The service life of any building directly depends on how reliable the foundation will be erected under it. Houses can be built on columnar, slab, pile, strip foundations. The most popular is the last type of bases. Strip foundations can be considered the best option in terms of price-reliability ratio. Such structures are able to serve the entire life of the building without the need for repair. 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
As you can already judge by their name, the foundations of this type are a continuous support tape under the walls of the building. Structures of this variety are poured in previously dug trenches. At the same time, their underground part is called the foundation itself, and the part that protrudes above the ground is called the base.
What are the varieties
The bases of this type are classified mainly according to two criteria:
- kind of used forerection material;
- degrees of depth.
Strip foundations can be erected from brick or concrete. Also, precast concrete structures of this type are often used as a support for buildings.
Brick for the construction of strip foundations is used exclusively ceramic full-bodied good quality. Concrete structures of this type are the most popular variety and are most often poured under buildings and structures. Metal reinforcement is used to increase the tensile strength of such tapes.
Precast concrete house foundations are assembled from long, strong blocks. The latter are laid in a trench in a tape with a connection with reinforcement and pouring joints with concrete.
The dimensions of strip foundations are determined, of course, including their height. Both ordinary structures of this type and shallow ones can be erected under buildings. In private housing construction, for example, the second type of bases 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 built only on very reliable solid soils. Ordinary 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 erected under buildings of absolutely any type:
- chopped;
- wireframe;
- brick;
- concrete;
- metal etc.
It is allowed to pour such structures, however, only on sufficiently strong soils. Do not build foundations of this type, for example, on quicksand, slopes, marshy soils, areas prone to movement. In such cases, buildings are built on more expensive slab or pile foundations.
Usually strip foundations are not poured under very light buildings - small wooden houses or baths, gazebos, verandas. In this case, columnar bases are most often erected. Such designs are reliable and at the same time cheaper than tape ones.
Features
The advantages of strip foundations primarily include their not too high cost. The price of such a structure, subject to proper design, will be low, no matter what size it may be. The strip foundation for the house should also be chosen because in this case it will be possible to equip the basement or cellar in the future. The advantages of such grounds are also:
- reliability and durability;
- maximally even distribution of the load from the walls of the house;
- versatility;
- ease of erection.
There are practically no cons of the foundations of this variety. The disadvantages of structures of this type can only be attributed to the fact that they cannot be erected on weak soils.
Features of the choice of materials
The strip foundation built under the building, of course, must first of all 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 be used for the construction of strip foundations.
Cement for pouring concrete tapes are getting high grades. At the same time, coarse sifted river sand is used. To reinforce concrete foundations of this type, a metal bar of 8-12 mm is purchased.
In addition to sand and cement, crushed stone is added to the mortar for strip bases. For such foundations, it is necessary to choose only moisture-resistant durable material of this type. Limestone, for example, is completely unsuitable for this purpose.
The dimensions 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. In this case, the calculation of indicators is carried out taking into account:
- building weight;
- Soil bearing capacity.
Building weight is determined by addition:
- weight of materials used for construction;
- of the foundation itself;
- snow in winter;
- all items that will bestay in the house (average 180 kg/m2).
Further, the total mass of the house found in this way is divided by the estimated area of \u200b\u200bthe foundation (the length is multiplied by the width). Thus, a specific load per 1 cm is obtained2. Further, 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 reconsider the width of the foundation upwards.
The dimensions of the strip foundation relative to the thickness of the wall may be different. For example, quite often low-rise buildings are erected, in which the bricks of the facades protrude beyond the base tape by several centimeters. Sometimes the foundation, on the contrary, can be wider than the walls. Thus, it is poured when, in the future, for example, facades are supposed to be faced with decorative bricks. But still, most often in the construction of houses in our time, the vertical planes of the basement and walls coincide.
Sizes of strip foundation blocks
Prefabricated bases of this type are built from standard blocks. Such structures are delivered to the site using special equipment. You can buy them at enterprises engaged in the manufacture of reinforced concrete products.
The marking of such blocks always contains the letters FL. The dimensions of this type of strip foundation are determined by the numbers after them. Beams FL6-24, for example, have dimensions of 240 x 60 x 30 cm, FL8-12 - 118 x 80 x30 cm etc.
Thus, it determines the dimensions of the GOST prefabricated strip foundation blocks. 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 prefabricated strip foundations and slabs. 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.
Filling technology in brief
After calculating the dimensions of the strip foundation, you can proceed to its actual construction. Most often, under buildings and structures, as already mentioned, monolithic foundations of this type are built. Their advantage, in comparison with brick ones, is the speed of construction, and in comparison with prefabricated ones, they are cheap. Tape monolithic foundations are poured using this technology:
- marking the site using the Egyptian triangle method;
- a trench is being dug to the design depth;
- a sand cushion is laid at the bottom of the trench with tamping water;
- pillow lining with roofing felt;
- formwork of wooden panels is installed in the trench;
- with the help of a knitting wire, a frame is assembled from a rod;
- special small stands 5 cm high are installed at the bottom of the pit;
- on coastersa metal frame is installed;
- concrete mix being poured.
The dimensions of the reinforcement for the strip foundation should be such that 5 cm remain from it to the formwork walls and the level of the top of the future basement. In this case, the frame, after pouring, will be completely immersed in the solution and will not begin to rust.
Cement mortar for the foundation is prepared in a concrete mixer. This allows you to make it as high quality and uniform as possible. Mixing is carried out in the proportion of cement/sand/crushed stone 1/3/4. In a concrete mixer, the dry components of the solution are first scrolled. Then water is added to them.
Features of construction
When building a strip foundation, you must, among other things, observe the following rules:
- the bottom of the trench before backfilling the sand cushion must be tamped and leveled;
- nails when assembling the formwork are supposed to be driven in from the outside;
- formwork walls to facilitate its dismantling after pouring can be laid with plastic wrap;
- the top of the base is leveled along the line stretched along the level;
- at the stage of foundation construction, holes are provided for engineering communications and ventilation;
- when pouring, the concrete mixture should be pierced from time to time with rods or a shovel to remove air.
The walls of the finished foundation are desirable, among other things,waterproof with bituminous mastic. It is also possible to simply add penetron to it at the stage of preparing the concrete solution for the tape. The top of the plinth of such a base is necessarily laid with two layers of roofing material. It is allowed to erect walls on a strip foundation only after the concrete has fully matured, that is, 28-30 days after pouring.
