DEAR BARRY: The home we are buying has a new asphalt shingle roof. It was installed by the seller over the old wood shingles. Our home inspector says this is a substandard installation, but the roof did not leak during recent rains. The seller says, "Take it or leave it." What do you think about asphalt shingles on wood shingles? Is this a code violation? –Jeff

DEAR JEFF: Your home inspector was correct in describing this as a substandard installation, although it may not violate any specific code requirements. However, a building permit is required when installing a new roof. If the seller did not take out a permit, that in itself would be a code violation, regardless of the quality of installation. Therefore, you should request that the seller provide documentation of municipal approval for the new roof. If the work was not permitted, you can request that the seller apply for an as-built permit to ensure that the installation complies with applicable standards.

The problems with asphalt shingles installed over wood shingles or wood shakes are as follows:

1) When wood shingles or shakes are ready for replacement, they are old, worn and brittle. When asphalt shingles are installed over this degraded surface, the nails do not provide secure attachment because they are fastened to material that is soft, cracked, thin and deteriorated. With compromised nailing, wind damage, detachment and leakage are more likely to occur.

2) Asphalt shingles are heavier than wood shingles. If the roof framing is designed to carry the lighter weight of wood shingles, the extra weight of asphalt shingles can cause the roof rafters and the ridge to sag. When changing to asphalt-shingle roofing, reinforcement of the roof framing may be necessary.

3) When asphalt shingles are installed over wood shingles, attic ventilation is reduced. Air passes freely through the gaps between wood shingles, but asphalt shingles thoroughly seal the roof surface. Reduced ventilation means that the attic will be hotter during warm weather, and heat exposure shortens the life of asphalt shingles. Therefore, when changing to asphalt-shingle roofing, additional roof vents may be needed.

4) Homeowners insurance companies may not cover leak damage if asphalt shingles are installed over wood shingles. Exclusions of this kind are often embedded in the fine print of insurance policies.

The only reason to install asphalt shingles over wood shingles or shakes is to save time and money. Sometimes this is done by homeowners who are unaware of roofing standards. Unfortunately, there are roofing contractors who should know better but who are willing to perform this kind of work. These contractors are competing for jobs and hoping to submit the winning bid. Instead of lowering their professional standards in this way, they should educate their customers by explaining the reasons for removing the wood shingles, adding new decking, and installing additional vents. If homeowners are willing to sacrifice quality for price, a contractor can submit two bids, one for each type of installation, while advising against the substandard method.

The seller is free to declare "Take it or leave it," but if the roof was installed without a permit, disclosure of that shortcoming is required.

To write to Barry Stone, please visit him on the Web at


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