Vinyl siding, indeed, can go over asbestos

Inspector's Eye

January 20, 2002|By Dean Uhler

Melvin Rice of Baltimore asks whether it's better to remove or to side over the asbestos shingle siding on his house when vinyl siding is installed. Half of the contractors he's talked with recommend removing the shingles, but the others say to leave them and side over.

Asbestos-cement shingle siding is common on houses built or re-sided from the 1940s generally through the 1960s. In general, it was a very successful siding material and continues to perform well on many houses.

As it ages, the factory finish deteriorates, but even then the shingles can be painted. So, when new siding is installed on houses having asbestos-cement siding, it's usually done to improve or update the appearance of the house and not because the shingles are worn out.

Although asbestos-cement shingles contain asbestos, a carcinogen, they are considered nonfriable and are not regulated as a hazardous material as long as they are not crumbled or reduced to powder.

Siding shingles are nonfriable because the asbestos fibers are held in place by a cement binder in the shingles.

But damaging the shingles can release some of the fibers. So, whether the shingles are to be sided over or removed, the methods used should avoid breaking, cutting or abrading the shingles. Some experts recommend screwing, rather than nailing, when new siding is installed over existing asbestos-cement siding.

If the shingles are to be removed, they should be wetted during the process to prevent fibers from becoming airborne, and they must be properly disposed of at a landfill.

There appears to be no overriding advantage to either removing the shingles or leaving them in place. There may be a benefit to having a layer of tough, fireproof asbestos-cement shingles under the new lightweight siding.

One area where leaving the old shingles in place could be impractical is where exterior trim projects just barely beyond the face of the existing shingles.

Inspector's Eye

Dean Uhler has been a home inspector for more than 12 years and is president of Baltimore-based Boswell Building Surveys Inc. Uhler is a member of the American Society of Home Inspectors (ASHI) and is the treasurer of the Greater Baltimore Chapter of ASHI.

Questions, with name, address and daytime telephone number, about homes and home inspections can be faxed to 410-783-2517, e-mailed to or mailed to Inspector's Eye, Second Floor, 501 N. Calvert St., Baltimore, Md. 21278-0001.

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