different systems have varying degrees of factory vs. field fabrication. The contractor should have the expertise necessary to install
a given system.
It can be tempting for owners to overemphasize the importance
of warranties when they are narrowing their roof options. However,
as important as they are, warranties are not a guarantee of performance. I’ve been in the industry for 40 years, and I have never seen
a warranty keep water out of a building.
Jerry Beall is a Product & Technical Specialist at
Seaman Corporation’s Fiber Tite roofing division.
For more information, watch a free roofing webinar
entitled “ 5 Critical Roofing Performance Considerations” presented by Jerry at www.buildings.com.
He can be reached at firstname.lastname@example.org.
(Top) UV light has
on this bituminous
(Left) Lab tests
can provide useful
roofing data but
they are no
evaluating real-world weathering.
(Below) UV light has
broken down the
stabilizers in this
MATERIAL FACTORS FOR HIGH PERFORMANCE
A safe and long-lasting roof must provide solid resistance
to the following inescapable factors:
1) Ultraviolet light UV is the No. 1 enemy of asphaltic and
modified bitumen roofs. Both need some kind of granular
surfacing or cap sheet to protect the underlying membrane
from UV, whereas EPDM membranes resist UV very well.
The stabilizers for heat and fire in TPO membranes (and to a
lesser degree in PVC membranes) degrade their UV resistance, and manufacturers continue to work on a performance
balance. KEE membranes have excellent UV resistance and
stabilization due to their versatile polymeric engineering.
2) Punctures and impact Due to their mass and surface
aggregate, built-up roofs can have good puncture resistance
but it degrades over time. Modified bitumens have similar
puncture performance. Reinforcing fabric in single-ply membranes provide impact strength. Because of their densely
knitted reinforcement, KEE membranes offer very good
inherent resistance to impact and punctures.
3) Chemicals Whether you can see them or not, chemicals attack all roofs. These include chemicals from upwind
vegetation, aircraft fuel, and pollutants in rain, which can
turn into chemical soup when ponding. Asphalt has limited
resistance to greases, fats and oils; TPOs and EPDMs offer
selective resistance to some chemicals. Flexible PVC can be
challenged by chemicals that cause plasticizers to migrate.
KEE membranes compliant with ASTM D6754 inherently
4) Wind uplift To resist wind damage, proper engineering
is critical for each attachment option: adhered, ballasted
and mechanically attached. My personal preference is mechanically attached, but all methods can perform well when
5) Fire Roofing assemblies (rather than membranes alone)
receive fire ratings. That said, membranes have varying fire
resistance. Modified bitumens and EPDMs need special
flame retardants to meet UL requirements; TPOs have poor
resistance. Asphalt has some resistance, particularly on
low-incline roofs. KEE and PVC membranes provide excellent fire resistance.