was applied below its EVP. This is evident by the smooth surface
of the asphalt which is indicative of lack of transfer between the
asphalt and the adjoining layer. Also noted in Figure 4, proper
inter-ply adhesion would be expected to cause some delamination of the insulation.
With fully adhered single ply membranes the attachment of the
membrane to the roof is adhesive. The condition of the substrate
plays an important role with respect to how well the membrane
is attached. The substrate should be clean and free of dust, and
debris, or materials not compatible with the adhesive. The ‘
Achilles Heel’ of a fully adhered single-ply membrane, however, is the
edge attachment. Once the edge is compromised by wind,the system has little resistance to the wind that is now under the membrane and the peeling action of the combined pressure.
Figure 5 shows a roof located in the Gulf of Mexico that failed
during a storm that produced wind velocities well below the applicable code required velocities. Inspection of the perimeter
condition (Figure 6) revealed that an inappropriate termination
bar was used to fasten the edge of the membrane to the parapet.
In this case, the flat bar had little clamping ability to adequately
hold the edge of the membrane. In effect, the edge of the membrane was only attached at the fasteners and not continuously as
is the intent of the termination bar.
Limits of technology
The requirements of a roof system are many, and are depen-
dent on region and function. Locally adopted building codes
and other criteria narrow the search for an appropriate system.
Manufacturers then go to great time and expense to have their
products rated as appropriate for use in a particular applica-
tion. This long, involved process requires input from designers,
code officials, contractors, and manufacturers. This process is
all for naught, however, if the intent of the design is not fulfilled
in the field during installation of the roof. How does one ensure
that the roof is properly installed in the first place? The answer
is through proper procurement and quality control, the discus-
sion of which is entirely outside the scope of this article. The
technology does exist to attach a roof to a building to withstand
a design event but when determining causation after a loss, it
is important to be mindful that the technology does not always
make it to the roof. K
David P. Amori, PE, RRC, is the senior district manager at EFI Global,
Inc. He may be reached at 210-682-4480, david_amori@efiglobal.
com, or www.efiglobal.com.
1 Hurricane Ike: Nature’s Force vs. Structural Strength, Institute for Home and
Business Safety, Sept. 2009
2 International Building Code, International Code Counsel
3 Asphalt Roof Manufacturer’s Association, ARMA Residential Roofing
4 The Roofing and Waterproofing Manual, 5th Edition, National Roofing
Contractors Association, 2003