Basic House Construction Techniques

Foundation

• Residential homes usually rest on either a concrete slab foundation or poured concrete or concrete block walls. All of them sit on top of footings, sections of poured concrete that lie on the soil horizontally. Workers create poured concrete foundation walls by placing cement in molds, and then removing the molds when the cement hardens. Block walls are joined together with mortar. Slab foundations usually sit directly on the ground and measure about 4 to 6 inches thick.

Floor and Walls

• Although it's possible to place a floor directly over concrete, builders usually create a raised floor by attaching framing members called joists to the large beams, or sills, that rest on the foundation. Plywood subflooring goes on top of the joists and supports the finished floor. Wood studs, normally 2-by-4s, are spaced 16 inches apart between the sill and the top plate, a beam that spans the top of the wall, to create the exterior wall framing. Drywall is then nailed to the studs on the inside of the wall.

Roof

• After ceiling joists have been nailed to the tops of the walls, the roof framing is placed over the joists. Roof framing can consist of individual planks called rafters, but more recently, using trusses, or units of triangular framing members, has become a standard method of construction, as well. Once the rafters or trusses are attached to the joists or top plate and the ridge pole, the long beam that spans the length of roof at the top, the application of felt, sheathing and shingles finishes the job.

Siding

• A protective membrane such as builder's felt and insulation cover the plywood sheathing on the outside of the exterior walls, and then the siding material, such as clapboards, vinyl siding or wood shakes, is applied. In some cases, rigid panels of insulation might take the place of the plywood sheathing. The panels, called house wrap and made from a polymer material, help keep the house warm by keeping air from penetrating through the walls.