Wood frame walls are load-bearing walls that carry the weight of the roof and floors down to the foundations. They may be interior or exterior walls.
Studs also provide space for insulation and surfaces to secure interior and exterior finishes. Some studs are load bearing, others are not. Bearing stud walls should have a double top plate. Non-bearing stud walls may have only a single top plate. A single bottom or sole plate is provided in either case. Incidentally, no matter how skillful a building expert is, he cannot determine whether a wood wall is bearing by tapping on it.
Stud Spacing
Historically, 2x4 studs have been used, spaced 16 inches on center, although more recently, 2x6 exterior studs have become common in energy efficient homes as they provide additional space for insulation between the studs. Metal studs are not used much on single family homes although they are common in commercial construction. Metal studs are usually non-load bearing.
Where an upward extension of the building is planned, special engineering consideration should be given, It may be that a conventional 2x4 wood-frame wall with studs 16 inches on center cannot safely carry a load imposed by a third floor addition. In lower quality construction, stud spacing may be 20 or 24 inches. This greatly restricts the ability to extend the building upwards, without stiffening the walls.
Common Problems
Inadequate nailing can lead to difficulties. Openings in walls may not be adequately framed. Wall sections above large openings for picture windows, for example, often sag if the openings are not bridged with appropriate lintels.
Buckling and Sagging
Some wood stud walls are susceptible to buckling under loads, particularly if the walls are not braced with girts (solid blocking near the mid point introduced horizontally between adjacent studs) or if interior or exterior finishes are not provided. If finish is provided on one side of the wall, girts are not required. An unfinished basement bearing wall with no girts may be susceptible.
Longer studs are also more susceptible to buckling. An easy way to understand this is to hold both ends of a yardstick and try to push the ends toward each other. The yardstick buckles very easily in the middle. This is more difficult to accomplish with a 6-inch ruler of the same material.
Openings in walls may not be adequately framed. Wall sections above large openings for picture windows, for example, often sag if the openings are not bridged with appropriate lintels.
Condensation Damage
Condensation damage to studs in exterior walls is becoming a concern, especially where insulation is being upgraded in older houses, and good interior air/vapor barriers on the warm side of the insulation are not provided. Since the process is largely concealed, it is difficult to spot during a visual inspection and may act for a long time before the damage is noticed. In some cases, peeling exterior paint will be one indication that wall condensation is a problem.
It should be understood that this is typically a seasonal problem, with the condensation occurring during the winter months only. Warm moist air enters the wall from the house. As it passes through, the air cools. Cool air cannot hold as much water as warm air. Condensation forms inside the wall as the air cools and gives off its water.
Low-Quality Lumber
Poor quality studs or studs that warp and bow shortly after construction can lead to unsightly wall surfaces in new construction. There is no easy answer to this problem. The bowed or twisted studs have to be removed and replaced.
Building with lumber which is too wet or "green" can result in problems such as shrinking, warping, or bowing. A moisture content of more than nineteen percent is considered too high for wood used in residential construction.
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