Hybrid Car – More Fun with Less Gas

Proper Flashing of Mounts on Comp Shingle Roof

register ::  Login Password  :: Lost Password?
Posted by Jerry Krinock on August 8, 2003, 5:07 pm
 
Hi,

I've been able to learn most of what I need to install my PV system by
buying codes, searching the internet and reading books.  But the
knowledge of roofing seems to be handed down only through experience.

I have purchased 32 STR-6 standoffs made by Unirac.  (I'm not using
their rails since I want something stronger than sliding bolts in a
track to hold my large Sharp panels).  Anyhow, these things consist of
about a 1-inch pipe which points out from the roof, welded to a flat
square flange on the bottom, about  3x3 inches.  The flange is
supposed to lay on the roof "under the shingles", and is fastened with
3/8 inch lag screws that are supposed to go through the plywood and
into the roof joists.  The flange is supposed to be covered by a
flashing assembly of the type available at Home Depot etc. for
plumbing vent pipes.

So, it seems simple, but I have several questions and would appreciate
any advice from anyone who knows composition asphalt shingle roofs.

1.  This 4/12 slope roof is 12 years old, made of "20 year" shingles,
and shows no signs of wear or missing granules.   The PV panels will
sit about 8 inches off the roof, and will cover the entire roof on
both sides, right down to the gutters, effectively shading it from
sun, wind, rain and hail from now on.  Therefore, this roof is going
to last forever,  and I need not consider reroofing before installing
the modules.  True?

2.  It is possible to properly install these standoffs (spaced about
every 4 feet) without re-roofing??   That is, by carefully locating
the roof joists, cutting out a square of singles down to the black
underlayment big enough for the flange, drilling holes and screwing in
the lag screws, then lifting up the shingles "uphill" from the
standoff and sliding the flashing under them.  Will this work?

3.  The flashing itself should be fastened with a couple galvanized
nails or screws, also under the shingles on the "uphill" side.

4.  Any advice on how to avoid breaking the uphill shingles while
working under them??  Probably working on a hot day would be best,
since the shingles will be more pliable.

5.  I've noticed that the bottoms of new shingles seem to have an
adhesive on their "downhill" side, probably to keep the wind from
blowing them up.  Should I reapply some kind of adhesive to make them
stick to the new flashings I've installed?

THANKS for any advice!

Jerry Krinock
in San Jose, CA  USA

Posted by Joe Fischer on August 9, 2003, 12:58 am
 
:
: I've been able to learn most of what I need to install my PV system by
: buying codes, searching the internet and reading books.  But the
: knowledge of roofing seems to be handed down only through experience.

      And that may not even be enough.
 
: I have purchased 32 STR-6 standoffs made by Unirac.  (I'm not using
: their rails since I want something stronger than sliding bolts in a
: track to hold my large Sharp panels).  Anyhow, these things consist of
: about a 1-inch pipe which points out from the roof, welded to a flat
: square flange on the bottom, about  3x3 inches.  The flange is
: supposed to lay on the roof "under the shingles", and is fastened with
: 3/8 inch lag screws that are supposed to go through the plywood and
: into the roof joists.  The flange is supposed to be covered by a
: flashing assembly of the type available at Home Depot etc. for
: plumbing vent pipes.

      All flashing has to be done so that it will
be waterproof without adhesive of any kind.
      And working on 10 year-old shingles will almost
certainly cause leaks.
    
      It would be good to find some installations and
look at them, and ask experienced installers these
same questions.

      The vent flashing has to be under the shingle
above, and over the one below, so that water will
just by gravity never flow under a shingle.  

      Have you found how much above the roof panels
are usually installed, if you cover the whole roof,
won't it be  problem to repair any leaks?

      Surely there are homes in the area where you
can talk to the owner and maybe even examine the
installation.

      I would want flashing to fit tight over the
one inch pipe and be at least 10 or 12 inches square,
so the top will go way up under the above shingle
and also be wide enough to keep water from flowing
toward the flange.
      The thickness of the flange might hold the
flashing up so that water can blow under it, so
check into the shape and what it is made of,
I am not sure if any is normally made to work
on a one inch pipe, it may need to be a special
item only available to solar panel or sign
installers.

      I am not sure I would want to do the
install, are there any solar panel installers
with insurance certificates to protect you?
  
      It seems like the thing to do would be
to mount all the flanges and flash them, and
spray water at all angles to test for leaks
before installing any panels.
      And it might be best to install panels
with space betwen them for working on them,
or removing any one panel to do repair work
on the roof without having to remove them all.

_IMPORTANT_

      If it was me, I am inclined to think
that if I was going to do the install myself,
I would build a test roof about 8 feet by 8 feet
and cover it with shingles, and install a panel
there, and spray water and be  able to check
for leaks real easy.

      Thick adhesive can be applied under and
over the flanges, but it should not be relied
on, all flashing must be waterproof with just
gravity flow.

Joe Fischer

--
3

Posted by Jerry Krinock on August 9, 2003, 3:25 am
 in article 3f34474a_1@news.iglou.com, Joe Fischer at
gravity1@shell1.iglou.com wrote on 03/08/08 17:58:


OK.  That's what I thought.


Because they will crack, I guess??


I'm thinking maybe I should get a roofing contractor up there, but I can
almost guarantee that he'll recommend replacing the whole roof, "because
when you've got a hammer...everything looks like a nail".


Well, as I said I'm installing my panels 8 inches above the roof, for
various reasons.  The way I have designed the racks, it should be fairly
remove panels and lay them on top of their neighbors for maintenance.


Yeah...I guess the raised part of the flashing must be bigger than the
flange.


That may be a good idea, to do a test.  I just realized, that if it doesn't
work, I can always have a roofing contractor to remove the whole roof,
install the standoffs with flashing, and then re-roof.  All I've have lost
is my time up there.


Got it.

Thanks, Joe.


Posted by Eric on August 9, 2003, 8:20 pm
 
What you all are saying about flashing is technically correct, but
many, many solar arrays are mounted with feet caulked (with high
quality urethane) and lagged right through the shingles, into a rafter
or blocking.  This is why the flange is often square - so it can be
put on in a diamond orientation, helping to divert water.
If you want to use the nice flashings, which should give a better job,
they can be worked into the existing shingles by a roofer, I believe.

Eric



Posted by Joe Fischer on August 9, 2003, 9:16 pm
 : What you all are saying about flashing is technically correct, but
: many, many solar arrays are mounted with feet caulked (with high
: quality urethane) and lagged right through the shingles, into a rafter
: or blocking.  This is why the flange is often square - so it can be
: put on in a diamond orientation, helping to divert water.
: If you want to use the nice flashings, which should give a better job,
: they can be worked into the existing shingles by a roofer, I believe.

       There is a lot of use of adhesives in regular
roofing now, but it is not the recommended way, mostly
because structures flex in wind and time, breaking loose
any adhesive, especially as it becomes more brittle
due to drying and weathering.

       Cutting costs and reducing prices may be even
prompting trade roofers to use more adhesives, but
it should be avoided if possible on your own building.

       If he already has the standoff flanges he
should try to get the custom flashing for those,
and get two sheets of plywood and build a test
roof near the ground to experiment if he is
going to do the work himself, or even to get
enough knowledge to heckle contractors. :-)

Joe Fischer

--
3

This Thread
Bookmark this thread:
 
 
 
 
 
 
  •  
  • Subject
  • Author
  • Date
please rate this thread