[RE-wrenches] Stanchions for Comp Shingle Roofs

[Bill Brooks]

Glenn and Peter,

 

I just reviewed a few of the Technical Data sheets for Sikaflex and they do
caution its use with asphalt shingles. They make the statement that these
products should not be used in the presence of a product that might “bleed
oil.” Of course the asphalt in shingles can bleed oil, but it will have this
affect on all sealants other than tar. 

 

Tar does not have good adhesion to many materials, including aluminum, so I
believe Sika is simply covering their buttocks. Alternatively, DAP has a
nearly identical product that does recommend use on asphalt shingles. It is
not substantially different and would still have the issues of “bleeding
oil”. However, history tells us that these polyurethane caulks are
exceptional in their durability on comp shingle roofs, so use the DAP
product if you think the caulk manufacturer needs to backup the application.

 

Bill.

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Glenn Burt
Sent: Monday, September 15, 2008 10:02 AM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Stanchions for Comp Shingle Roofs

 

Quick item on Approach #1 bares repeating – Sika is incompatible with
asphalt shingle roofing according to the manufacturer


 

 

Regards,

 

Glenn Burt

Technical Specialist

Renewable Power Systems, LLC

PO Box 967

Averill Park, NY 12018

V: 518-674-5808

C: 518-810-3174

F: 518-514-1175

E: gburt at RPSPower.com

www.RPSpower.com

 

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Peter
Parrish
Sent: Monday, September 15, 2008 12:28 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Stanchions for Comp Shingle Roofs

 

I’m not sure if we have discussed this before, but I would like to get
opinions on the relative merits of the following two approaches to setting
stanchions and flashing them in for a roof mounted PV system:

 

Existing comp shingle roof in good condition. Professional Solar Fast-Jacks
(or similar stanchions that result in a ¾” to 1” post to which to attach
rails). I am not endorsing ProSolar products, I just wanted a specific
example to work with.

 

Approach #1: Lag stanchions directly onto existing comp shingle roof; cut a
inverted “U” into the top layer of shingle; slip in Oatey-style flashing
(9”x12”, with an elastomeric ring); seal exposed vertical edges of flashing
with a bead of high quality caulk (Sika 1A)

 

Approach #2: Remove shingles down to the felt; lag stanchion; replace
shingles incorporating full-sized (15”x18”) flashing and seal top of
flashing with high-quality caulk.

 

Obviously, approach #2 takes longer and costs more, but does it confer
commensurate benefit? If the resulting stanchion/flashing were exposed to
the elements, I would tend to favor the latter approach; and if we were
dealing with new construction the difference in time and money would not be
significant. However, if the stanchion/flashing lies directly underneath a
PV module, it will be shaded from the deleterious effects of UV sunlight and
will not receive any direct rain or snow accumulation. Under these specific
circumstances, I would argue that approach #1 should be more than adequate
and last at least as long as an existing comp shingle roof. 

 

For those of you who haven’t seen the Fast-Jack/Oatey approach, you might
want to look at http://www.prosolar.com/Oateys.htm.  

 

 - Peter

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com 

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