If on the territory where the construction of the house is planned, there was sandy soil, then we can assume that you are lucky. Such soil is better than peat or clay. Its bearing capacity is great, which is especially true for coarse sand. It passes water well, therefore it is not subject to frost heaving, and the finest sand acts as an exception. But even in this case, the design must be supplemented by a drainage system, the features of the device of which are discussed below.
Varieties of sandy soils
If you believe that when building a house on sandy soil there should not be any problems at all, then you should know that this is not entirely true. In order to avoid mistakes, at the first stage of the work it is necessary to carry out geodetic studies that will allow to determine the type of soil. He can be:
- dusty;
- medium grained;
- fine-grained;
- gravelly.
Dusty soil has a large number of grains of sand with dimensions that do not exceed 0.1 mm. This sand looks like dust, and the specific gravity of fine-grained grains of sand is 75%. Such soil is considered quite complex, because it is prone to saturate with groundwater and the formation of quicksand. But even in this case there is a panacea.
Fine dust sand consists almost entirely of sand particles (more than 75%). But their size reaches already 0.25 mm. With abundant moisture, such soil loses its bearing capacity, therefore, structures require additional waterproofing.
What foundation to choose for sandy soil?
Before building a foundation on the sand for the home, you must choose its kind. For example, any base is suitable for large sandy soils. However, tape or column structures are most often used, which can be based on foundation blocks or ceramic bricks, which, however, reduce the bearing capacity of the structure.
When the house is planned to be built without a basement, it is better to erect a shallow, shallow foundation foundation. You can also choose a columnar base, it is suitable for the house from light materials, such as panels or wood. When choosing a foundation on sandy soil, you must determine how small grains of sand are at the base of the soil. If the sand is quite fine, dusty, then the best option would be a monolithic tape shallow foundation.
To reduce the effect of frost heaving, it is better to make the base trapezoidal, expanding downward. Among the advantages of the strip foundation is not such a strong effect on soil erosion. Before starting to fill the trench, it is necessary to waterproof it, laying the bottom with a special film.
If construction on sand involves the construction of a heavy building, it is better to equip a pile or pile-tape version. When the soil is weak, it is better to make a foundation on a sand cushion of coarse sand. For weak soil, a pile-tape foundation is suitable. It lays well on soil prone to the formation of quicksand.
For the device of such structures, marking is made and a foundation pit is dug. Formwork is installed in it, and then wells are drilled at the intersections of the tape. Their depth should be such as to be able to achieve reliable soil.
When choosing the type of foundation on quicksand, it is better to give preference to a pile-tape structure, which will have asbestos-cement pipes fixed by struts at the base of the supports. Inside, a third of the depth is poured into the solution, and after the pipe rises, so that a thickening forms from below.
On fine sandy soil you can build a pile foundation. It is stable and durable, because the piles will be located below the freezing line. Such a design is more reliable than a columnar one, which, under the influence of heaving, can skew or disperse.
The pile-screw foundation is also installed on the quicksand, since the supports will reach solid soil. The slab foundation in the sand is also called floating. This is due to its movement along with the soil. Therefore, the design is almost not subject to destruction. It is reliable and durable, but is expensive due to the consumption of material. A slab base is suitable for moving soil, for example on a hillside. Under such conditions, the house will sail with the stove without being damaged.
Features of the strip foundation
The strip foundation in the sand does not go too deep, up to a maximum of 70 cm. A frame, wooden, panel or small brick house can be put on such a structure. Excellent on the strip foundation will be held and the building of foam blocks.
The tape design can be prefabricated or monolithic. For massive houses with a basement or residential base, a deeply buried base is made. The depth of the foundation in the sand for a brick house is 20 cm below the level of soil freezing. When installing a buried foundation, it should be waterproofed from all sides, making a full drainage. This will allow you to build a house with a basement, even with high groundwater.
Strip foundation construction
The strip foundation in the sand is built according to a certain algorithm. At the first stage, it is necessary to remove the fertile soil layer from the site, level the surface and mark it. To do this, use a plan or project.
Then an 80-cm trench is excavated, the width of which is 20 cm greater than the future walls. The next step will be the construction of the formwork:
- from plywood;
- professional sheet;
- edged boards.
