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Interesting Facts About Product-Approved Roofing Materials and the Building Code

May 15, 2015

In Florida, where Roof Hugger does
a significant amount of retrofit roofing,
there is a system for product
approval. The state of Florida has
one system, and Miami-Dade has
another. Florida Product Approval
and a Notice of Acceptance are the respective
systems. Both require certain minimum
product test criteria to be used in the state.
Upon acceptance, a number—commonly
known as an “FL #” or an “NOA #” for the
new roofing material—is issued.
Building departments require the product
number be on the plans before a permit
can be issued—a well-intended practice
designed to protect the consumer. There is
one simple problem: Just because you have
an FL # or an NOA # does not automatically
mean that that product meets the Florida
Building Code (FBC)!
Florida Product Approvals for roofing
products give one the “limits-of-use” defining
maximum wind-uplift pressure resistance
for each tested product installed
in a particular way on a particular roof
substrate. Well, fine, but if the product has
an FL # and it is also UL-90 rated, then at
least it is good for 90-psf wind uplift—right?
No, not so. A UL-580 test places a particular
roofing product in a vacuum chamber;
draws a vacuum incrementally up to a
maximum of 105 psf; and, if the product/
assembly stays together, it passes the test
and can be UL-90 rated. Since the FBC and
many other design professionals require a
minimum “Factor of Safety” of 2.0, the product
will typically have a maximum usable
uplift load capacity of 52.5 psf (half of the
the 105 psf maximum).
Other roofing products employ tests
designed for their specific products in specific
assemblies. Each roofing material has its
own particular test protocol. For structural
metal roof panel systems, the most commonly
accepted industry tests are UL-580
and ASTM E1592 (Standard Test Method
for Structural Performance of Sheet Metal
Roof and Siding Systems by Uniform Air
Pressure Difference). E1592 tests use a larger
test sample, and they test the product/
assembly to failure. Failure can be fastener
pullout, seam/joint disengagement, deflection,
or roof clip failure. The sustained
pressure prior to the point of failure is then
divided in half, and that is the maximum
working uplift pressure that can be used in
design calculations. So if the panel system
fails at 125 psf and 120 psf was the highest
sustained test load, then a maximum of 60
psf may be used as the design load, assuming
deflection limitations are not exceeded.
So what does this all mean for designing
and permitting a new roof or a reroofing
project? This part is pretty straightforward:
If the FBC-required wind uplift loads on
a roof exceed the tested capacity of the
roofing material—even if the material is
Florida Product Approved—it does not meet
FBC. These same parameters apply to the
International Building Code (IBC).
So how does one know what the loads
are? It all starts with the American Society
of Civil Engineering’s ASCE-7 published
design criteria, which is an FBC-approved
engineering method that determines design
pressures in each of several different roof
“zones.” The size of these zones and the
minimum uplift pressure each zone must
resist is established by ASCE-7. On a simple,
low-slope gable building, there are three
zones: the corners (Zone III) are where the
loads are typically highest, the perimeter or
edges (Zone II) are where the loads are higher
but less than the corners, and the field
(Zone I) is where the loads are the lowest.
A simple low-slope roof plan would look
like Figure 1.
The ASCE-7-2010 loads
for an 80-ft.-wide x 150-ft.-
long x 20-ft.-high-eaved
building in Orlando, Florida,
at 136-mph wind speed,
under general occupancy, are
• Zone I: 25 psf
• Zone II: 42 psf
• Zone III: 64 psf
Let’s look at this building,
comparing two different FBCapproved
metal roof panel systems installed
on a pre-engineered building with 5-ft.
purlin spacing.
Panel System “A” is a new 24-in. trapezoidal
standing-seam roof with snap-together
seams. When we look up the “limits
of use” in the Florida Product Approval, we
find the following test values:
• Maximum allowable load: 22.5 psf
when attached to purlins 5 ft. o.c.
• Maximum allowable load: 52.5 psf
when attached to purlins 1 ft. o.c.
• Values between 1 and 5 ft. can be
interpolated per Table A.
