Hi John
When you say ' corrugated ---with flat spans and ribs-- do you mean what is
generally called Grand Rib around here in Va. 8" flat panel with a low 1" wide
area in the middle of the flat panel, then a rib 1"+ high, held on to the roof
sheathing with hex head screws and sealing washers?
If so, we just did a job like that and used ' Peel and Stick ' membrane cut to
make pads under the L feet, predrilled for the 5/16" x 3" lags into as many
truss top chords or rafters we could hit--the ribs sometimes intervene, in
which case we use 3/8 2" lags-- with a healthy dollup of black silicone in the
hole and under the L feet. When the silicone squeezes out from under the foot,
I always smooth it out with a finger, especially on the uphill side to better
shed water and avoid an area where freeze- thaw can degrade the bond to the
roof. Be sure the metal in clean before application. The silicone should
squeeze out of the hole as the lag goes in, and any silicone on your finger is
applied to the head of the lag, but that is more a place to get rid of it than
a permanent water barrier.
If it's true sinusoidal corrogated about 5 years ago we mounted a thermal panel
by making custom feet that spanned two peaks with a EPDM rubber gasket under
the foot where the screws penetrated, one into each peak. Hard to hit rafters,
so decking type , thickness, decking fasterner type and schedule, metal
thickness, and L foot screw diameter are all important factors, dependent on
your wind and snow loads.
How will you handle the expansion /contraction issue ?
I've used this general method for 30 years, starting with thermal panels.
There will probably be other suggestions as well. More than one way, so long as
compounds are compatible.
Ken @ CommonWealth Solar
----- Original Message -----
From: cvso...@aol.com
To: re-wrenches@lists.re-wrenches.org
Sent: Friday, November 26, 2010 8:55 AM
Subject: [RE-wrenches] Mounting L feet on corrugated metal roof.
Wrenches,
Do you have any tips, stories, methods for mounting L feet on the
corrugated metal roof that has short flat spans and ribs.
After all these years, I am facing my first install on this kind of roof. We
originally were going to install 6 top of pole mounts but he decided the
neighbors would not like the appearance so now we are looking at a 20 x 40'
metal roof on the garage. The customer asked about flashing the L feet. I'm
at a loss to figure out how to do that.
John Blittersdorf
Central Vermont Solar & Wind
Rutland, VT 05701
cvso...@aol.com
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