Drilling holes in the roof to mount solar panels

[Rb2]

Possibly I've missed something in all the replies, but having just installed 6 solar panels on my Rockwood Minilite, here is what I have to say. First be certain that 3/8 inch plywood is what you have. Generally with the structural panels that Rockwood and others use, this thickness is more like 3/16 inches. If that is the case, then it is important to figure out an appropriate attachment method that will hold in this type of material. Regardless of what you do, you certainly don't need 1 1/4 inch screws, only need to be long enough to accept your bracket and get through the plywood layer, however thick that is. What eventually worked for me, I used a 3/4 inch self tapping metal screw, not the type with the flared ends, and initially used these to secure the brackets, but even being very careful, I stripped a number of screws. So I went back, took out all the screws, and epoxied wooden golf tees into all the holes, (trick I learned working on alpine skis), once the epoxy set up, went back drilled a small pilot hole and again secured the brackets with the same screws. Worked very well, and the panels appear to be very secure.

I made my own brackets, because I wanted to have a larger bracket holding more screws, so less stress on each screw, and as I recall, the cost was less than if I had bought brackets. I bought z shaped aluminum in as I 3 foot lengths or maybe 4, then cut these down to use.

But in summary, make sure how much plywood you have to screw into and go from there. Also, attaching to the rubber roof with tape, is trusting that your rubber roof membrane is not going to separate from the substrate under it, I personally would not want to gamble on that one.

Good luck, I love my solar system.

[Tahoerockwood]

I installed two PV panel two yrs ago and the sys works great , 2 great 6 volt batts, runs ice maker or micro wave and everything else with 2000 watt inverter.


I don't believe you have a 3/8" roof, most are a sandwich of 1/4"ply, foam and 1/8' ceiling material. I used a 5/8" x 1 1/2 build up strip the width of the roof covered over and sealed with the membrane you mentioned. I then thru bolted the panel clips with a 1/4" x 2 x1/2 SS bolt and used a Chrome fishing washer in ceiling area. I don't think you will find any wiring in the middle area and the slide works fine.


We have a Rockwood 8296SS behind a Banks fed 96 F-250 that goes down the road 70MPH. I wanted air under panels and didn't want them blowing off roof.
Have fun.

[larry2c]

I pulled our bathroom vent trim piece out and looked before I started drilling - it is 3/8 thick but maybe it's OSD and not plywood. I bought screws that are made for mounting tin roofs - these have a built in rubber and metal washer. They are not self taping but they have a deeper thread than the standard self tapping screws. I drilled a .110" pilot hole and actually hit a "stud" on two of the 4 brackets for each panel.

Between the screws, the butyl material under the brackets, the Dicor on top of the brackets and the Eternabond tape I'll be putting on once the Dicor cures, I think the panels are going to be fine.

[babock]

I keep on forgetting you don't have a rubber roof..just removed my post about that.

[Prunyon]

Before you put Dicor on your roof you may want to check to see if you have Alfa roof fabric cause it could void your roof warranty.

[larry2c]

Originally Posted by Prunyon

Before you put Dicor on your roof you may want to check to see if you have Alfa roof fabric cause it could void your roof warranty.

It's TPO but thanks for the warning

[babock]

Originally Posted by larry2c

It's TPO but thanks for the warning

So you do have a rubber roof. Just so you know, the bond between your roof and the plywood is pretty poor so the only thing really holding down the panels are the screws so make sure you have enough of them. The Dicor, the Eternabond and the butyl are basically doing nothing for holding the panels down.

Each on my hold down brackets has 3 or 4 screws and 1 of them is in a stud for the most part.

Since some Rockwoods have aluminum framing in the roof, you want to screw into one of those at least for the leading edge if you have them.

[larry2c]

Thanks Babock - I didn't realize a TPO roof was considered a rubber roof.

I understand that the TPO material is not bonded to the plywood roof in a significant way and I'm not trying to infer that the Dicor & Eternabond are capable of holding down the PV panels on their own. As I mentioned, I bought screws that I believe will have significantly improved engagement over the ones that came with the kit. There are two screws in each "foot" of the mounts and currently there are 4 mounts per panel.

For the record, I once again reached out to FR's service folks in the hopes of getting a drawing showing where the ceiling joist are. After several tries and no response I moved on.

I will be keeping an eye on the panels/mounts over time to see of there is any sign of them coming loose as we travel. Maybe I'll invest in a newer stud finder that has the "deep" option as one post mentioned and go hunting for the cross frame members again.