Hi William;
First, a sealed L foot is not a sealant only attachment system. It has
quite a bit of surface area beyond the hole just like a flashing, and
has mechanical attachment through the roof to the structure (which a
flashing often does not). I consider an L foot to be a mini flashing for
a mini penetration. Its relative. A propanel screw has a 1/2" rubber
washer for a 3/16" screw, and is accepted by the roofing industry and
IBC. A 2" x2" L foot base with a 5/16" high strength lag and sealant
is much more seal relative to the penetration. A 12" x 12" flashing is
used for penetrations as large as 4" plumbing vents, and depends on the
rubber Oatey boot to seal, which most of us know will dry rot in 5-10
years. It's accepted by the roofing industry too, so I'm not that
impressed with the roofing industry's judgement to be honest. I do
agree, that overlapping layers so that gravity helps shed the water is a
good concept, but can't always be "adhered" to, especially on metal
roofs for instance.
However, I will also mention that while I am comfortable with L feet,
and think they do meet code; I am considering flashings on my next
asphalt roof project. I've made many changes to my practices over the
years, not always because I though it was necessary, but instead to
"keep up with the Solar Jones".
Have a good weekend,
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 8/6/2015 1:53 PM, William Miller wrote:
Daniel:
Good question, and worthy of revisiting.
As a contractor and businessman, I am obligated to reduce risk
exposure by using best evolved practices. This requires I used modern,
purpose-built, approved attachment hardware. To my knowledge, these
are all flashed.
No roofing contractor will honor a warranty on sealant-only
attachments. On pitched roofs, gravity is the main factor in shedding
rain water and flashed systems accomplish this.
Thanks for bringing this up.
William
On Aug 6, 2015, at 9:47 AM, Daniel Young <dyo...@dovetailsolar.com
<mailto:dyo...@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 Professional^TM : Cert #031508-90
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