[RE-wrenches] Flashing vs Sealant... again (is sealant code defensible?)

[Troy Harvey]

Ray, Your logic is similar to mine. Around here, there are lots of corten and galvanized corrugated roofs that are attached with screws with rubber washers. L-feet are definitely way-better sealed than that.

I looked up the IRC, The Flashing section R903.2 is pretty vague., could be interpreted any way you want. However R903.1 General does say to follow the roofing manufacturers instructions.







On Apr 14, 2014, at 3:20 PM, Ray Walters <ray at solarray.com> wrote:

>  Hi Glenn;
> 
> How do you and the roofers deal with Propanel steel roofs? That's hundreds of penetrations for the screws, with no flashings, and they depend on just a little rubber gasket.  Or how about the lead head nails on a corrugated metal roof?  Roofers themselves make plenty of unflashed penetrations by your definition. Instead, I would call those roofing attachments, not penetrations.
>      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.  Bulkheads on water tanks and boats use the same method, and hold not just against moisture intrusion, but moisture under pressure.  How many PSI can a flashing take? 
>     With L feet, we're doing less damage to the roof underneath: one .05 sq in. hole through the roof, then covered by 80 times its surface area with 1/4" aluminum over a roofing approved sealant held mechanically under pressure.  With flashings, you are tearing up the original roof, separating shingles from each other, ripping out mounting nails, tearing the undersides of the shingles, and removing many square inches of shingle off the roof, all to install a  200 sq in flashing to cover a 0.05 sq in hole. I've done it both ways, and I think you've got more of a chance of causing a leak installing flashings, especially on an older roof.  Flashings make more sense on new construction, when the roofer can install the roof over the flashings after.
>     The L foot mounting method was developed in the hot water days, and predates PV by over a decade.  We've got more proven long term success with this mounting method than most module companies today can claim for their products  (or makers of the latest flashings for that matter).  Instead of all this knee jerk: flashing = good, L feet = bad,  how about the roofing and solar industries coming up with actual testing to determine what mounting methods actually leak, and which ones don't?  Meanwhile, many on the list have already pointed out: L feet installed with the correct sealant have lasted as long as the comp roofs they're on, 30 + years.    
>     Don't get me wrong, I use conventional flashings in many situations, especially on flat roofs.  The Chemlink flashing is a favorite, but yes, it depends on chemicals to provide the moisture barrier, as do most roofing materials ( including comp roofs and most commercial flat roofs).  
> <chemlink_1_part_pourable_sealer.jpg> Chemlink Flashing utilizes a 2 part adhesive process.
> 
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer, 
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> On 4/13/2014 7:22 PM, Glenn Burt wrote:
>> In New York solar installations are required to have all penetrations flashed – chemical sealant is not flashing. Ask any roofer what he thinks about drilling through the roof and relying on purely a chemical adhesive/sealant for the prevention of water intrusion, and he will laugh at you.
>>  
>> Glenn Burt
>> One of many inspectors for the NYSERDA PV and Thermal incentive programs…
>>  
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