Q&A: Shingling Over Tar and Gravel

A.The best way to remove the old roofing would be with a “power spudder.” But if the roof is steep enough for asphalt shingles (3/12 or more) this machine would be too dangerous to use. In this case, you might try scraping off as much of the gravel as possible and installing a new roof deck — either plywood or OSB — over the existing roof. This sheathing should be nailed to the rafters, unless a thick, solid wood deck was originally installed. Asphalt shingles can then be installed over the sheathing. First, find out if the roof framing can support the added weight. But if a lot of gravel is removed, the weight of the new roof may not increase the load enough to matter.