The foundation of the house is a set of underground structures on which walls or poles rest and which transmits loads to the base of the structure. The supporting surface of the foundation is called a pad, the structure forming it a footing and the part extending on the surface a socle.
Strip foundations, base slabs or pile foundations are mostly used in building living houses or summer cottages.
As a log house is light, it does not require a foundation that is very complex or solid. As the foundation is directly related to the structure of the foundation joists of the house, it is important to know the type of the planned foundation at the beginning of the design work.
The choice of the foundation is based on the results gathered via visual inspection or geodetic surveys. After the load-bearing capacity of the soil has been calculated, designing a foundation suitable for the surface can begin.
The choice of the foundation of the log house should be based on the surface and size of the house. If the soil contains much clay, limestone or sand, it is recommended to use a strip foundation. If the ground is lower, the foundation should be built on piles.
Due to lower costs and shorter building process, log houses are often built on a strip foundation. To build a strip foundation, a reinforced concrete footing is built under the load-bearing walls after excavation work and soil compaction has been completed. Usually three or more rows of Fibo blocks are laid on the footing according to the designed socle height and excavation depth. The inner part of the foundation socle is insulated with foam polystyrene and filled with sand. After sand has been compacted, utility lines and insulation under the floor is installed. After the framework and heating pipes or cables of the floor have been installed, a reinforced concrete plate is poured on top of them.
An advantage of a monolithic slab foundation is its great load-bearing capacity, due to which this type of a foundation is used in instances of unstable soils consisting of clay or floating sand. For slab foundations the top humus layer of the soil is removed, a sand base is made and the height from the ground is given according to the fixed points. Thereafter, the compacted sand is surrounded with foam polystyrene, it is covered with a durable waterproofing film and utility lines are installed. After the formwork has been built and reinforcement has been bound, the entire prepared structure is poured in concrete.
The major difference between a strip foundation and slab foundation is that the floor of a slab foundation is cast together with the foundation part, but for a strip foundation the floor structure stands separately from the foundation.
A pile foundation can also be built on unstable surfaces. Piles or poles are sunk (or a hole is dug and poles are cast from concrete) so deep in the ground that a sufficient load-bearing capacity to build a house on them is ensured. One of the advantages of a pile foundation is its low cost.
The foundation joists of the house are installed on the foundation. Later the walls are installed on the foundation joists. Usually the beams of the foundation joists are impregnated with a wood preservative. Impregnated foundation joists are not installed directly on the concrete but on bituminous material (not included in the delivery). This prevents penetration of moisture in wood. In some cases, a wall beam is installed directly on the foundation without foundation joists. In such a case, it is recommended to impregnate the lower row of logs with a wood preservative.
POSSIBLE CROSS-SECTIONS OF FLOOR JOISTS:
- 45 x 70 mm
- 60 x 80 mm
- 45 x 95 mm
- 45 x 145 mm
- 45 x 195 mm
In special cases, glue-laminated timber may also be used.
Insulation of the foundation/floor – Depending on the height of the floor joists, insulation can be installed between the floor joists (under the floor boards), if the foundation has not already been insulated.
Log houses can be provided with any type of floor (floor tiles, boarding, etc.). Palmako delivers its houses with a wooden floor, in which case there are several installation options depending on the type of the foundation. In a standard delivery, Palmako houses are provided with floor joists with a height of 80 mm suitable to be used both with a slab or strip foundation. One can choose between two board thicknesses: 19 mm and 28 mm.