Under suburban and high-rise buildings, foundations of various types can be erected. For example, in some cases, solid slab foundations are poured under houses. Such bases, in turn, can also be classified into several types. Before starting to pour a solid foundation, of course, its draft is made without fail.
Need to apply
Slab foundations are one of the most reliable types of house foundations. Tape and columnar in this regard, they are superior in any case. However, the area of this type of structure is very large. They are solid foundations, a solid thick slab under the whole house.
The construction of such structures, of course, is very expensive. In addition, for example, during the construction of a low-rise country house, foundations of this type, unlike others, cannot be poured with concrete using artisanal means. In this case, the cement mortar has to be ordered ready-made. Pouring liquid concrete into the formworkerecting such a foundation from a tank using a hose. And this, of course, makes the construction of the foundation even more expensive.
Because of the high cost, foundations are erected with a solid slab under the houses quite rarely. Their construction is generally considered expedient only when the building is being built on non-static soils. In this case, a solid slab can maintain the integrity of other building structures when moving.
Also, foundations of this type can be erected under various kinds of buildings of a small area. For example, sometimes garden gazebos are built on such a foundation. Most often, under such structures, of course, columnar foundations are built. A solid foundation, however, in this case can also be a good solution.
The stove under the gazebo or small outbuilding, of course, will be very small. With a small depth of concrete, it will not take much. In addition, it will be possible to pour the slab under the gazebo without the use of special equipment with assistants - manually at a time.
Main types by filling method
During the construction of houses, solid foundations can be erected:
- unburied;
- shallow;
- very deep.
The first type of base can only be used in areas where there is no frost heaving. They build exceptionally light houses of a small area on non-buried foundations. The thickness of such structures, depending on the type of soil, canfluctuate within 30-50 cm. Sometimes heavy brick houses are also erected on such foundations. But the use of non-buried base slabs under such structures is allowed only on rocky soils.
Shallow foundations are usually erected during the construction of small private houses. The pit under them is dug very shallow. In most cases, when pouring such a base on the site, the top fertile soil layer is simply removed according to the marking. Deep foundations are built only on heaving soils under heavy buildings.
Types by design
In this regard, solid foundations are distinguished:
- monolithic;
- lattice.
The first type of base is a conventional concrete slab. Solid monolithic foundations are the simplest and most popular type of such structures. But on very unreliable soils, foundations with stiffeners can also be equipped. The latter are poured directly under the stove.
Sometimes the edges of the lattice bases can be directed upwards. In this case, the walls of the building are erected on them using approximately the same technology as on strip foundations. When using this type of solid base in the building, among other things, it is possible to equip a basement. It is in this way that, for example, heavily buried slab foundations are often poured.
Design
When developing drawings of a solid foundation, of course, in the first placeshould determine its thickness. When building high-rise city buildings, such calculations are made exclusively by specialists using various formulas.
In individual construction, a reinforced concrete solid foundation project for a small house can be developed independently. In this case, most likely, you don’t even have to calculate anything. There are standard indicators of the thickness of such bases for certain types of buildings, which can be guided in the process of drafting a project.
So, for example:
- arbors and light outbuildings are erected on solid foundations 100-150 mm thick;
- under light frame private houses, as well as one-story log and block houses, foundations of this type are most often poured by 200-300 mm;
-
solid foundations 250-350 mm thick are erected under concrete structures or buildings made of brick or two-story chopped;
- under two- or three-story houses made of brick or concrete, it is supposed to fill slab bases by 300-400 mm.
Load collection
If you wish, of course, you can independently make a more accurate calculation of a solid foundation when building a country house. The collection of loads during pouring of such a structure is determined taking into account:
- constant pressure from roofs, ceilings, walls, etc.;
- temporary loads - snow, furniture, people.
The constant load is calculated depending on the materials used to assemble the building structures and their parameters. According to the standards, the mass of walls is supposed to be taken minus openings.
Weight of the slab itself when calculating solid foundations:
- on sandy soils is not taken into account;
- on clay is divided in half;
- on quicksand is taken into account in full.
Snow load on the foundation is determined according to table 10.1 of the joint venture. In this case, the parameter is taken for this particular area. Uniformly distributed loads for residential buildings are assumed to be 150 kg/m2. The weight of very heavy items that are supposed to be placed in the house is taken into account separately.
Selection of materials
The collection of loads on such foundations is calculated, thus, in the same way as on columnar and strip foundations. A solid foundation, like any other, is poured in most cases, of course, from a concrete mixture. By determining the thickness of such a foundation, you can easily calculate the amount of material needed for its construction.
Concrete for the construction of solid foundations is usually used grades B15-B25. You can, of course, pour slab foundations with the use of a better and more durable solution. However, this is usually considered impractical due to the increase in the cost of work. One of the absolute advantages of slab bases in any case is increased strength.
In addition to concrete, for the construction of suchthe foundation will also need materials such as sand, reinforcing bars and a waterproofing agent. To assemble the formwork, you will need to prepare the boards. According to the standards, it is necessary to use sawn timber with a thickness of at least 30 mm to create a casting mold for the slab base of the house. Before pouring the solution, the formwork boards are recommended to be laid with plastic wrap.
Concrete and rebar
Calculate the amount of material needed to pour such a base, in addition to the thickness of the slab, taking into account the fact that:
- at the edges, the foundation should extend beyond the building by at least 10 cm;
- reinforcement bars for the slab should be 6 cm shorter than it;
- rods are installed when pouring in increments of 40 cm;
- the sand cushion should also extend beyond the building by 10 cm;
- waterproofer when pouring fit with a small margin.
It is advisable to use roofing material as a waterproofing agent for pouring such a foundation.
Procedure of work
Slab foundations are poured in a few steps. Previously, a pit of design depth is excavated on the site.
Further, crushed stone is poured into the bottom of the pit to equip the drainage layer. Sand is laid on top to create a reinforcing pillow. This layer must be at least 15 cm thick.
On the sand cushion at the next stage, when arranging a solid slab foundation, a multi-tiered reinforcing cage is installed,associated with the use of wire. In order for the volumetric mesh to subsequently be in the thickness of concrete, special plastic stands or bars 5 cm thick are preliminarily placed at the bottom of the pit.
Further along the edges of the pit, formwork from boards is mounted. For its assembly, self-tapping screws and supports from a bar are used.
At the final stage, concrete is poured into the pit from the tank. In the process of laying the mixture, defects that appear are manually eliminated. From time to time, a layer of concrete in the pit is pierced with shovels to eliminate air bubbles. At the final stage, the surface of the plate is carefully leveled.
To fill the lattice solid foundation in the pit, before filling the crushed stone, they dig longitudinal trenches. The concrete poured into them subsequently forms ribs.
Final stage
After the foundation is poured, it is advisable to cover the slab with plastic wrap. In the future, within 2 weeks, the plate should be periodically moistened with water. This will avoid the appearance of surface cracks. It is allowed to erect walls on such a basis, as on any other, only after the concrete has fully matured. That is, approximately 28 days after pouring.
