Mounting L-feet to Corrugated metal roofing

zythros Registered Users Posts: 4
My roof is corrugated metal like the photo depiction here

I've looked at S5 but I've mostly been interested in Snap N racks simpler and cheaper innovations when it comes to mounting to metal roofing.

I thought about the corrugated footing they offered but realized that the sheet metal ridges do not always line up with the wooden support tgis running vertically up the roof at a 20 degree angle. So i thought about a mix of footings and these

Which go in the flat areas between the ridges and have a gasket to help protect against water. Eventually I realized that they aren't the same height with a 1/2 inch difference so I couldn't do that. Thinking this over I decided to just go with the flat attachments only and brace beneath the metal as needed to give me a good purchase and move away from the ridge..

However upon stumbling upon the first link I thought I had forgotten the proverb keep it simple stupid and was overthinking this whole thing all along I can buy the gasket depicted there individually  or just use a high quality caulking and screw my L-feet directly through the sheet metal and into the supports!.. The L-feet I have are the standard Uniracs and they are ridged at both angles.. which could be a problem with water build-up or abrasiveness to the metals paint.. So I'm thinking about using some kind of material equivalent to tar paper.. without the mess of tar paper.. cutting a rectangular piece aprx. an 8th thick laying it beneath the L-foot and having that serve as a cushion and a gasket to keep water out and then caulking the lag screw... sounds good? Or should I stick with the Unirac solutions.. I know a lot of people recommend S5 strongly but this sheet metal is 3/4 tall at the ridges and I'm pretty sure that if I was to jump onto the ridge It would flatten.. also I know they recommend using one at every ridge point and there $5 a piece.. it doesn't sound as secure to me and it costs more..

I've been a long time lurker and so far i've figured all this crapola out from reading from websites like these but im conflicted so I'm hoping you guys can give me that final push- as always


  • Anawa
    Anawa Solar Expert Posts: 225 ✭✭✭
    I've used both S5 and L brackets. 

    I like the S5 for ease of installation and overall stability. However, my S5 system (18 panels - configured 3x6) was put into place concurrently with the roof panel installation by the roofing contractor and was new construction. I traded with the contractor to: first, install 1x4 lathing boards over the entire roof (and aligned with the S5 clips locations); next, attach the roof panels; then, attach the S5 clips through the roof panel into the 1" lathing; and finally, lay and attach the panels to the S5's, connect the series panels together and then connect to the controller "home run" wire already laid under the ridge vent. This installation process was laid-out and explained to each roofing contractor that bid on the work. I share my experience if this option is available for you. My personal thoughts, S5 is great for new construction and trading with the roofer to install the clips, panels, and wire worked for me, but you've got to have it thought-out and all the parts and pieces available.

    For retrofits where the metal roof is aleady installed, L brackets will work. But, think through the entire installation process as you decide on the racking system for your situation, and then find the best price. I like to put a segment of peel-off mastic under the L bracket, but caulking is okay (but messy). I have attached additional 2x blocking along each side the rafters at the clip locations, I do this because I do not have a plywood substrate and it's easier to do than spend time "engineering" the exact locations of the joists from atop the roof, more times that not you'll be buggering the holes and making repairs to the rafters anyway.

    S5 will work on retrofits, but the installtion may be a bit more challenging. The clips must be attached to a suitable substrate. If you have at least a 1/2" plywood substrate, you are probably okay. 

    What kind of roofing system do you have, i.e. plywood deck, rafter spacing, rafter thickness, etc? Is this a retrofit? Are you self installing? How many panels? How high is the roof? Is the roof over living quarter or an "out" building?

    Good luck.

    in Georgia

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  • zythros
    zythros Registered Users Posts: 4
    edited December 2016 #3
    It's a barn shed the joist(tgis) are spaced 2 feet apart and on top of that is 1/2 OSB blue board followed by asphalt felt and then finally the metal roofing. The tgis are 3 inches wide by an 1 1/2 thick since I live in a somewhat milder climate I plan to space the L-feet by 4 feet as is the default recommendation for Uniracs design calculator for me , i'm using their standard rail.

    It took me awhile but i measured the center of the TGIs and then transferred that via sharpee to the roof.. I'm farily confident that I'm within a 1/4 of center for that one row... the TGI's have a slight bow to them as they go up. Considering how much time that took I may do one more batch higher up on the roof and then run a string line so I could estimate where the TGI's are.. If I find out I was wrong on my measurements then I'll be getting out the ladder and screwing runners between the TGI's.. hopefully I can avoid that the roof is 40x40 and 20 degrees which means a lot of ladder action.

    Theres a lot of different S5 clamps but I think your referring to this one instead of the one where it screws at an angle into the actual corrugation which I was thinking of earlier

    Ultimately my biggest issue with these is the height since my panel ridges are sporadically placed to the joist I'd have to use these in all the valleys as well which seems like a waste.Overall I have a large majority of flat areas with a TGI underneath them (like 18 flats to 2 ridges)

    I like the idea of peel off mastic yessir
  • zythros
    zythros Registered Users Posts: 4
    ..I think I've got it! I'll use 1/8 inch mastic tape below the L-feet in the valleys, and for the ridges I didn't think about it until now but I can use a corrugated footing of the right size because of the two holes here I'll just use the bottom hole for the corrugated footing and the top hole for the valleys should of thought of that one sooner.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,766 ✭✭✭✭✭✭
    If you think this part is crapola (your words) you are really not going to like it if you have to go up there to fix a leak or something else :)
    Are you sure that you can do a ground mount?
    "we go where power lines don't" Sierra Nevada mountain area

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    A couple of thoughts:
    1.  If I'm reading you correctly, your plan is to lag screw into the top chord of the tgi, hopefully within 1/4" of center?  I'd be a bit wary on that, as these are engineered products with specific requirements for cutting, drilling, and loading.  Wind loading on the panels could put the top chord of the joist in tension with the chord weakened by the bolt hole.  
    2.  You might also want to consider using butyl tape for sealing.  It's commonly used to seal deck fixtures on boats and RVs.  It doesn't dry out or shrink like some mastics and compresses well as you tighten bolts.  Best used in cooler weather (gets sticky when hot) for initial installation, and then torqued down when warmer.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,054 ✭✭✭✭✭
    Are you able to flat block with 3x's or 4x's between the TJI's. This would allow you to lag anywhere you please.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.