Getting at odd noises from a reroofing job

Q Last fall we replaced our 30-year-old cedar-shake roof with a standard plywood sheathing covered with fiber-glass shingles. We also replaced the gable louvers and added roof vents to ensure sufficient passage of air for a large attic fan. Not long after completion, we began to hear cracking and scurrying overhead, which was bewildering. The builder said nothing was amiss structurally. During the winter, the noise eased almost entirely; however, the noises now have returned. No rodents are involved. What is causing the noise and how can we get rid of it? Carolyn B. Wicker Stony Brook, N.Y.

A Obviously, the condition that causes the noise is something involved in the reroofing process. Recheck the adequacy of the attic louvers and vents to handle not only the attic fan air-exhaust volume but also to relieve the expanding air when it becomes heated in warm weather.

When hot, attic air expands, and this could cause the creaking, especially since inadequately vented attics in hot weather can result in cracks in plastered ceilings below.

The additional plywood sheathing and perhaps the new roofing may be heavier than the old wood-shingle roof, which was likely on spaced sheathing. The extra roof load could induce framing deflection, which, in turn, could make the rafters crack or pop as they settle, or as they are ''pushed'' by expanding or contracting attic air.

What to do now? After checking that the vents are more than adequate to do the job, install some additional bracing, vertical or diagonal, between or among the attic framing members. Such bracing might compensate for the additional roof loading in the reroofing process.

Elimination of the noises may take some ingenuity by a carpenter who is perceptive enough to detect not only the cause of the noise, but precisely where in the framing it is occurring.

Let us know the results of your efforts and just what those remedial efforts include.