01 May 1999
SHATTERING OF AGED UNREINFORCED PVC ROOF MEMBRANES
(A Joint Document from the NRCA and SPRI)
This document is based upon information developed through a survey conducted by the National
Roofing Contractors Association (NRCA) in an attempt to clarify the incidence of shattering of
unreinforced polyvinyl chloride (PVC) roof membranes. In an effort to educate professional roofing
contractors, building owners, architects, engineers, roof consultants, sales representatives, material
distributors and suppliers, and others with the latest available information on the subject, NRCA and
the Single Ply Roofing Institute (SPRI) have developed this joint document, which includes the
1. Description of the Shattering Phenomenon
2. Membrane Identification
3. Early Warning Signs
4. Cold Weather Precautions
Building owners with an unreinforced PVC membrane roof should determine the manufacturer of the
membrane. The manufacturer should then be consulted for specific information regarding
maintenance and modifications. If the manufacturer is no longer in business, a professional roofing
contractor or qualified individual knowledgeable about the installation and maintenance of PVC roof
membranes should be contacted.
There is no evidence that shattering occurs in reinforced or fiber
supported PVC membranes (see definition in Section 2). Reinforced
or fiber supported membranes are the type of PVC membranes that
are now commonly installed.
If the roof membrane is under a manufacturer's warranty, the building owner should consult the
manufacturer for specific information.
The building owner should be aware of warranty terms and conditions
in order to prevent voiding the warranty inadvertently. For example, a
warranty may indicate that repairs, alterations, or additions performed
without prior approval of the manufacturer will cause the warranty to
become null and void.
The following information reflects current knowledge as of September, 1990.
1. Description of the shattering phenomenon
"Shattering" is characterized by a generalized nonlinear fragmentation of the membrane. Each
fragment may be a few square feet or a few hundred square feet in total area. Typically, when a
shatter occurs, it extends throughout the entire roof area, from one edge or perimeter to the other, and
is judged to be nonrepairable. This condition is contrasted with cracking and splitting, which are
Cracking: Localized, nonlinear repairable separation of the membrane, with branches.
Splitting: A single, linear, repairable separation of the membrane.
Cracking and splitting are not addressed in this document.
Shattering may occur suddenly and prior to the onset of noticeable preconditions that warn of the
potential for shattering.