Wood Frame Construction

Almost all houses in California are wood frame structures. Wood frame structures are built with light wood studs and joists. The walls are typically constructed from 2 x 4 or 2 x 6 studs spaced 16" to 24" apart. These walls sit on top of the foundation and support upper floors and the roof. Plaster or gypsum wallboard is attached to the studs to form the interior finish. The exterior finish may be wood or metal siding, brick facing, or stucco plaster. New wood frame houses are required to resist earthquake forces, so some of the walls are usually constructed with sheets of plywood nailed to the studs behind the exterior finish.

The typical wood frame roof is constructed with 2 x 6 or 2 x 8 rafters spaced 16" to 24" apart. Roof sheathing (boards in older structures, plywood in newer buildings) is nailed to the top of the rafters, and the roofing material (shingles, shakes, tile, or built-up roofing) is applied to the top of the sheathing. The floors are usually constructed with 2 x 10 joists spaced approximately 16" apart. The floor sheathing, similar to roof sheathing, is nailed to the top of joists (see Figure 1 for an illustration of a typical wood frame building).

Sometimes a wood frame building may look like it is made from masonry or concrete. Most commonly mistaken is the stucco building. Stucco is portland cement plaster applied over wire mesh. Nearly all stucco houses are woodframe structures, although the stucco conceals the wood framing. Stucco is used as an exterior finish because of its durability; however, since stucco may not contribute to the strength of the house, stucco houses are not necessarily stronger than other wood frame structures. To determine whether there is a wood frame under the stucco, knock on the wall from the outside---the wall will sound hollow.

Another example of a disguised wood frame is the building with veneer. Exterior siding can look like metal or masonry; for example, there is an asphalt siding that looks like brick. To determine whether a building is wood frame, knock on the siding-it will sound hollow. Sometimes, wood frame buildings have a real masonry veneer which can "peel off" in earthquakes. If you have such veneer on your house, contact an architect or civil or structural engineer for a detailed investigation.

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