Originally Posted by Melweiler
How thick is the plywood that you used on your roof?
This post may help on new roof board thickness. I went into different thickness option details there. https://www.sunlineclub.com/forums/f...tch-19201.html
How thick the plywood needs to be sort of depends on the size of the roof repair you are doing.
A total reroof, I have used 2 choices,
Non - walk on roof, Nominal 1/4" which measures close to a heavy 3/16". It measured 0.217" or 5.5mm. This thinner material allow the EPDM/TPO or PVC membrane to be glued to the plywood, sheds water well, avoids ponding water areas sunken down and saves weight on campers that do not want to give up cargo carrying for added roof weight. You still need to use small plywood sheets to walk over this.
Walk on roof, Nominal 3/8" which is more close 11/32" thick. This is thick enough to walk on directly and no extra plywood servicing sheets like the thinner plywood. This has some loss of cargo capacity using this, but it is not much pending the size of the camper and what is more important, a full walk on roof or loss of a small amount of cargo capacity.
At least one club member used 7/16" thick OSB. This will work but it does create issues if you are trying to reuse the old moldings. There are work arounds, and this can be used, but it would not be my first choice. It weighs more, and uses up more cargo capacity on the camper. Costs more, but it will work.
When using plywood, I look for BCX plywood, meaning B sanded side up to membrane, C side down and X for exterior glue. Whatever you do, do not get CDX like on a standard house roof with shingles. The C side is pretty course and can have a knot hole exposed in a layer. It is not a problem for an asphalt shingles but can be when gluing a flexible membrane down to it.
If you are doing a small roof "patch" like a water damaged corner that has 2 ft x 2 ft water damaged corrugate budboard, then you can use 1/8" luan plywood with supports under it in that area. It will allow you to glue the membrane down, not create side molding issues with the thin layer and shed water. You cannot walk on this with out support plywood on top. I myself would not use 1/8" plywood on the entire roof, it's to thin and I can see ponding issues between rafters over time due to just not enough stiffness.
Hope this helps.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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