What Kind of Foundation Is Needed for a Ferrocement House?

Ferrocement Construction

• This type of construction uses Portland cement and sand over small-diameter steel rebar and wire or steel mesh. The wire allows a relatively thin coating of cement, with no need for forms, while the material dries. Once hardened, the steel wires embedded in the structure make it less brittle than conventional concrete or cement, reducing the risk of severe damage during earthquakes, hurricanes or other natural disasters.

T-Shaped Foundations

• This method works best when you're building a ferrocement house in an area where the ground freezes. You must dig a trench for a concrete footing wider than the intended foundation. A wall is built on top the footing and then backfilled with soil and a layer of gravel. A wire mesh–reinforced slab on top of the walls supports the house without much danger of frost shift.

Slab-on-Grade

• Use a slab-on-grade foundation where the ground doesn't freeze in the winter. This structure is simpler than a T-shaped foundation, poured thicker on the edges. Like all concrete foundations, a slab-on-grade type must rest on a bed of crushed gravel for proper drainage and must be reinforced with wire mesh and rebar. A slab-on-grade variant, the frost-protected slab, includes a wide bed of gravel and vertical insulation on the outside of the slab. This works only in heated buildings and prevents heat loss from the slab edge, keeping the ground around the house from freezing.

Stone Foundation

• Stone foundations are relatively uncommon in modern Western building, but are sometimes used by green builders or outside of the United States. Like concrete foundations, a stone foundation for a ferrocement house must extend below the ground and should be wider at the bottom than the top. Use larger stones lower in the structure. Avoid a very hard mortar, and check local codes to make sure that a stone foundation is permitted in your area. Include rebar or steel supports embedded in the foundation to begin your ferrocement wall structure.

Basements

• While most ferrocement houses are built on concrete slabs, some have basements. Dig a hole larger than the intended basement and add appropriate drainage around the walls to prevent leakage and other problems. Ferrocement houses are compatible with poured concrete, concrete block and precast panel basement walls. They do best when the reinforcing steel extends above the basement foundation, so that you can join the house walls directly to the basement.