Foundation is the key part of any building, so the lifetime of a house to be built largely depends on the technology you use to build its foundation. The price of a reliable and durable foundation makes up at least 20% of the cost of the whole house. Therefore, before you start building anything, you want to carry out a proper geotechnical survey to determine the soil type and calculate the load of your future house, taking into account a possible settlement of the foundation.
Soils may be deformed under loads and with temperature changes. Clayey and loamy soils swell during frost penetration. Only rock soils do not settle down, but these are quite rarely used for construction. Choosing the foundation design depends on many factors.
The criteria that influence the choice of the foundation design and depth are as follows:
The foundation transfers the load of the whole house to the earth and resists the loads from the earth. All these loads are calculated thoroughly prior to starting any construction work.
Upward Forces of Swelling Soils
Swelling soils (clays and loams) take in a lot of water which expands (swells) in winter. This results in great stresses in soils which lift buildings and structures leading to deformations, cracks, etc. See how soil types affect the foundation design choice.
Lateral Loads on Foundations
Lateral loads are caused by swelling soils, snow, winds, etc. The lateral loads push foundation walls in, especially when the foundation is empty, that is, when there is a cellar.
The groundwater level is determined by drilling at least 4 wells at the construction site. Samples of soil and water are taken from there to conduct laboratory analyses. For a wooden house, well depths of up to 5 m are sufficient, for brick or stone houses they should be at least 7 m to 10 m.
Soil Frost Line
It is very important to determine the depth of the soil frost line. A foundation built below the frost line cannot guarantee any protection against the effects of frost heave. This factor can be minimized by reducing the lateral surface of the foundation by forming something like a trapezoid or filling the free space inside the foundation with non-swelling soil.
The Purpose and Design of the House
If you decide to build a brick house, you have to determine the thickness of the walls, the height of the house, the need for a basement (cellar), a utility area, a garage. If it is a strip foundation, you’ll have to calculate the depth which will be best for the given soil type. It’s strip foundations that walls of reinforced concrete panels and blocks are erected on. You can build a slab foundation if you are building your house on a hill slope, in clay or sandy soil, swampy soil, etc. If it is a wood-frame house, a low-depth foundation will be enough.