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Thursday, November 6, 2014

Sagging RV Roof Relief

Doc, I have read your solution on repairing sagging roofs with plywood. You mention in your answer that you can put this spacer between the metal roof and the roof rafters. Can you do this same procedure for rubber roofed RVs? Thanks, Larry B.

Larry, that earlier solution you read pertained only to hollow roof systems with aluminum sheathing simply installed over roof rafters; what we call “stick” construction. Though there may still be a few out there, the vast majority of RVs today have a vacuum-bonded, solid roofing structure. Basically it’s a one-piece roof consisting of plywood decking on top, some type of insulation installed between the support rafters (wood, aluminum or steel), with a panel type of ceiling finish. The whole structure is built on a flat, vacuum table, glued together and set on top of the walls. The synthetic membrane (sometimes fiberglass or aluminum) is then installed once the roof is secured to the side walls.

So the sagging roof solution in that earlier Q&A does not apply to one-piece, synthetic roofs like EPDM, TPO or fiberglass, unfortunately. The solution for a sold roof that sags is to first determine and rectify why it sags, then remove the rubber membrane and either replace the top decking with thicker plywood (preferred), or simply install another layer of plywood over the existing plywood decking. Of course, this assumes all the rafters and support members are not damaged and remain intact. But rather than installing rubber membrane again, I recommend a newer type of roofing system called RV Armor. Take a look at this web page and watch this video about the RV Armor system. It is actually preferred to install the RV Armor system on plain wood decking rather than over the final finish material when possible, so you have a golden opportunity now if you replace the decking. As I often state, serious RVers should definitely investigate its benefits!


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