Is it safe to buy a home with cement asbestos siding? Most cementious building materials are considered to be non-friable, and are probably less hazardous than other friable asbestos products such as asbestos pipe insulation.
Asbestos-cement products were developed in an era of ingenuity for creating easy to install and economic building materials. Although asbestos-cement has acquired a poor reputation by association of its title, it has not gained that reputation through a lack of durability or utility. In order to preserve this twentieth-century material, understanding what makes, or does not make, asbestos a hazard is truly important. In this case, no hazard is created when asbestos-cement building materials are sound and left in place, or when treatments incorporate non-abrasive means.
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| Asbestos cement wall shingles were in popular use in the U.S. from the 1920's (est) through the 1960's (est). A mixture of asbestos fibers and portland cement the material was durable and fire resistant. Siding materials that use fibers and aggregate other than asbestos are properly called "fiber cement" building siding products. Some manufacturers use the term "fiber-reinforced cement" for these products. All of these products use some sort of fiber along with cement. Before 1978 in the U.S. the common fiber used was asbestos
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| In this photo of a house in New York State we can see both original cement-asbestos wall shingles and newer fiber cement replacement wall shingles that do not contain asbestos. But only an expert or a lab can tell the new fiber cement from the old asbestos fiber cement shingles - or you can with help of the inspection and repair tips we provide below.
How can we tell the difference between asbestos-containing shingles and fiber-cement wall shingles?It's tricky. But here are some ways to distinguish between asbestos containing shingles and non-asbestos fiber-cement shingles:* Age or date of installation: installed before 1978 the shingles probably contain asbestos.
Layers of paint or finish coatings; the original shingles of both asbestos-cement and fiber cement usually come from the factory painted white on one side. Owners often painted cement asbestos
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shingle siding to make it look fresh, or if it was weathered and fuzzy, to preserve it. On a building that has has a portion of its original cement asbestos shingles replaced with newer fiber cement shingles, and where some original asbestos cement shingles remain, you'll see a difference in the thickness of layers of paint on the two materials. The shingle at the right in this photo clearly has fewer paint layers than the one at left. The left shingle is an older asbestos-cement shingle and the right photo is a new fiber cement shingle we installed.
If an asbestos-cement sided home has been re-modeled such as by adding a window or door, it's likely that the old asbestos cement shingles were broken around that new opening during the construction work - expect to see newer fiber cement shingles there.
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| The back of a new fiber cement wall shingle will probably have a code stamped on it such as we show here.
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| * The presence of old dirty demotion materials may suggest that old asbestos cement shingles have been removed from the home even when new, completely different materials are installed.
We found this cement asbestos siding debris on the ground around a home that boasted new vinyl siding.
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* The presence of multiple layers of exterior siding can be spotted by noticing that the wall cladding extends out past the original window or door trim. But beware; when we renovated the building shown above we built-out the exterior trim so that it would continue to project beyond new vinyl siding installed on some wall surfaces.
* The nails used to secure the shingles probably won't help unless some are obviously different from others; installers use the same galvanized box nails to hang these shingles as they did in 1955.
Planning demolition of cement asbestos siding or shingle siding materials?
The risk of high levels of airborne asbestos from cementious products is probably very low unless the workers are using power equipment like sanders and saws on these substances.
Using cement asbestos roofing products as an example, according to NRCA, the National Roofing Contractors' Association, their studies up to February 1992 had not found a single roofing job at which these limits were exceeded, and NRCA reported that in some cases no fiber release was detected. But it appears that the association may have been referring only to asphalt-based roofing materials, not jobs involving the demolition of other ACRM such as cement-asbestos roof shingles (or "asbestos roof tiles" as some consumers refer to them) which might produce different statistics.
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