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

[Glenn Burt]

In New York solar installations are required to have all penetrations
flashed - chemical sealant is not flashing. An asphalt rooftop that sees
temperature swings from -20 to 130F are a concern for simple thermal
movement and I lost count of how many L feet I have seen with half a tube of
silicone or worse yet Sikaflex goobered all around them. 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.

NYS Building code 1503.2 is the primary reference for requiring flashing for
all roof penetrations.

The NYS 2010 residential code M2301.2.7, R903.2 all refer to 'flashing' and
sealing.

The National Roofing Contractors Association provides guidance for asphalt
shingles and penetrations.

Checking with many roofing manufacturers also has shown that they require
flashing penetrations to maintain their warranties - not using flashing is a
violation of the roofing installation instructions.

 

Yes it is more expensive - but it is like insurance, you don't need it until
you need it, but then there is no substitute for it. Of course if you are
big enough with deep enough pockets you can take more chances with roof
penetrations, and maybe you will not run into a call-back for a leaking
roof. But if you do, wouldn't you have a stronger position with the customer
by saying all penetrations were flashed in accordance with standard roofing
contractors and manufacturer's specifications instead of 'well I shot
everything full of sealant and it is what I have been doing for
years/hundreds of holes in roofs'.

 

I can't see in this day and age any reason not to use one of the many
commercially available flashing solutions. Now 5 years ago, was a different
time, and we formed our own flashing out of Al coil stock because there was
no good solution available at that time.

 

Hope this helps in your decisions.

 

Glenn Burt

One of many inspectors for the NYSERDA PV and Thermal incentive programs.

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Troy Harvey
Sent: Friday, April 11, 2014 3:20 PM
To: RE-wrenches
Subject: [RE-wrenches] Flashing vs Sealant... again (is sealant code
defensible?)

 

1. I'm interest in a poll of installers who are using flashings vs sealant.
Now that the flashing market has evolved, what are you using today? When did
you switch to flashings (if you did). And why not, if you still prefer
sealant.

 

2. Is there a any code defense for sealant systems ? (L-foot sealed down to
shingles). Does anyone know of a scientific shootout between sealants and
flashings?

 

Here is my view: The construction industry is slow to evolve. Sealants,
clauks & adhesives are not trusted in general, due to the legacy of code,
and we have a mechanical vs. chemical industry bias. 

 

There is something about seeing a flashing that says, that is a
"professional job", it must comply with code. And yet, my experience says
I'd trust a 50-year silicone over a flashing that depends on gravity.
Gravity should be dependable right? But anyone in snow country can tell you
in spring, water can go uphill after ice dams form. There are high-rise
buildings that use "structural glazing" which is just glass and silicone.
These systems are now getting to be 50 years old without issue.

 

The cost of flashings have come down in the last few years, but so has the
cost per watt of installs. With 50 feet in a typical install around here
that is $150 in feet, lags & silicone. Or $1500 in flashings, and extra
labor. That can be a large part of a bid, and make you more expensive in a
competitive landscape. That is fine, if it adds value... but I personally
don't see the proven value, other than the "appearance" of code
defensibility. Anybody have proof?

 

thanks,

Troy Harvey
---------------------
Principal Engineer
Heliocentric
801-453-9434
taharvey at heliocentric.org

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