Foundation

For constructing dwelling houses or summer cottages, panel, strip or pile foundations are mostly used. Upon selecting the type of the foundation, results of visual inspection or geodetic research are considered and after the bearing capacity of soil is calculated, the designing of a suitable foundation can start.
In Estonia, clay, sand, moraine and limestone are the most common soils. For all soil types, different layers and their thickness has to be separately established. The sand soil is most common for coastal areas and is considered to be the best soil regarding construction works; its moisture and water drainage features are extremely good. Sand soil can be easily transported during work and it can also be reused for later filling which in turn is remarkably cost-effective.
The most common soil in Estonia is, however, limestone and moraine. Limestone is also a good solid base for constructing a foundation. Nevertheless, problems can arise in directing excessive moisture away in case of high water level since the limestone massif tends to be completely level.
Moraine can also be considered to be a mixed soil. Moraine usually includes clay as well as sand. Here the sand-clay ratio starts to play a major role. In case of large clay content the soil is not the best option to build a foundation on. Clay itself is one of the most unstable soil types in addition to quicksand. Clay soil is common mostly near rivers and in soft wooded meadows where several dwelling areas have been founded during the fast period of Estonian development.
For construction works, Finnlamelli uses mostly strip foundations. This is mostly for the reasons of smaller expenses and shorter construction periods. In case of strip foundations, reinforced concrete footing is established under the bearing walls after earthwork and thickening of soil. On top of the footing, 3 or more rows of fibo-blocks are laid depending on the height of the established plinth and depth of the pit. Thermal insulation of 100 mm thick expanded polystyrene is mounted to the inner part of the foundation and filled with sand. After thickening of the sand, communications and under-floor heating of 150 mm is installed. A 100 mm thick reinforced concrete board is cast after instalment of fittings and heating pipes or heating cables.
The advantages of cast-in-place panel foundation are its large bearing capacity and that’s why this type of foundation is used mostly in case of unstable clay or quicksand soils. In case of panel foundations, the upper humus layer of the soil is peeled off, sand basis is made and height from the ground level is given according to the height markings. The thickened sand is then surrounded with expanded polystyrene, covered with durable hydro-isolation film and communications are installed. The whole prepared construction is cast in concrete after the construction of forms and fixation of fittings.
Construction of pile foundation is a possibility also in case of unstable soils. The deciding factor between panel and pile foundation is the cost of the construction works. In situations where the concrete terminal is too far or access to the site difficult, the pile foundation would be a more appropriate choice. If that is not the case, panel foundation would probably be more reasonable.