Inside, the structure is covered with polyethylene. For a shallow tape, reinforcement plays an important role. At the final stage, the formwork is poured with concrete.
Drainage foundation
The foundation in the sand should be supplemented with drainage, which is especially important for buildings on fine-grained soil. The most effective closed systems, where the main role is played by pipes. For the manufacture of one of them, it is necessary to take a sewer plastic pipe in which holes are drilled. Products are wrapped with geotextiles and laid in a trench dug around the house. On the surface, it is necessary to make bends that are covered with gravel, and from above everything is covered with geotextiles and soil.
Construction of a pile and strip foundation
The foundation in the sand can be pile-tape. For its arrangement, markup is made on the territory and a foundation pit is excavated. Formwork is installed in it, and then wells are drilled at the intersections of the tape. Asbestos-cement pipes go down there . Inside the solution is poured.
Fittings are placed in the pipe, and then the solution is poured to the end. The reinforcement must protrude above the surface so that it can be connected with the reinforcement of the foundation tape. If the soil is not very moist, and water does not enter the well, then the piles can be poured without using pipes.
After preparing the wells, their lower part is expanded by a plow, and then reinforcement is placed there and concrete is poured. After the piles harden, you can begin to form the foundation tape. In order to get a stronger structure, it is necessary to fill at a time so that between the layers there are no seams that reduce strength. Welding parts of the reinforcement is not recommended, because corrosion will form in the joints. Before continuing work after pouring the base on fine sand, it should be left for 6 months.
Construction of a pile foundation
A pile foundation in the sand can be built if the soil is fine-grained. The design is solid, and the supports are located below the freezing level. Piles can be:
As soon as the wells are ready, it is possible to make pipes from roofing material. The upper part of the pipes is made of several layers, and then the material is pulled together by soft steel wire, which will become part of the formwork. After installing the pipe in the well, it is important to make sure that the pit is not filled with water for more than a quarter of the volume.
Roofing material during concrete pouring is necessary so that the cement milk does not go into the soil, and frosty heaving forces will affect the rough wall of the piles, and not on the smooth, obtained thanks to the roofing material. For a well with roofing material, a reinforcing cage should be made. For this, 6 mm rods are used. They are fastened together by crossbars.
Pile screw foundation
A screw pile is screwed into the soil by the efforts of several people. One of them constantly monitors the level of the support, while others try to screw it to the desired level. After the product is below the level of soil freezing, it is cut at one level and poured with concrete. Cement mortar must necessarily get inside the pile pipe, as this will strengthen the support and save the metal from corrosion.
After concrete hardens, a metal tip is welded to the screw piles. In order to ensure a uniform load of the weight of the building, it is necessary to tie the piles. For additional strength in the construction of heavy houses, the strapping is performed from a channel.
The upper part of the foundation is a grillage. It will distribute the load of the supporting elements. On an uneven area, the supports will have different lengths, but their upper part should be at the same level. It will take approximately 45 minutes to install one pile.
Hydro and thermal insulation of the base on sandy soil
Thermal and waterproofing allows you to protect the foundation from destruction by frost heaving and moisture. To create a waterproofing layer, you can use water-based mastic or bitumen. At the same time, mastics based on organic solvents should be abandoned, since their components can react to the insulation and destroy it.
Extruded polystyrene, which is also called penoplex, will be an excellent material for thermal insulation of the base. Its plates are conveniently connected to each other and fixed to the foundation with the help of special glue.
Additional recommendations for warming the foundation
Before starting work on the thermal insulation of the base, waterproofing should be done. For this, polymer mastic is usually used. For gluing the boards, glue should be prepared, applied to the canvas pointwise or on the entire surface.
After setting the glue, you can proceed to fasten the next plate, combining the mounting grooves. To improve the quality of thermal insulation, it is permissible to install a second layer, the elements of which will be staggered.
Finally
Depending on the type of sand, you will need to choose a type of foundation. If there is coarse gravel sand on the territory, then you have a lot of freedom in choosing the foundation. But when building on quicksand and fine sand, you can choose only certain types of foundations. The optimal solutions in this case will be pile-tape, tape or pile foundations. Particular attention should be paid to hydro and thermal insulation, which will protect the house from movement of soil and moisture.