on the walls is from 9 to 12 cm, depending on the factors described above. The final size is determined by the engineers when designing the building. It is important to correctly calculate the size of the overlap, otherwise the pressure of the floors can lead to the gradual cracking and destruction of the building.
Knot supporting a plate on a brick wall
During the construction of buildings made of brick, masonry is carried out right up to the future ceiling, while it is important to leave small niches for the installation of ceilings. The node supporting the floor slab on the wall is created taking into account the following conditions:
- the ends of the plates should not rest on the brickwork. For example, with an overlap of 12 cm, the width of the niche should be 13 cm;
- the composition of the mortar for laying and fixing the floors should be identical;
- voids formed in the channels should be filled with concrete inserts. They are manufactured at the factory along with the plates.
The minimum support of floor slabs on a brick wall is not standardized if the reinforced concrete product rests on one side on the end walls. Installation is carried out so that the masonry, which will be above the ceiling, does not lie on the formed extreme voids.
Installation of floors
The installation of floors is carried out by a team of four-person builders:
- crane operator who feeds the stove,
- slab rigger
- two installers involved in coordinating the plate and placing it in a given place.
Supporting floor slabs on a brick wall is one of the most important procedures requiring strict adherence to standards.
Before carrying out installation work, it is necessary to level the comb of the brickwork. If this is not done, the stove will be unstable. The gaps between the slabs are sealed with cement mortar.
Features of the installation of ceilings for buildings made of aerated concrete
The ceiling slab is supported on the wall by an annular reinforced belt, which is mounted around its perimeter. Such a monolithic concrete tape covering the entire building is mandatory if the bearing size is less than 12 cm. The following parameters are recommended for the arm belt:
- thickness 12 cm;
- width 25 cm;
- the depth of support is the same as for reinforced concrete floors.
In combination with strong reinforced concrete slabs, the reinforced belt creates a rigid structure, which provides sufficient resistance to the building against accidental effects, temperature changes and shrinkage deformations.
If the amount of support of the ceiling on the wall is more than 12 cm, then the building does not need an additional reinforced belt. In such cases, it is enough to build a reinforced belt from a ring anchor along the outer perimeter of the plates.
Calculation of the bearing parameter
It regulates the amount of support of floor slabs on the walls of SNiP (otherwise, a set of norms and rules), highlighting the following types of plate sizes:
- modular - the span width into which the structure is installed;
- constructive - the actual size of the ceiling plate from one end to the other.
For example, if the modular floor length is 6.0 m, then the real one is 5.98 m. To obtain a room size of 5.7 m, a slab with a support of 12 cm should be installed. The optimal calculation of the support of the floor slab on the wall is also important for maintaining warmth in the room. If the end face is too close to the outer surface of the wall, penetration of cold air inside will be observed. This design gives a cold floor in the winter.
Basement floor
Installation of floor slabs for the basement is the simplest. In order to achieve a flat surface for laying reinforced concrete structures, the upper edge of the foundation should be leveled. Then on the upper edge of the flooded foundation exposed formwork boards. This design is poured with concrete mortar. Thus, a perfectly flat cushion is obtained for the installation of plates.
Plates installed on a smooth surface form an even ceiling, in which it is only necessary to close the seams, after which it is ready for decoration.
Sealing joints between floors
After the optimal size of the support of the floor slabs on the walls has been determined, and the reinforced concrete structures themselves have been installed, you should start sealing the joints between them.
For this, a sand-cement mortar is used if the gaps are insignificant. If there are large gaps, you should use the following methods:
- Formwork is arranged from wooden boards, into which subsequent pouring of the mortar takes place.
- Large slots can be covered with fragments of reinforcement, fragments of bricks and other materials. They are rammed into slots, which are then coated with concrete mortar.
It is important to close up the voids formed during the installation of the boards immediately. This greatly simplifies the finishing work that will be done at the end of construction.
The future strength and durability of the structure depend on the correct calculation of the amount of support of the floor to the wall. Therefore, this process is governed by SNiP rules and is carried out by experienced designers.