- Author
-
Rossiter, W. J., Jr.
|
Denchfield, R. D.
- Title
- Observations From a Field Study of the Performance of Polymer-Modified Bitumen Roofing.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
Denchfield Corp., Silver Spring, MD
- Report
-
NISTIR 4972,
January 1993,
41 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
roofs
|
building technology
|
field study
|
low-sloped roofing
|
membranes
|
performance
|
polymer-modified bitumens
|
standards development
- Abstract
- The use of modified-bitumen membranes for low-sloped roofing in the United States has increased greatly over the last decade. In spite of this growth, voluntary consensus standards to aid in the proper selection and use of these membrane materials are not available. Moreover, few reports describing performance in service have been prepared. The two primary modifiers currently used to produce modified bitumens are: atactic polypropylene (APP) and styrene-butadine-styrene (SBS) block copolymer. This report presents the results of a field study of polymer-modified bitumen roofing. Observations on in-service performance are beneficial for identifying field problems that require study to attain solutions. Fifty-three roofs, ranging in age from 24 to 131 months and located in Washington/Baltimore, Jacksonville, Florida, and Dallas, Texas, were inspected. The types of membrane modifiers were almost equally distributed between APP and SBS polymers. Reroofing predominated the type of construction and was divided somewhat evenly between tear-off and re-covering. The overall performance of these relatively young roofs was considered to be satisfactory. About 70 percent of the roofs were considered visually to be in fine condition. Still, about a quarter of the roofs showed some defects that contributed to a lowered performance ranking. The key defects observed with some membranes were surface cracking of both APP and SBS sheets, loss of granules (particularly in ponded water), slippage of SBS sheets, and unsealed or relatively extensive repairing of the laps of an APP system. Although limited, the field experience provide evidence that performance-related standards are needed to evaluate the membrane materials' ability to resist such defects and to minimize future problems.