Performance Approach to the Development of Criteria for Low-Sloped Roof Membranes.
Performance Approach to the Development of Criteria for
Low-Sloped Roof Membranes.
Rossiter, W. J., Jr.; Frohnsdorff, G. J. C.; Masters, L.
W.; Martin, J. W.
NISTIR 4638; 36 p. July 1991.
Available from: National Technical Information Service
Order number: PB94-160751
evaluation; low-sloped roofing; membranes; performance
criteria; requirements; roof functions; roofs; seams;
test methods; watertightness
This report outlines a performance approach for
developing criteria for the selection and use of
membranes in low-sloped roof applications. An overview
of previous efforts for applying the performance
approach to membrane roofing is also given. A
fundamental aspect of the performance approach is that
selection criteria are based on an understanding of the
requirements necessary for the membrane system to
perform acceptably in service. The availability of
performance-based criteria would greatly assist in
eliminating some of the defects that have plagued
low-sloped roofing over the years. The approach
consists of seven steps including identification of the
key functions to be performed by a roof, identification
of attributes essential to satisfactory performance,
development of the requirements, criteria, and test
methods, and putting in place a feedback mechanism to
revise the criteria, if warranted, as new information
becomes available on the performance of the system in
service. Five key functions associated with the
performance of the membrane in a low-sloped system are
identified, and performance requirements for each
function are proposed. These functions are
watertightness, maintainability, health and safety,
environmental impact, and appearance. Of these five
functions, watertightness is the one that directly
affects the major problem (i.e., leaks) associated with
low-sloped roof performance. As a consequence, the
majority of the requirements recommended for membrane
systems in past studies, as well as in the present
report, emphasize this aspect of performance. It is
recognized that considerable effort may be needed to
develop criteria and test methods for the complete set
of attributes. Consequently, the initial work should
focus on those attributes of membrane roofing that have
been associated with the most problems. Review of data
from NRCA's Project Pinpoint indicated that seam defects
in single-ply membranes have been the problems most
frequently enountered for these types of roof systems.
On this basis, it is further suggested that the
application of the performance approach to membrane
roofing begin with the subject of seams. As an initial
step in this direction, an outline of the needed
criteria is presented including attributes and suggested
requirements. The development of criteria and test
methods are reserved for future study.