There are several types of ceilings that are used during the construction of buildings and structures. They have certain advantages and disadvantages. One of the spectacular varieties is the caisson floor. It is used less often than monolithic plates. But at the same time he has a lot of advantages. What constitutes a caisson type overlap will be considered below.
general description
Many people do not know what kind of overlap is called caisson. This is not the most common type of ceiling. Today, meeting a building project with such an overlap is difficult. This is what attracts many builders. The interior using this technology is original.
Any overlap is an important building element. It is responsible for the safety and reliability of the structure, therefore it must comply with the established requirements. The caisson floor has been known to mankind for a long time. Even in ancient Rome, a similar technology was used in construction. Since then, the ceiling of the presented variety has established itself on the positive side.
In our country, such overlappings are rarely used so far, but they are actively used in buildings of other countries. It consists of beams that are directed towards each other at an angle (not necessarily straight). This approach allows you to create a lightweight design. It has an original appearance and can be used in the arrangement of various buildings.
You can mount the caisson type ceiling yourself. Today, many special devices and structural elements are on sale for this. This greatly facilitates the work of the wizard. You can purchase everything you need in a hardware store and do it yourself.
Historical reference
Coffered floors (photos are presented in the review) are widespread in the architecture of Ancient Rome and Greece. Between the intersections of the beams installed flooring. They were decorated with paintings or sculptural elements.
Previously, the overlapping type was constructed of wood. Such designs were also used in other countries, for example, in Ancient Egypt. Ceilings of this type were found on murals and ancient mosaics.
A caisson monolithic reinforced concrete floor was a real breakthrough in the field of architecture and construction. This material has been used in Russia since 1861. Most often, floors and columns were built from it.
The first building with caisson floors made of reinforced concrete was built in 1934. It was the building of the Center Union (architect Le Corbusier). The ribs at this overlap were directed upwards. The design was made using monolithic technology.
More often, the technology presented is used in construction in foreign countries. So, for example, such buildings have long won the attention of builders in Spain, Germany, England, Italy, etc. Most often, such structures have been used and are now used in the construction of administrative buildings.
Key Features
A caisson monolithic floor is created from panels that are mounted on corner bearing columns. Such plates look like ribs or beams intersecting at right angles. Using a thin layer of concrete, they are combined into a single system. This results in a ceiling that resembles a waffle in appearance.
Most often, the plate has a square shape, but may have a different configuration, for example, domed.
It is worth noting that conventional monolithic ceilings involve the fastening of plates through beams. These are the bearing parts of the structure. Caisson types of floors have special ribs. They assume the function of beams. Ribs in a caisson construction have a pitch of not more than 1.5 m. They form a structure in the form of a grid. This allows you to redistribute the load. The design becomes stronger because of this. This allows you to reduce the thickness of the layer of monolithic plates to 5-8 cm.
To ensure greater reliability, reinforcement of caisson floors is carried out. Plates have a thickness of 25-45 cm. The height of the ribs that protrude above the base reaches 20-40 cm. In this case, the proportion established by building codes and rules must be maintained. The height of the rib should not be less than 1/20 of the span. The sizes of the caisson floor can be different. The largest of them reach dimensions of 35x35 m.
Plates can be supported by supporting columns or walls. In the first version you need 4 supports. The columns will hold the structure in the corners.
Benefits
There are many advantages to floor slabs. This provides the increasing popularity of the type of construction projects presented. In caisson ceilings, the ribs are the basis. Due to their presence, it turns out to reduce cement consumption by 2 times, and reinforcement by 3 times, compared with a conventional reinforced concrete slab of similar strength.
This feature allows you to expand opportunities when designing the thickness of the ceiling. Also, its shape can be very original. The configuration can be almost any. You can even create a dome or arched structure.
Now the technology with the distance between the supports for the slab from 10 to 34 m has been developed and is being applied. At the same time, less load is applied to the walls or columns. This is due to a decrease in overlap weight. This, in turn, leads to a reduction in the total loads that act on the foundation.
Another positive feature is the fact that the caisson floor slab is resistant to vibrations caused by an earthquake. In areas of increased seismic hazard, their use is allowed in the presence of a span of more than 6 m.
Ribbed varieties of designs are distinguished by a 2-3 times greater load-bearing capacity. The thickness in this case can be 2 times less than with the arrangement of ordinary smooth ceilings. The load-bearing elements will need to be mounted less, which speeds up the construction process. Material consumption of construction is also reduced. Construction costs are markedly reduced. In some cases, this figure reaches 3 times.
Application area
Caisson flooring is used in various types of construction. Most often, this type of structure is used in loaded engineering structures. Also, most often they are installed in buildings with a large number of people. It can be shopping, entertainment or sports complexes, cinemas or theaters, educational institutions, etc.
