If there is sandy soil on the territory where the construction of the house is planned, then we can assume that you are lucky. Such soil is better than peat or clay soil. 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 with a drainage system, the features of which are discussed below.
Varieties of sandy soils
If you think that when building a house on sandy soil, there should be no problems at all, 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 determine the type of soil. It can be:
- dusty;
- medium grain;
- fine-grained;
- gravel.
Dusty soil has a large number of grains of sand with sizes that do not exceed 0.1 mm. This sandlooks like dust, and the specific gravity of fine sand grains is 75%. Such soil is considered quite difficult, because it is prone to groundwater saturation and the formation of quicksand. But even in this case, there is a panacea.
Fine-grained dusty sand is almost entirely composed of sand particles (more than 75%). But their size already reaches 0.25 mm. With abundant moisture, such soil loses its bearing capacity, so the structures require additional waterproofing.
Which foundation to choose for sandy soil?
Before you build a foundation in the sand for your house, you must choose its type. For example, any base is suitable for large sandy soils. However, more commonly used strip or column structures, which may be based on foundation blocks or ceramic bricks, which, however, reduce the bearing capacity of the structure.
When a house is planned to be built without a basement, it is better to build a tape shallow foundation. You can also choose a column base, it is suitable for a house made of light materials, such as panels or wood. When choosing a foundation on sandy soil, you must determine how small the 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 strip shallow foundation.
To reduce the effect of frost heaving, it is better to make the base trapezoidal, expanding downwards. Among the advantages of a strip foundation is not such a strong effect on soil erosion. Before the beginningpouring the trench must be waterproofed by 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 option. When the soil is weak, it is better to make a foundation on a sand cushion of coarse sand. For weak soil, a pile-strip foundation is suitable. It fits well on soil prone to the formation of quicksand.
For the construction of such structures, markings are 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 that it is possible to reach reliable soil.
When choosing the type of foundation on quicksand, it is better to give preference to a pile-tape structure, which at the base of the supports will have asbestos-cement pipes fixed with spacers. A solution is poured inside a third of the depth, and then the pipe rises so that a thickening forms from below.
On shallow 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 warp or part.
The pile-screw foundation is also installed on quicksand, as the supports will reach solid ground. The slab foundation on the sand is also called floating. This is due to its movement along with the ground. Therefore, the structure is almost not subject to destruction. It is reliable and durable, but it is expensive due to the consumption of material. Suitable slab base formoving soil, such as on a hillside. Under such conditions, the house will float with the stove without being damaged.
Features of strip foundation
The strip foundation on the sand does not deepen too much, a maximum of 70 cm. It will be possible to put a frame, wooden, panel or small brick house on such a structure. The foam block building will also be held perfectly on the strip foundation.
Strip construction can be prefabricated or monolithic. For massive houses with a basement or a residential basement, a deeply buried base is made. The depth of the foundation on the sand for a brick house is 20 cm below the freezing level of the soil. When constructing a deep 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.
Construction of a strip foundation
The strip foundation on 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. For this, a plan or project is used.
Then an 80 cm trench is dug, the width of which is 20 cm wider than the future walls. The next step will be the construction of the formwork:
- from plywood;
- profiled sheet;
- cut boards.
Inside the construction is covered with polyethylene. For a shallow tape, reinforcement plays an important role. At the final stagethe formwork is poured with concrete.
Addition of the foundation with drainage
The foundation on the sand must be supplemented with drainage, which is especially important for buildings on fine soil. The most effective are closed systems, where pipes play the main role. For the manufacture of one of them, it is necessary to take a sewer plastic pipe in which holes are drilled. Products are wrapped in geotextiles and placed in a trench dug around the house. On the surface, it is necessary to make bends, which are covered with gravel, and from above everything is covered with geotextiles and soil.
Construction of a pile-strip foundation
The foundation on the sand can be pile-tape. For its device, markings are made on the territory and a foundation pit is dug. Formwork is installed in it, and then wells are drilled at the intersections of the tape. Asbestos-cement pipes are lowered there. The solution is poured inside.
The fitting is placed in the pipe, and then the solution is poured to the end. The rebar must protrude above the surface so that it can be connected to the reinforcement of the foundation tape. If the soil is not very wet, and no water enters 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 have solidified, you can begin to form the foundation tape. In order to obtain a stronger structure, it is necessary to carry outpouring at a time so that there are no seams between the layers that reduce strength. It is not recommended to weld parts of the reinforcement, because corrosion will form in the places of the seams. After pouring the base on fine sand, it should be left for 6 months before continuing with work.
Pile foundation construction
A pile foundation on sand can be built if the soil is fine-grained. The structure is solid, and the supports are located below the freezing level. Piles can be:
- stuffed;
- screw;
- bored.
As soon as the wells are ready, you can make pipes from roofing material. The upper part of the pipes is made of several layers, and then the material is pulled together with 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 more than a quarter of the volume.
Roofing material when pouring concrete is necessary so that the cement milk does not go into the soil, and frost heaving forces will act on the rough pile wall, and not on the smooth one 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 with 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 the others try to screw it in to the desired mark. After the productturned out to be below the freezing level of the soil, it is cut off at one level and poured with concrete. The cement mortar must get inside the pile pipe, as this will strengthen the support and save the metal from corrosion.
After the concrete has hardened, a metal head is welded to the screw piles. In order to ensure a uniform load from the weight of the building, it is necessary to tie the piles. For additional strength during 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 load-bearing elements. On an uneven section, 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
Heat and waterproofing helps 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 foam, also called polystyrene foam, 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 a special adhesive.
Additional recommendations for foundation insulation
Before starting work on the thermal insulation of the base, it is necessary to carry out coating waterproofing. For this, usuallypolymer paste is used. For gluing the boards, glue should be prepared, applied to the sheets pointwise or on the entire surface.
After the adhesive has set, you can proceed to fixing the next plate, aligning the mounting grooves. To improve the quality of thermal insulation, it is permissible to install a second layer, the elements of which will be arranged in a checkerboard pattern.
In closing
Depending on the type of sand, you will need to choose the type of foundation. If there is coarse gravel sand on the territory, then you have a lot of freedom in choosing the base. 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, strip or pile foundations. Particular attention should be paid to hydro and thermal insulation, which will protect the house from soil movements and moisture.
