continued waterproofing integrity suggests an excellent
return on initial investment, meriting the serious consideration of any owner expecting to hold onto a property for 25
years or more.
Three Must-Dos for Extending Service Life
If extended service life is an appropriate goal for your roof, there is
much you can do to improve your odds
of long-term success. The three roofs
studied have effectively doubled the
life span expected of today’s commercial roof offerings thanks to these three
1) Specifying quality materials.
All three roofs were on manufacturing
buildings with higher-than-average
foot traffic, which required systems
with high puncture and tear resistance. Given the thermal variations in
Indiana, a membrane with a generous
safety margin in regards to elasticity
and a reinforcing fabric with significant tensile strength were appropriate.
In all three cases, the owner chose a
bitumen blend of SBS polymers with a
mixing process that ensured uniform
dispersion, plus a high-performance
scrim that added tensile strength several times greater than
the industry standard in the early 1980s when the roofs
However, the membrane only tells part of the story.
The specifications also called for a comparably high level
of quality in all other system components, including two
courses of insulation, multi-layered construction, a high-performance waterproofing cap sheet, and a belt-and-suspenders flood coat of gravel surfacing. Some may call
these specifications over-engineered, but in my mind, the
sustained performance of such redundant systems is attributable in no small part to the quality of the materials used.
2) Vigilant monitoring during installation. The
highest quality materials can still result in a premature
roof failure if they are improperly installed. Ensure
every system component is added in full compliance
with the specification and the manufacturer requirements. This means vigilant job site monitoring during
construction is recommended – in the case of these
roofs, this task was performed by a representative of
the membrane manufacturer responsible for warranting
3) Long-term preventive maintenance. The final
element indispensable to extending roof life is proactive
maintenance. Roofing success is a responsibility shared
by the building owner. No homeowner would expect
a roof to survive multiple freeze-thaw cycles without
cleaning out roof gutters periodically, and the typical
commercial roof experiences far more foot traffic,
exposure to potential punctures and tears, and degrees
of building movement. Commercial roofs also support
far more roof equipment, making preventive maintenance vital to long-term performance.
The owner of these three roofs collaborated with his
roofing partners across decades for ongoing inspections
of flashings, gutters, drains, and other critical components
while diligently performing any required minor repairs. As
a result, all three exceeded their warranted performance.
There can never be one single roof system application that solves every problem, but this approach to
roof system selection, installation, and maintenance has
already proved successful and cost-effective. If owners
are to ever achieve a roof service life that lasts as long as
the building itself, they must move forward grounded in
these principles. B
Dr. Heshmat O. Laaly is an analytical research chemist,
professional roofing consultant, and president of Roofing
Materials Science and Technologies in Los Angeles, CA. He
is also the author of Science and Technology of Traditional
and Modern Roofing Systems. For more information, see
THIS FOUNDRY ROOF,
bitumen cap sheet.
INTEGRITY of this modified
bitumen roof was laboratory
tested after 25 years of service.
It retained 80% of its tensile
strength while maintaining low-temperature flexibility and compound stability well within the
requirements of ASTM D6163.