www.mrca.org  —  Midwest Roofer
17
TECHNICAL & RESEARCH
membrane is suggested. When specifying tapered 
insulation, elevations should be checked using the 
maximum thickness used in the system. 
Low-set clerestory windows can provide pleasing 
sightlines, and mechanical, electrical and HVAC 
engineers may have solid reasons for wanting wall 
penetrations in certain places. These elevations must, 
however, also account for the specified thickness of the 
roofing system. Failure to do so may cause the roofing 
system manufacturer to not approve the warranty. More 
important, it will jeopardize the long-term performance of 
the roof and the building.
Roof Edge Design
In a list of the most important considerations when 
designing a low-slope roof, the roof edge comes in 
second, behind only roof slope.
The majority of roof failures are the result of metal 
edge failures in high-wind events. The Roofing 
Industry Committee on Weather Issues Inc.’s 2007 
report on wind-related roof damage caused by 
Hurricane Katrina backed this up, stating “Many 
examples of damage appeared to originate at 
failed edge details.” The report also offered the 
solution, saying “The main lesson learned appears 
to be that roofs designed and detailed according 
to current codes and standards will perform 
satisfactorily.”
Edge design is, therefore, not an area for cutting 
corners or pinching pennies.
Design professionals must not waver in requiring 
that all edge metal products meet ANSI/SPRI/
FM 4435 ES-1 “Wind Test Design Standard for 
Edge Systems Used with Low Slope Roofing 
Systems” standards, and should specify that all are 
manufacturer-provided, pre-fabricated products. 
Roofing manufacturers’ system warranties exclude 
edge metal that does not carry the certification. 
If standard-compliant products are not used, 
the building owner will forgo that edge-to-edge 
protection, and if a blow-off occurs because the 
edge metal fails, the roofing manufacturer will 
not be responsible for repairing or replacing the 
membrane.
Continuous cleats, or clips, are required on faces 
with dimensions of 4 inches or greater, and the 
materials should be at least one standard gauge 
thicker than the exposed metal. This is the new 
standard, and all manufacturers offer such 
products.
Copings can make a big impact on a building’s 
aesthetics, but design professionals must 
remember that they are not waterproof. 
Waterproofing comes from the roofing membrane 
installed over the parapet wall. Shop-fabricated 
copings must be fastened on both the outside and 
inside of the wall, and these penetrations of the 
membrane are leaks waiting to happen. Instead, 
design professionals should protect the integrity of 
the membrane by specifying standard edge metal 
or by choosing snap-lock-style copings.  
When covering exterior fascia, thicker metal should 
be used to prevent “oil-canning,” or a perceived 
waviness in the panel. The longer the span, the 
thicker the metal must be. That, of course, comes 
with a higher price tag. A more cost-effective option 
for longer spans is to use a combination of smaller 
face metals—24-gauge steel up to 8 inches long—
and fascia extenders.
Conclusion
When it comes to delivering a high-performance, 
durable and warranty-eligible low-slope roof, 
success does indeed lie in the details. Sufficient 
drainage, protective edge metal and properly 
flashed penetrations are all crucial. Getting those 
details right starts during the design process. The 
time and thought invested will be well-rewarded in 
fewer change orders, a higher-quality and faster 
installation by the roofing contractor, and a happier 
building owner.
Jim Flickinger is the architectural specification 
training manager for low-slope roofing 
manufacturer Mule-Hide Products Co., assisting 
design professionals with roof specifications 
and details. A member of the American Institute 
of Architects (AIA), the International Institute of 
Building Enclosure Consultants (IIBEC) and the 
Construction Specifications Institute (CSI), his 
decades of experience in inspection, training and 
installation of multiple commercial roofing products 
allows him to share actual field conditions with 
specifiers and contractors.

View this content as a flipbook by clicking here.