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Abstract
The built-up membrane has three basic components: felts; bitumen; and a surfacing of bitumen with or without aggregate. It forms a semi-flexible weatherproof covering made with as little as two or as many as five plies of felt, custom-built to fit the contours of the deck. The felt reinforcement is either organic (felt papers, rags and shredded wood fibers) or inorganic (asbestos or glass fibers). It has been the practice in the roofing industry to specify the number of plies used in a built-up roof according to the service life desired, for example: 10 years - two felts and three layers of bitumen; 14 yrs - three felts and four layers of bitumen; 20 yrs - four felts and five layers of bitumen. Some construction agencies of the U.S. government permit the substitution of asbestos- or glass-base felts for organic felts on a ply-for-ply basis. However, the substitutuion of glass felts on a one-ply-less basis is permitted in some cases as a result of information developed during an NBS field survey as reported in NBS Report 6966. Because of the interest in establishing a criterion for selection of the number of plies of any given felt, and because of the request of a manufacturer of asbestos felt that such a felt be specified on a ply-for-ply basis with glass felt and on a one-ply-less basis with rag felt, the NBS was asked to study the performance of asbestos-base built-up roofs as part of the Tri-Service Building Investigation Program.
The built-up membrane has three basic components: felts; bitumen; and a surfacing of bitumen with or without aggregate. It forms a semi-flexible weatherproof covering made with as little as two or as many as five plies of felt, custom-built to fit the contours of the deck. The felt reinforcement is either organic (felt papers, rags and shredded wood fibers) or inorganic (asbestos or glass fibers). It has been the practice in the roofing industry to specify the number of plies used in a built-up roof according to the service life desired, for example: 10 years - two felts and three layers of bitumen; 14 yrs - three felts and four layers of bitumen; 20 yrs - four felts and five layers of bitumen. Some construction agencies of the U.S. government permit the substitution of asbestos- or glass-base felts for organic felts on a ply-for-ply basis. However, the substitutuion of glass felts on a one-ply-less basis is permitted in some cases as a result of information developed during an NBS field survey as reported in NBS Report 6966. Because of the interest in establishing a criterion for selection of the number of plies of any given felt, and because of the request of a manufacturer of asbestos felt that such a felt be specified on a ply-for-ply basis with glass felt and on a one-ply-less basis with rag felt, the NBS was asked to study the performance of asbestos-base built-up roofs as part of the Tri-Service Building Investigation Program.
Date
2/1969
2/1969
Author(s)
Boone, Thomas; Skoda, Leopold
Boone, Thomas; Skoda, Leopold
Page(s)
17
17
Keyword(s)
asbestos, asbestos felt built up roof; asbestos fiber; asbestos felt
asbestos, asbestos felt built up roof; asbestos fiber; asbestos felt