[RE-wrenches] Flashing vs Sealant... again

[William Korthof]

Over the years (13 so far) I've installed probably 50-100 systems non-flashed on comp shingle, and about ten times that number flashed. The early ones were mostly non-flashed, the later ones nearly all flashed. The switch was around 2005, as I recall. The presence or lack of flashing has had little or nothing to do with the risk of a leak, in my experience. I would readily service every one of our customers in the event of a workmanship issue. 
We migrated to flashings for a number of reasons, but I can't say that leak-prevention was one of them. Perception of quality, conventions in the roofing trade, and perception of serviceability were factors. The cost penalty of going to flashings was manageable and justified for us at the time because margins were comfortable and increasing, and it seemed like more durable workmanship (our warranties also increased from 5 to 10 years). I could see revisiting the practice---cost needs to be a consideration if we want to continue seeing PV proliferation. 

In terms of preserving roof integrity and preventing leaks, unsealed/missed pilot holes, faulty roof construction, and faulty products (attempting to use Henry's wet patch as a permanent seal) seem like the real factors, not flashings. On flat roofs, issues with drains clogging and ponding are the issues I've seen.

Although I would count among the installers to use flashing, I accept the arguments from the proponents of no-flashing installation. 

/wk

William Korthof
714.875.3576
Sustainable Solutions
#956904

On Apr 16, 2014, at 8:52 AM, <don at energysolarnow.com> wrote:

As Ray Walters wrote, L feet installed with the correct sealant have lasted as long as the comp roofs they're 
on. 
As can be seen in the attached pictures of L-feet on a roof that I will soon be repairing, the wrong sealant eventually shrinks and separates from the L-foot. Also the slotted hole where the lag penetrates is exposed.  That's why flashings are used-- to cover up sealant that won't last.
Thanks for all the pointers to better sealants.

Don Barch
Energy Solar

Ray Walters <ray at solarray.com> wrote:
....If I'm putting a 2 inch hole through a roof, then that constitutes 
a penetration, and using a flashing is usually a good idea. But when 
I'm filling a 1/4" hole with a 5/16" lag, its really much closer to 
being a roofing attachment than a penetration.
BTW, we're not just depending on some adhesive to stop the 
moisture. An L foot is really a 1/4" thick aluminum flashing. It has 
at least 4 sq in. of surface area held permanently in place by a 
mechanical fastener that is applying a significant amount of downward 
pressure.
 ..... L feet installed 
with the correct sealant have lasted as long as the comp roofs they're 
on, 30 + years.
<Mount_foot6.JPG>
<Mount_foot11.JPG>
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