01 May 1999
Based on the data obtained through the survey, shattering appears to:
Be related to aged unreinforced membranes, the majority of which were ballasted (see Section
Occur most frequently in cold weather.
Be unrelated to membrane thickness.
Have a median roof age of 8-1/2 years, with a range of 4 to 13 years.
Information gathered to date indicates that only a relatively small number of unreinforced PVC roofs
have experienced shattering.
2. Membrane identification
It is important for the building owner to know whether an unreinforced PVC membrane is on the roof,
so that proper precautions and maintenance procedures may be followed.
Unreinforced PVC roof membranes are defined as those containing
no internal fabrics or supporting fibers.
If the owner does not have historical records that identify the type of membrane, a professional roofing
contractor or qualified individual knowledgeable about the installation and maintenance of PVC roof
membranes should be contacted to identify the membrane.
Professional roofing contractors and qualified individuals should
consult with the manufacturer of the membrane for specific
recommendations and guidance regarding membrane identification,
maintenance, repair, new penetrations, or reroofing. If the
manufacturer is no longer available, the contractor should consult with
another PVC manufacturer.
Investigations should not be performed in cold weather (see section 4).
3. Early warning signs
Shattering may occur without warning. However, early warning signs may sometimes be present.
The early warning signs discussed below do not necessarily indicate
the roof will shatter. It is also important to note that at this time, no
reliable method exists to predict whether any one given roof may or
may not shatter.
Embrittlement: "Embrittlement" describes a condition wherein the
membrane has lost flexibility.
Displaced Wood Nailers, Base Flashings or Metal Flashings: Wood
nailers, base flashings or metal flashings that have pulled away from
their initial position may be indicative of high membrane stress or
building movement. A membrane under high stress may appear to be
PVC roofs, like all roof systems, should be inspected twice a year. At the time of these normal
inspections, the presence of the warning signs noted above should be determined. Inspections should
occur in the spring and fall, when the ambient temperature falls within the guidelines listed in Section