The life of any building directly depends on how reliable the foundation will be built under it. Houses can be built on the foundations of columnar, slab, pile, tape. In this case, the last type of bases is the most popular. Strip foundations can be considered the best option in terms of price and reliability. Such structures can serve the entire life of the building without the need for repairs. The dimensions of the strip foundation depend on the weight of the house and the bearing capacity of the soil on the site.
What is a
As can already be judged by their name, the foundations of this type are a solid support tape under the walls of the building. The structures of this variety are poured in previously dug trenches. Moreover, their part located underground is called the foundation itself, and the protruding above the ground - the base.
What varieties exist
The bases of this type are classified mainly on two grounds:
Strip foundations can be built of brick or concrete. Also, prefabricated reinforced concrete structures of this type are often used as a support for buildings.
Brick for the construction of strip foundations is used exclusively ceramic solid of good quality. Concrete structures of this type are the most popular variety and are poured under buildings and structures most often. To reinforce the tensile strength of such tapes, metal reinforcement is used.
Prefabricated reinforced concrete foundations of houses are assembled from long strong blocks. The latter are placed in a trench in a tape with a connection with reinforcement and pouring joints with concrete.
The dimensions of the strip foundations are determined, of course, including their height. Both conventional structures of this type and shallow ones can be built under buildings. In private housing construction, for example, the second type of foundations is the most popular.
Such foundations are usually buried in the ground by no more than 30-40 cm. Of course, such foundations are allowed to be erected only on very reliable strong soils. Conventional strip foundations are poured to a depth below the freezing of the soil - that is, 0.7-1.5 m, depending on the region.
Features of use
Strip foundations can be built under buildings of absolutely any type:
chopped;
wireframe;
brick;
concrete;
metal, etc.
It is permitted to flood such structures, however, only on sufficiently strong soils. Foundations of this type are not being built, for example, on quicksand, slopes, marshy soils, areas prone to shifts. In such cases, buildings are built on more expensive slab or pile foundations.
Usually strip foundations are also not poured under very light constructions - small wooden houses or baths, arbors, verandas. In this case, most often erected columnar base. Such designs are reliable and at the same time cheaper than tape.
Specifications
The advantages of strip foundations in the first place include their not too high cost. The price of such a design, subject to proper design, will be low, whatever its size. The strip foundation for the house should also be chosen because in this case in the future it will be possible to equip the basement or cellar. The advantages of such bases are also:
reliability and durability;
the most uniform load distribution from the walls of the house;
universality;
simplicity of construction.
There are practically no disadvantages in the foundations of this variety. The only drawbacks of structures of this type are that they cannot be erected on soft soils.
Features of the choice of materials
The strip foundation built under the building, of course, in the first place should be as reliable as possible. Therefore, materials for such structures always try to choose the highest quality. Silicate brick, for example, since it does not differ in moisture resistance, is not allowed to use for the construction of strip foundations.
Cement for pouring concrete strips acquire high grades. At the same time, sand is used for large river screened. To reinforce concrete foundations of this type, a metal rod of 8-12 mm is purchased.
In addition to sand and cement, crushed stone is added to the solution for strip substrates. To choose for such foundations relies only moisture-resistant durable material of this type. Crushed lime, for example, is completely unsuitable for this purpose.
Sizes of the strip foundation: calculations and design
The foundations of this type are poured in such a way that all external and internal walls of the house subsequently rest on the tapes. When designing, in addition to the depth of laying, they are determined with the width of the foundation, as well as the height of the base. The calculation of indicators in this case is carried out taking into account:
The weight of the building is determined by adding:
Further, the total mass of the house found in this way is divided by the estimated area of the foundation (the length is multiplied by the width). Thus, a specific load of 1 cm 2 is obtained. Then, according to a special table, they will find out whether the soil under the foundation can withstand such pressure.
If the bearing capacity of the soil is less than the load from the house, the necessary adjustments are made to the project. That is, they are reviewing the width of the foundation in a larger direction.
The dimensions of the strip foundation with respect to the thickness of the wall can be different. For example, quite often low-rise houses are erected, in which the bricks of the facades extend beyond the base tape by several centimeters. Sometimes the foundation, on the contrary, can be wider than the walls. Thus, it is poured when later, for example, the facades are supposed to be lined with decorative bricks. But still, most often during the construction of houses in our time, the vertical planes of the base and walls coincide.
Sizes of blocks of the strip foundation
Prefabricated bases of this type are built from standard blocks. Such structures are delivered to the site using special equipment. You can purchase them at enterprises engaged in the manufacture of reinforced concrete products.
The labeling of such blocks always contains the letters PL. The dimensions of the strip foundation of this type are determined by the numbers following them. Beams FL6-24, for example, have dimensions of 240 x 60 x 30 cm, FL8-12 - 118 x 80 x 30 cm, etc.
Thus, it determines the dimensions of the blocks of the prefabricated strip foundation GOST. Calculations in this case are made according to the same principle as for monolithic bases of this type.
In some cases, they can be used in the construction of a prefabricated strip foundation and slab. The dimensions of such reinforced concrete structures are also standard. Their width can vary between 600-3200 mm. Reinforced concrete structures of this type are used to distribute the load from the walls.
Brief fill technology
After calculating the dimensions of the strip foundation, you can begin to actually erect it. Most often, under the buildings and structures, as already mentioned, monolithic foundations of this type are built. Their advantage, in comparison with brick, is the speed of construction, and in comparison with prefabricated - cheapness. Tape monolithic foundations are poured according to this technology:
marking the site according to the method of the Egyptian triangle;
digging a trench of design depth;
a sand cushion is laid at the bottom of the trench with tamping water;
the pillow is laid out with ruberoid;
formwork made of wooden panels is installed in the trench;
with the help of a knitting wire, the frame of the rod is assembled;
special small supports 5 cm high are installed at the bottom of the pit;
a metal frame is installed on the supports;
concrete mixture is poured.
The dimensions of the reinforcement for the strip foundation should be such that from it to the formwork walls and the level of the top of the future base, there should be 5 cm each. In this case, the frame after pouring will be completely immersed in the solution and subsequently will not begin to rust.
The cement mortar for the foundation is prepared in a concrete mixer. This allows you to make it as high quality and uniform. Kneading is performed in the proportion of cement / sand / crushed stone 1/3/4. In a concrete mixer, the dry components of the mortar first scroll. Then water is added to them.
Features of the construction
When constructing a strip foundation, you must, among other things, observe the following rules:
the bottom of the trench must be tamped and leveled before filling the sand cushion;
when assembling the formwork it is supposed to drive the nails from the outside;
the walls of the formwork to facilitate its dismantling after pouring can be laid with plastic wrap;
the top of the plinth is leveled according to the line tensioned at the level;
at the stage of construction of the foundation, holes are provided for summing up utilities and ventilation;
when pouring the concrete mixture, from time to time it should be pierced with rods or a shovel to remove air.
It is desirable to waterproof the walls of the finished foundation, among other things, with waterproofing with bituminous mastic. You can also at the stage of preparing a concrete mortar for the tape just add a penetron to it. The top of the basement of such a base is without fail laid by two layers of roofing material. To erect walls on a strip foundation is allowed only after the concrete has fully matured, that is, after 28-30 days after pouring.