Foundations and Floors

Patricia Skinner  |  1/3/2007 7:04:58 PM

A good home construction project begins with a firm foundation, which includes both the soils at the building site and the structures you place in or on that soil to help support the home. In much of South Louisiana, the soil provides a poor substrate and must be removed and replaced with soil that is less expansive and more capable of being compacted. Where the soil is unworkable, local codes typically require the use of pilings to support the foundation, even when the foundation is to be slab-on-grade.

Because Louisiana is prone to flooding, many homes need to be built on elevated foundations so the lowest floor is above anticipated flood levels. The flood-damage-prevention ordinances specify the types of foundations that can be used in different flood hazard areas. In areas where floodwater is fast-moving, the foundations must be open and professionally engineered. In other flood hazard areas, the foundations can obstruct the flow of water. In all cases, the structure must be anchored to resist flotation when floodwaters rise. Homes in high-wind areas must have foundations (and walls and roofs) that resist uplift.

In addition to supporting the structure, the foundation provides a bridge between the exterior walls of the home and the ground. Thus, it is the first line of defense for protecting the structure from native and Formosan subterranean termites. Three types of termite protection are recommended in combination: chemical barrier applied to the soil; physical barrier (steel wire mesh) between the foundation and the walls and at plumbing penetrations of a slab; chemical treatment of all structural wood in exterior walls and roof. Great care must be taken to avoid creating spaces or material "bridges" through which termites can pass undetected from the ground up to the walls, floors and roof of the home.

Floors carry the weight of occupants, furnishings and interior non-load-bearing walls. Many homes in Louisiana have slab floors, which can be either be exposed (patterned and stained) concrete or covered with carpet, vinyl, paving brick, tile or other material. 

Many homes have elevated floors, which are usually built of a series of beams and joists with a wood subfloor. Engineered, prefabricated floor joists are available. Insulating raised floors is a challenge that becomes greater as the distance between the ground and the floor becomes less and the level of the water table rises. It is extremely important to control moisture beneath the home and to avoid trapping moisture on wooden support structures.

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