This roof panel can only meet the lightest
loads in Zone I of the roof if additional
framing is added to reduce the clip/attachment
spacing to 4 ft. This is similar for Zone
II, except the panel must now be attached 2
ft. o.c. The bigger problem is that in Zone
2 6 • I n t e r f a c e J u l y 2 0 1 5
Figure 1
Sample PSF Uplift Resistance Values of Florida
Product-Approved Panels
Panel A Panel B
Purlin/Clip 24-in. Trap-Snap- 16-in. Mechanically
Spacing Together System Seamed System
5 ft. 22.5 47.0
4 ft. 30.0 66.5
3 ft. 37.5 86.0
2 ft. 45.0 105.5
1 ft. 52.5 125.0
Table A
III, the required load of 64 psf is beyond
the tested capacity of the panel: 52.5 psf
attached 1 ft. o.c. This panel cannot be used
on this project, even though it is Florida
Product Approved. See Table B.
For Panel System “B,” with the “limits of
use” using a mechanically seamed, standingseam
panel with 16-in. o.c. vertical ribs, we
find the following:
• Maximum allowable load: 47.0 psf
when attached to purlins 5 ft. o.c.
• Maximum allowable load: 125.0 psf
when attached to purlins 1 ft. o.c.
This panel can meet the 25-psf Zone I
loads on 5-ft. attachments and the 42-psf
Zone II loads on 5-ft. attachments. It can
also meet the 64-psf Zone III loads in Zone
III, but the attachment/purlin spacing must
be reduced from the existing 5-ft. spacing.
Adding the needed structure to reduce the
purlin spacing to 4 ft. provides 66.5-psf
capacity, making the product fully FBCcompliant.
All roofing materials—conventional and
metal—have similar limitations on their
use, and simply selecting a product that is
“approved” does not mean it is appropriate
or will meet the code-required loadings.
I have encountered products such as single
plies and TPOs that were rated to 130 mph
and beyond that were designed to be installed
over poured concrete or 20- to 22-ga. structural
metal decking and are being specified on
composite boards, plywood, or existing 26-ga.
metal roof panels. Similarly, metal panels
with capacities well below code requirements
are being specified for use just because they
have “product approval.”
When selecting a material for a new or
reroofing project, I recommend the following:
1. Find out what the required roof loads
are in each zone, as well as the zone
size and shape. Differently shaped
roofs will have different zone configurations.
Many suppliers will assist
with an “estimate” of these loads,
which is fine for budgeting, but consulting
a professional engineer is the
only way to ensure compliance.
2. Understand the “limits of use” for
the roofing product you want to
install. Make sure they exceed the
code minimums. Remember, each
product, although similar to another,
will have its own specific limits.
3. Make sure the building construction
is within the parameters of
the product approval limits of use.
If the building is outside of those
parameters, consult an engineer to
determine how to proceed.
4. Finally, when installing the product,
make sure it is installed exactly
as stated in the product approval
documents. Failure to follow the
installation guidelines may result in
a non-code-compliant assembly.
The FBC, the IBC, and the related
product approvals have set a high bar to
ensure strong, durable, high-quality roofs.
Understanding and following the details
and limitation of the approvals are keys to
achieving the intended results and keeping
a building code-compliant.
Over 60 Million Square Feet
Installed Since 1991
Benefits of
• Fast and easy to Install
• No more roof leaks
• No disruption to building operations
• Fits nearly all existing metal roofs
• Fully-engineered systems to meet
new code
• Can strengthen existing purlins
• Easy upgrade to standing seam roof
• Decreases energy costs
• ACad details & specs – LEED point
• Free design load and budget
is available by
calling or emailing
J u l y 2 0 1 5 I n t e r f a c e • 2 7
Dale Nelson is president
and owner of
Roof Hugger, Inc.,
a manufacturer
of retrofit framing
systems for metalroofed
founded in 1991
in Tampa, Florida.
He holds a Class-A
Florida Contractors’
License. He is
past chairman of
Pasco County Florida Committee of 100, and
a current board member of the S.E. Chapter
Metal Building Contractors and Erectors,
the Metal Construction Association, and the
Sertoma Speech and Hearing Foundation
of Florida, Inc. Nelson is a member of RCI
and the Metal Building Manufacturers
Dale Nelson
Review of Panels vs. Required Capacity
Code-Required Panel A Panel B
Roof Min. PSF Uplift Required Required
Zone Resistance Purlin/Clip Spacing Purlin/Clip Spacing
Zone I 25.0 4 ft. o.c. 5 ft. o.c.
Zone II 42.0 2 ft. o.c. 5 ft. o.c.
Zone III 64.0 Beyond Limits 4 ft. o.c.
Table B