[RE-wrenches] to flash or not to flash

Brian Teitelbaum bteitelbaum at aeesolar.com
Thu Aug 6 12:03:39 PDT 2015


Jason makes an interesting point.



I also think that flashings should always be used, but bear in mind that
with asphalt shingles, and most roofing systems for that matter (membrane
roofing is one exception), the shingles themselves are not really the
“waterproof” part of the roofing assembly. The underlayment is.



The primary purpose of the shingles, and the flashings, is to shed the
majority of the water, and to provide physical protection for the
underlayment from the elements and protection from UV light degradation.
And of course for visual esthetics.



It’s very important  that the penetration through the underlayment be
sealed properly. I’ve always thought that the reason we don’t see more
leaks from L-feet on top of the shingles is because of the clamping
pressure from the lag bolt compressing the layers of roofing materials.
Water is a fairly thick fluid, and even though you can get capillary
wicking between the materials, it needs to be a relatively large gap for
the water to wick between the layers.



I think that the best way to seal roof penetrations is to mount the L-foot
or standoff directly to the underlayment, using a double sided butyl
material, or something similar that is compatible with the underlayment
material. Then the upward penetration of the L-foot or standoff through the
shingles should be flashed. Of course, this is not easy to do on a retrofit
job, but would be the way to go on a new roof installation.



Many roofers, especially in snow zones, are moving into using self-adhering
underlayments, which also offer better sealing of all of the nail
penetrations. Basically, it has a sticky butyl or asphalt-based layer in
contact with the sheathing, with a non-sticky top surface. This makes it
self-sealing to all the nail and screw penetrations.



Some roofing systems are even moving to the “rain-screen” idea, that being
that there is actually a gap engineered into the system between the
underlayment and the final roofing material. This allows any water that
gets past the top-layer roofing to have a clear pathway to drain down the
slope of the roof and out the edge of the eve. Furring strips are used to
give a 3/8” or larger gap. This also allows air flow into the roofing
system to aid is drying out any moisture that does enter. This also might
make the use of flashings less imperative, since all the true waterproofing
is at the underlayment level, not at the shingles of other final roofing.



Brian Teitelbaum

AEE Solar



*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Jason Szumlanski
*Sent:* Thursday, August 06, 2015 11:05 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] to flash or not to flash



If we are talking code, we should also point out how people are "getting
away" without using flashings and why AHJs are not requiring them. What I
have seen is that a fastener is not considered a "penetration." The
argument used frequently is that the thousands of screws that attach an
exposed fastener metal roof are not "flashed." The argument goes that the
codes sections cited be Andrew are intended for large openings like roof
vents and plumbing vents. If the screw occupies the space of the
"penetration" and is further sealed with sealant or a gasket, there is no
flashing required. You could extend this argument to shingle nails that go
through the "roof plane" depending on how you define it.



Don't kill the messenger - I'm just pointing out the logic/argument made
against the requirement for flashings.



I'll reiterate that my vote is to flash!



Jason



On Thu, Aug 6, 2015 at 1:04 PM, Andrew Truitt <atruitt at gmail.com> wrote:



Flash!  It provides a better, longer-lasting seal, and its a Code
requirement in most jurisdictions.  From the IBC via the Quickmount PV
website:



[image: Inline image 1]



If one chooses to attach a footing directly to the roof without an
integrated flashing then an "insurance option" is to install an 8"
step-flashing under the shingle course above the penetration.  This works
better for railed systems than railless since the whole footing assembly
can be covered by the modules.







For a brighter energy future,


Andrew Truitt

Principal
Truitt Renewable Energy Consulting, LLC

(202) 486-7507

LinkedIn Profile <https://www.linkedin.com/in/andrewtruitt>

Company Website <http://truittreconsulting.weebly.com/>

NABCEP Certified PV Installation Professional ID: 032407-66

Colorado Journeyman Electrician License No.: 600132











On Thu, Aug 6, 2015 at 10:47 AM, Daniel Young <dyoung at dovetailsolar.com>
wrote:

Writing the subject above, it seems like I’ve heard this question on the
wrench list before, but I could not find it in my old email archives. Feel
free to pint me back to the old discussion if it’s there.



I’ve been using a flashing based roof attachment for 8+yrs now (quick mount
or similar). Now we are looking at Rail-less systems  (quick rack is a good
example). There is also a non-flashed rail-less racking from roof-tech
http://roof-tech.us/ . I’ve always been of the opinion that simply crushing
some sealant/gasket onto an asphalt shingle work fine at first (the test
data from roof-tech is impressive), but would be an issue 10+yrs down the
road (thermal expansion movement, freeze/thaw, etc). I can make a good
waterproof seal at first by just slathering some butyl/silicone to an
L-foot and cranking it down on the shingles, but that practice really
disappeared 8+yrs ago.



Maybe consider this a Poll: (to flash, or not to flash)



With Regards,



Daniel Young,

NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90
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