What type of roof does our Motorhome have? and What type of fasteners are the best to secure Solar Panel brackets or strut channels to it?


New Member
Jan 22, 2021
North Vancouver, Canada
Hi all,

We have a class C 1986 Ford E-350 (Vanguard 1985) motorhome. We were wondering about the best fastener solution for strut channels and/or solar panel brackets to the roof. We are planning to install the panels on the front (the cab roof).

Would we just screw them to the roof (and what type of screw) and then seal them? Should we use rivet nuts with lag bolts?

For any solution that we would come up with, we would make sure to seal and also use double-sided tape (VHB).

How can we find out what material the roof is made of?

Here is the photo of the roof:
It looks like a rubber roof, but most EPDM roofs are white, not black. An EPDM roof that is black has lost it's top coating I think. VHB tape is not appropriate on a rubber roof.

Here is my install write-up for my rubber roof:

It looks like the rubber roof used on the flat roofs of houses. I have not seen that on a RV before.
Thank you @HRTKD for including a link to your write-up. It's a really great resource.

@Q-Dog, we also were completing about that idea and probably going to end up removing a vent when the weather is nicer.

When we step on the front side of the roof, it kind of feels like we are walking on a sheet metal (the way it flexes or sounds) covered by other materials.
Howcome I can't see the picture?
1985 Vanguard will probably have an aluminium roof, quite often they had no underlay other than the fibreglass batt insulation and then the interior ceiling panel. People tried all kinds of remedies if they suspected a leak, including roofing tar. You would have to find a wood support to attach to-quite often they were 2x2 lumber. Are there aluminium nails holding the ceiling panels up?
I'm in Steveston.....
For your other post are you stuck on 100w panels? This is from Amray solar in Lake City...
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Hi @Whinny , thanks.

Yes, the roof seems to have a coat of black substance (could be silicon paint). The stud finder would be useful to find those 2x2 lumbers under the aluminum. We haven't noticed any visible aluminum nails. The previous owner has taken the AC unit/vent out and has covered it with we think EternaBond tape and painted over the tape. So we have to be careful when we walk around that area of the roof which is in the back part. We have taken some of the inner wall panels off inside the RV and it looks like the studs/lumbers on the back wall are glued and stapled together.

Let's say the motorhome has an aluminum roof with 2x2 lumber support underneath. What are the best solutions to mount/fix the panels (or strut channels) to the roof?

Oh wow, that's a great deal on CL. Very tempting. We have already purchased four 100W Renogy panels.

Here is the picture again:

If that's really an aluminum roof and you're not finding any fasteners, you may be in the same situation as someone with a rubber roof. Using just tape to secure the panels to the roof could result in lifting the aluminum skin off the subsurface.
I'm quite sure that is not original, it may be a torch on membrane over plywood. At any rate there will be framing you can screw into with a "Z" type bracket. I prefer homemade brackets using 2 pieces of angle aluminium bolted together. Bed them in butyl tape and use lap sealant all around.
using a ladder rack for vans is a good way to go but you may have to extend the width of the cross bar and the brackets will no doubt be right where the framing is to screw into , using a good sealant plus it will lift your solar panels up off the roof for cooling ,you also notice extra cooling in the rv being shaded by the panels themselves
Thank you all. We are getting back to this project again. We have been trying to find the thick wood support under the roof surface with a stud finder. It's kind of hard since the roof has some surface bumps (it's not locally super flat). Based on our markings on the roof, there are trusses every 18" - 20". But when we try to find them from inside the RV (where there are visible painted nails), the trusses are spaced out every 16".

The aluminum roof at some spots has a bit of play, so we can verify the lines for trusses with hand.

We decided to use unistrut channels with Renogy Adjustable Solar Panel Tilt Mount Brackets attached. Panels will be flat when we are on the road but can be tilted when we are parked and it's no super windy.

Also planning to use #10 sheet metal screws (1-1/2" deep) along with fender washers to fasten the struts to the roof (probably 9 screws per strut channel). For this we have read that it is good to predrill the roof first, then pour in some lap sealant in the hole then screw in the strut to the roof (possibly use lap sealant and/or butyl tape between the roof and the strut). And finally, cover the screw head with a generous amount of lap sleant.

Adjustable Solar Panel Tilt Mount will be fastened to the strut channels using strut spring nuts (3/8" ID), 3/8" bolt (1" long), and possibly strut square washers (3/8" ID).