Stabilized earth floors
• Earth floors are common in all developing countries, especially rural housing: the top soil (with organic matter) is removed and filled up with inorganic soil (clay, sand, gravel) well compacted. Surface coats of a clay - cow dung mix provide some stabilization, but have to be renewed frequently, to be effective.
• At Kassel College of Technology, Federal Republic of Germany, a rammed earth floor was developed, using a finely grained soil mix, stabilized with linseed oil: the clay content of the soil should be less than 15 %; no coarse sand or gravel; for 100 litres of dry soil, 3-4 litres of linseed oil (depending on clay content) are diluted with 1-2 litres of water.
• Several layers are required (see description overleaf) and the surface can be plain rammed earth in a grid of wooden lathing or small timber blocks embedded in the soil mix. Alternatively, compressed, stabilized soil blocks (made in a soil block press) can be used instead of the timber blocks.
Further information: Bibl.21.10.
• On a well-compacted, planed surface, coarse gravel (15 cm) is laid to prevent moisture absorption by capillary action.
• This is covered by a 3 - 5 cm layer of fine gravel or coarse sand and sealed with a waterproof membrane.
• In cold regions, a 10 cm layer of insulating material (eg expanded clay nodules) can be placed before
• the first layer of stabilized soil is evenly spread out and tamped with a manual rammer or vibrating plate.
• A grid (1.80 x 1.80 m) of sawn timber (10 x 10 cm) is laid on the first layer and filled with the soil mix and tamped.
• A grid (30 x 30 cm) of wooden laths (2 x 4 cm) is placed on the second layer and the final layer is filled in and carefully tamped. The top surface is then smoothed with the edge of a trowel under considerable pressure, to get "shiny" appearance.
• After several months of hardening, the surface can be treated with a thin coat of hard wax polish, for greater durability and moisture resistance (however, the strong smell may be a problem).
• Instead of the last two layers of soil mix, wooden blocks can be laid and the joints carefully filled with the same mix.
• Alternatively, stabilized soil blocks, made with a block press (see ANNEX) can be used instead of timber blocks. However, the blocks must be well stabilized (eg with lime or cement) to resist abrasion and moisture penetration.
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