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Concrete tile root without underlayment, how to install solar panels

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  • Concrete tile root without underlayment, how to install solar panels

    My roof is using concrete tiles, but no plywood and underlayment, in short no sheeting, tiles are stacked on trusses. See picture.
    Several companies expressed they can not do it and suggested me to re-roof with plywood.
    One company mentioned they can install with S hook, I am in Northern California.
    Anybody has the same type of roof structure and was able to install solar panels without re-roofing like adding plywood ?

    image0.jpeg
    Last edited by scurffy; 01-10-2022, 04:56 AM.

  • #2
    IMHO, a tile roof like that is a huge leak risk, and I as an installer would not go near it. I think tile is really just weather protection for the underlayment which is the actual water proof barrier. Seriously - there is so much substandard construction that went on in past decades. Those trusses even look weak.
    As Ken Mattingly said in the movie Apollo 13 when practicing in the simulator - "Let's get it right"
    BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

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    • #3
      How old is the dwelling ?

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      • #4
        You never had a leak? Hard to imagine putting solar panels on that roof without causing a leak.

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        • #5
          The house is about 41 years old, so far no leak

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          • #6
            Originally posted by scurffy View Post
            The house is about 41 years old, so far no leak
            One reason for the no leaks might be you haven't drilled a lot of holes in the roof. Expect a bunch of holes with a new array.

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            • #7
              I was told some installers use S hook, which did not drill holes on tiles, more the wood structure below it, just I am not clear how it was done, there are beams and wood panels, the S hook is on beams or wood panels ?

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              • #8
                Tile-hooks will probably not work because the hooks depend on the battens being in the right place.
                In fact, there is little you can do on this roof that is code compliant. Code requires solar mounts being fastened to the roof framing and the roof framing shown is only 3/4" thick and will not hold anything bigger than a deck screw. Solar roof fasteners are all at least 1/4" or 5/6" thick. Any structural engineer (many AHJ's now require a PE stamp on all solar roof mounts) is going to tell you to rebuild the entire roof in order to add solar to it.
                BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

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                • #9
                  So I need to get a roofer to install pywood on top of it. Assuming I did that, will I still have the issue that solar panels need to be on roof framing but only 3/4" thick. I am pretty sure If I add plywood on top, it will not going to change the roof framing, the rafters size will still the same. I am not sure plywood will be strong to hold solar panels in high wind condition. Any thoughts ?

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                  • #10
                    Originally posted by scurffy View Post
                    So I need to get a roofer to install pywood on top of it. Assuming I did that, will I still have the issue that solar panels need to be on roof framing but only 3/4" thick. I am pretty sure If I add plywood on top, it will not going to change the roof framing, the rafters size will still the same. I am not sure plywood will be strong to hold solar panels in high wind condition. Any thoughts ?
                    Yea, take the application to a P.E, who claims professional competence in structural engineering and design of structures for wind loadings.

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                    • #11
                      Originally posted by scurffy View Post
                      So I need to get a roofer to install pywood on top of it. Assuming I did that, will I still have the issue that solar panels need to be on roof framing but only 3/4" thick. I am pretty sure If I add plywood on top, it will not going to change the roof framing, the rafters size will still the same. I am not sure plywood will be strong to hold solar panels in high wind condition. Any thoughts ?
                      Trusses and rafters are generally considered the structural framing. Plywood seating can add strength but the thickness is not enough for the uplift loads. An engineer is needed as suggested by earlier posts.
                      9 kW solar. Driving EVs since 2012

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                      • #12
                        After asking several people, it seems the reason for solar companies stay away from my roof is for the potential leaks in the future, more on disturbing existing roof, and later to fix it will drag their resources. The possibility for leaks is high after installing solar panels, even I don't have leaks now. From installing panels point of view, even with plywood, the installer need to ping point the location of rafters, not just anywhere on plywood. So from structure engineering point, with or without plywood make no difference, because it needs to mount on rafters. As for uplift loads, we don't have hurricane here, even with strong wind, it won't even move the tiles. (cement tile is heavy). I do have one company can do it, the question is more can they support it later. So the final decision is more on potential leaks. Of course this will double my solar installation. ROI is out of question, more on go green helping the earth.

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