It is worth noting that in large cities of our country, large-scale industries are transferred outside the city limits. Large buildings remain from them, which are sometimes even impractical, from an economic point of view, to demolish. Therefore, such facilities are converted, turning them into multifunctional centers. This creates additional overlap. Most often they are made precisely by the caisson technology.
If you want to equip the production building with bridge cranes, you must also use additional ceilings. The height of such complexes can exceed 10 m. To ensure its proper functioning, caisson varieties of ceilings are created. They are optimal in such conditions in all respects.
The scope of the presented designs is not limited to industrial construction. In private homes, the presented technology can also be applied. This allows you to reduce costs, as well as make the original ceiling.
Varieties
The caisson floor according to the manufacturing technology is of two types. These are monolithic and precast-monolithic varieties of designs. They have characteristic differences.
So, precast-monolithic ceilings consist of hollow prefabricated blocks. Their sizes are 20x20x60 cm and 30x30x80 cm. They are in sections of a stretched type, in compressed sections of a monolithic slab. Blocks in this case are mounted in the form of a figure closed on all sides. The caisson formwork of the floors in this case is non-removable, consists of beams that remain in the concrete body. The thickness of the monolithic concrete layer above the beams should be 5-6 cm. In places where the structure is connected to the supports, the slab is continuous, since tensile loads act on it in these places. Block and reinforce on top.
Monolithic types of floors of the presented type are distinguished by an optimal indicator of the distribution of cement. There is no excess material between the ribs. This significantly reduces the weight of the structure. It has a ribbed structure. In stretched sections, the mixture is not stacked. Only the ribs are concreted here. They are reinforced, which increases tensile strength. This variety of ceilings can significantly save on materials. Overlapping spans may be increased.
Equipment
Before starting construction work, it is necessary to calculate the caisson floor. It is created in accordance with PPR according to working drawings. To perform the work, it will be necessary to prepare the necessary equipment and materials. The amount of cement and reinforcement depends on the area of the room. For the correct calculation, prepared drawings are used.
In the course of work, you will need a grinder, an electric drill, as well as a nozzle in the form of a construction mixer. Cement mortar can be purchased ready-made or made independently using a concrete mixer. The first option is simpler, therefore preferable. But to make the mixture yourself will be cheaper.
You need to prepare a set of wrenches, a screwdriver and screwdrivers. A chisel and trowel are also useful. When working, builders use a spatula, pliers and a hacksaw (including metal). Measurement is carried out using a tape measure and a pencil. You will also need a plumb line and a building level. Having prepared everything you need, you can begin to work. It is performed using special technology.
Formwork preparation
Builders recommend making do-it-yourself caisson ceilings directly on the spot. Formwork must be special, removable type. In total, 3 of their varieties are suitable for this:
- Standard system type Skydome. It includes plastic elements that make it easy to remove the formwork after hardening concrete. Its surfaces repel the solution, so it does not stick to the surfaces of the form. Such formwork is reusable. They also include rails and racks for installation.
- Combined formwork. For this, a temporary plywood flooring is made. Subsequently, elements of conventional formwork are installed on it.
- The mold is made of wood flooring, as well as home-made formwork from plywood. This is most often a disposable design. It can even be made of cardboard coated with a layer of polyethylene.
Pouring concrete
Concrete is poured into prepared forms in two stages. The fittings must be mounted so that it is correctly positioned inside the formwork. Its fixation must be strong so that it does not move during pouring.
Next, install special clamps. Reinforcement also needs to be mounted in two steps. First, it is laid in the ribs. The upper reinforcement has not yet been laid. In this case, clamps are used. When the first batch of concrete is poured (this allows the formation of ribs), you can mount the subsequent frame of metal reinforcement. It has lower and upper longitudinal elements, which are fixed with clamps.
Overlapping should be strong enough. The aggregate in the concrete mixture should be fine-grained or ordinary. Strength class must not be lower than B15. Porous concrete with strength class B12.5 can be used. The water-cement ratio should have an index of 0.5. Filling is carried out according to standard methods.
Using a needle-type vibrator, the mass is compacted in the formwork. The tool must be inserted into concrete vertically or at a slight slope.
Wood ceiling
Many modern designers today adopt the presented methodology. As a result, a ceiling is created from ribs intersecting each other. They create a grid on the ceiling. A thin layer combines all the structural elements together. For such a ceiling, the supporting qualities are secondary. It should be light and aesthetic.
The ceiling of the presented type has three main structural elements. These are ribs (beams) that provide rigidity, a base and decorative elements. As the latter, curbs, cornices, patterns, etc. are actively used.
Coffered ceilings can be made not only of wood, but also of plastic. The base is most often made of chipboard, sheets of polyurethane, drywall or plywood. Decorative elements cast from plaster look spectacular. In the cells, spotlights look good. The ribs may have a different configuration. This provides different effects of light scattering. This design looks interesting in different styles of interior.