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2018 National Home Improvement Estimator, All Rights Reserved Page 58

Defects in the Roof
Roof leaks are usually caused by a failure of the roof cover, and can lead to rot damage to both the
sheathing and the rafters. It would be poor practice to replace roof cover without making repairs to a
sagging or decayed roof deck. Unlike problems with floor joists and floor beams, nearly all roof framing
problems can be repaired economically. See Figure 4-9. Examine the roof for sagging at the ridge,
rafters and in the sheathing. A ridge board can sag due to improper support, inadequate ties at the plate
level, or even from sagging rafters. Rafters sag if the lumber wasn’t well seasoned or if the lumber didn’t
have enough strength for the span. Sheathing sag is the result of rafter spacing that’s too wide or
sheathing material that’s too thin. Occasionally, plywood sheathing will de-laminate and lose
load-carrying capacity.