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-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@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: 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 ________________________________ _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ________________________________ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.872 / Virus Database: 271.1.1/3281 - Release Date: 11/26/10 02:34:00
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