In a basement house, interior support is usually provided by wood or steel girders supported on wood or steel posts. Wood posts should be supported on wood or steel posts. Wood posts should be supported on pedestals and not be embedded in the concrete floor, where they may take on moisture and decay. Steel posts are normally supported on metal plates. The wood girders may sag. Sag is permanent deflection that can be noted especially near the middle of a structural member. Some sag is common in permanently loaded wood beams and is not a problem unless parts of the house have obviously distorted. Sag is usually an appearance problem rather than a structural problem. Some deflection is normal and about a 3/8 inch deflection in a 10- span girder is acceptable in design.


The sill plates, joists and headers rest on top of the foundation. Thus, they are exposed to moisture and are vulnerable to decay or insect attack, particularly if the basement or crawl space is very damp. Here too, some sag can be expected and is not a sign of structural damage. It is usually not a serious problem in floor joists unless the foundation system has settled unevenly, causing excessive deflection in parts of the floor system. Sag might be considered excessive if it is readily apparent from a visual appraisal of the levelness of a floor. A floor may be noted to be excessively springy when walking across it. This may be remedied by adding extra joists or girders to increase stiffness. Another point of particular concern is the framing of the floor joists around stair openings. Some builders estimate that 50 percent of the houses built have inadequate framing around stairs. Where floors are sagging, the framing will have to be carefully leveled and reinforced.


The usual stud wall normally has much more than adequate strength. It may be distorted, however, for reasons covered in preceding sections. Some adjustments are possible but large distortions will require new framing. Sag in headers over wide window openings or wide openings between rooms that is visually noticeable, may require new headers.


If the ridge line is not straight or the roof does not appear to be in a uniform plane, some repair may be necessary. The ridge will sag due to improper support, inadequate ties at the plate level, or even from sagging of the rafters. Rafters will sag due to inadequate stiffness or because they were not well seasoned. Sheathing sag may indicate too wide a spacing between rafters or, strip sheathing or plywood that is too thin or has delaminated.

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