[RE-wrenches] Mounting L feet on corrugated metal roof.

Fri Nov 26 07:48:43 PST 2010

It sounds more like "Grand Rib" rather than sinusoidal. What we normally
do is mount the L-Feet directly to the flat metal sections with a
healthy amount of sealant, similarly creating a watershed on the uphill
side. In my experience, the pad is not necessary. We never crush the rib
with an L-Foot. Although it is time consuming, getting in the attic and
adding blocking between the rafters is preferred. Adjusting L-Feet side
to side without exceeding maximum spans it the way to go in my opinion.
It really depends on the roof structure. If every L Foot is going to
require blocking due to the spacing of the ribs, it could be quite a
job.

One more thing... I have been looking at a product from Eco-Fasten
called Simple Seal that might be helpful. I have no experience with it
yet - any wrenches used it?

Jason Szumlanski

Fafco Solar

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ken
Schaal
Sent: Friday, November 26, 2010 9:34 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Mounting L feet on corrugated metal roof.

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: cvsolar at aol.com 

	To: re-wrenches at 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

	cvsolar at aol.com

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