Depth of foundation of the basement

Depth of foundation of the basement

Private construction allows the use of various supporting structures. One of the most durable types of bases is the ribbon foundation. He successfully withstands loads of cottages made of timber, various blocks and bricks. He is not afraid of seasonal soil displacements and the complex nature of soil behavior. The correct depth of the strip foundation is one of the most important indicators ensuring the reliability of the structure.

Methods for laying the foundation foundation

Having stopped on the variant of erection of the tape base, it is important to determine the suitable construction, which are:

  • unshaded (NWFP);
  • shallow (MZLF);
  • deep buried (GLC).

The choice is made based on a combination of factors that are individual in each case. This includes:

  • Soil properties. The height of the ribbon foundation is largely determined by the characteristics of the soil: its propensity for whipping, the depth of freezing and other properties.
  • The level of groundwater (GWP) has a significant effect on the depth of the LF deposit.
  • Massiveness of future construction. In this paragraph, take into account the material used in the construction of walls and roofing, the type of overlap and finish.
  • In addition to the main load on the strip foundation, additional pressure is taken into account. Usually it is the weight of the snow cover, the weight of the furniture and so on.


The undampled ribbon foundation was not widely used in construction due to its low strength characteristics. The reason for the construction, which is completely located above the ground, deepens exclusively the pillow consisting of sand or its mixture with gravel.

Finely recessed

The shallowly buried foundation copes with its functions much more efficiently. But the scope of its application is limited to the type of soil in the building site. Optimal for soil not prone to whipping. It is usually used in the construction of buildings that do not have a significant mass: this includes wooden, foam concrete or compact brick buildings.

Important! A belt foundation with a shallow depth of deposit is erected on the site, provided there is no groundwater near the surface.

The combination of all three factors gives the full right to refer to the design of the MLF for the home. At the same time, there is no need to take into account the depth of freezing.

Deeply deepened

Belt foundation of deep laying is considered the most reliable of all options, when the base is applied tape. Basic conditions of arrangement:

  • It is necessary to deepen 0.1-0.2 m below the freezing point;
  • under the sole should be a solid ground.

The presence of peatlands or marshy soil obliges to shift the depth of the embankment to a line below these layers. Such a construction is extremely expensive in terms of financial, labor and temporary investments. It is more practical to make a combined version, when the strip foundation is supplemented by supporting poles leaving below the moving soil layer.

One more situation, when they turn to the variant of the ribbon foundation, the depth of which is quite large - the necessity of equipping the basement. In this case, the supporting structure serves as a wall for the basement room.

Collection of data on the geological situation

To determine what depth to do the strip foundation will help data from geological prospecting. Any typical project needs to refine the data from a particular site. The brigade, equipped with special equipment and trained workers, will carry out all the research. To get a full picture of the characteristics of the ground, it is required to make a minimum of three wells, they drill to a depth exceeding 8 meters. The samples are sent to the laboratory for further research. As a result, a document is issued in which the following information is reflected:

  • type of soil;
  • density;
  • load bearing capacity.

Data is used to design a strip foundation or to make changes to a sample document.

Dependence of the depth of the LF location on the freezing level is presented in the following table:

On what depth to dig a trench under the tape foundation in many respects defines and UGV. The process can develop in two ways: when the GWB is below the freezing point or when it is higher.

The first position is much more profitable for arranging the ribbon foundation. In this case, groundwater does not significantly affect the depth of the support structure.

Comment! When the ribbon foundation of a shallow depth is erected on clay or loam, the depth of the foundation must be lowered to at least half the freezing level. On soils not prone to whipping, this condition is not necessary.

That is, in a region with a freezing line of 1.3 m, the shallowly recessed ribbon base is located at a level of 0.65 m under the ground.

The answer to the question of how deep the foundation, if the GWT is high, depends on the type of soil. The index of the location does not depend on the UGW, provided that the basement is erected on the following types of soil:

  • gravel;
  • sandy coarse-grained;
  • rocky ground.

The remaining types of soil with high GW require that a strip foundation be installed below the freezing point by 0.1-0.2 m, that is, to turn to the technology of erecting a deeply buried structure.

How to reduce the depth of the LF

The results of calculations can give a disappointing result when it is required to equip the buried bottom foundation, which entails significant investments of forces and means. There arises a logical question, how to reduce costs by reducing the depth of the deposit. There are three main approaches to solving the problem:

  • By changing the freezing line. Of course, no one is able to correct the climatic conditions of the region. But it is quite real to insulate the very structure of the strip foundation and the soil located on the outside.
  • A quality drainage system provides groundwater abstraction, significantly reducing their harmful effects on the underground part of the supporting structure. Thus, the need to erect a recessed ribbon foundation will disappear, transferring it to the status of the MZLF.
  • Arrangement of pillows. A fairly low occurrence of soil prone to whipping requires the placement of a concrete foundation to a depth exceeding a dangerous level. Cushion of sand or a combined composition with gravel will help to eliminate the risk of pushing or deforming the supporting structure. Initially, a trench is being prepared, the bottom of which is located on solid rock. Then a rigid cushion is formed, and its dimensions exceed the base of the basement.
Advice! The most effective is the combined approach, when the pillow is supplemented by a drainage system and a high-quality thermal insulation of the band support structure.

Optimal depth of the foundation, taking into account the attendant factors

The depth of the concrete foundation is not always dependent on the characteristics of the soil and the expected load of the future structure. The desire to have a basement will require the installation of a buried basement foundation, and the location of its sole should be at least 0.4 m below the floor. At the same time, it should not reach the groundwater level, but overcome the freezing line of the ground.

The design of the belt foundation necessarily includes the presence of a drain cushion under the base. The basis is provided by materials that are not prone to whipping (sandy-gravel composition or exceptionally coarse sand), which are carefully compacted after filling. Accelerated drainage of water and uniform distribution of pressure on the ground - the main functions of padding.

The depth of the concrete foundation is fluctuating from the freezing index of the ground and varies by region. Deep-deep ribbon foundation is subject to the influence of lateral punching forces. To prevent the destruction or deformation of the supporting structure will help the use of high-grade reinforced concrete reinforced with a reinforced frame, in conjunction with backfilling of the side surfaces with non-stiff material.

If you plan to erect a house without a basement on a site with a stable ground, it is enough to install the MZFL. Its average depth of embedment is from 0.5 to 0.7 m. Depending on the calculated load of the structure, the width of the tape base and other design parameters are determined.

Features of the MZLF

The task of building a foundation with our own hands is quite feasible. To provide MZFL strength and durability will help meet a number of conditions:

  • The tape foundation is poured in one approach, the reinforced concrete M200-M300 is used for the mortar.
  • The width of the trench exceeds the size of the supporting structure for further insulation and padding.
  • Accelerated water removal and uniform distribution of the load is facilitated by a drainage cushion under the sole of the belt foundation.
  • Thermal insulation of the EPP soles helps to reduce the effect of shearing forces during the frost period.
  • Waterproofing and warming the side surfaces of the belt foundation significantly increases its service life.

Correct calculation of the depth of the installation and compliance with the conditions of the construction in the process of erection will ensure the tape foundation and the entire structure of integrity for a long period.

  • Tape foundation for a two-storey brick house

  • How to put the foundation under the foundation

  • Ribbon foundation for house 6x6

  • Tape foundation for a house with a basement

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