Strawbale house floors are usually one of four types: 1) wood; 2) adobe; 3) dry-set pavers; and 4) concrete.
Wood floors are used when the foundation system creates a basement or crawlspace. Floor joists (usually 2 by 12 lumber) rest on the foundation walls and span the distance between the walls. the method is like constructing a lid on top of the foundation walls. Plywood (usually tongue and groove) or OSB is used to cover the joists. Prudent floor builders take pains that the method used to attach plywood to joists results in a tight connection to prevent future floor squeaks. Methods that create squeak-free flors include using screws instead of nails, using construction adhesives in addition to screws or nails, and diagonal nailing or using ringshank or screw-type nails when nailing.
Adobe floors are a traditional flooring method. Adobe is a mixture of straw and mud which is poured into place, then trowelled smooth and allowed to dry. The straw acts to bind the mixture together and prevent cracks. The "mud" part of the mix must have a significant percentage of clay. Once the floor dries, it can be oiled with linseed oil, and can even be colored with dyes. Adobe floors are often referred top as being very comfortable.
Brick pavers are often "dry-set" in a bed of sand to avoid using concrete, and also when the radiant floor heat is to be used. The floor area is filled with sand up to the desired level and then sand is then packed using a soil vibrator. Brick pavers are arranged in whateever pattern is sought, and fine sand is sprinkled over the pavers and swept into the cracks between the pavers to hlod them in position.
Concrete floors are sometimes chosen in the interests of simplicity and speed, and also when radiant floor heat is employed. As noted before, the "hardness" of concrete is often described as unfriendly. One little used method to improve the feel of concrete floors is to glue or nail (concrete nails) pressure treated 2 by X lumber on the concrete flat-ways (not on-edge) and then nail down plywood, OSB, or flooring. This method can improve the feel of the floor, but it represents added cost and material redundency.
All floor require moisture barriers under them to prevent moisture from moving into the house from the earth beneath. This is accomplished using 6 mil layer (s) of polyethylene, and adequate sealing of the poly to the foundation walls with tar. Care must be taken to ensure the integrity of polyethylene is maintained.
All floors in temperate and cold climates should have insulation installed beneath the floor. This can take the form of fiberglass batts for floors using joists, or rigid foam insulation in the case of poured concrete or adobe floors. Adequate insulation will help ensure a comfortable house. Inadequate insulation can almost never be improved, so the builder needs to make the right decision before the floor is installed.
