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Old 09-01-2017, 02:47 PM   #1
2 Rivet Member
1969 31' Sovereign
Satellite Beach , Florida
Join Date: Jul 2017
Posts: 22
Waterproofing subfloor

Question I would like to have considered is this, would it be feasible to achieve a long lasting, watertight seal by doing the following: First, utilizing 3/4" CDX plywood, after cutting to fit, coat edges with a few coats of polyurethane making sure to fill all voids etc. Secondly, apply a base coat of all weather primer and sealer to the entire sheet over the poly. Thirdly, poly entire sheet once more. I would also like to add that I am thinking about increasing the frame attachment points by extending 1/8"x2" angle between outriggers for increased integrity. Does this seem like overkill or should I approach differently?
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Old 09-01-2017, 07:05 PM   #2
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1986 34' Limited
1975 27' Overlander
Conifer , Colorado
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Hello: There are many recipes for waterproofing a plywood subfloor. The best one I have found is to fix all rainwater leaks. My 66 Trade Wind had rotted floor spots in the rear, by the front door, and under the freshwater tank. When I tested it for leaks, I found 7 that I had to repair.

I think the subfloor in your Sovereign was originally 5/8". Maybe the body is off the frame now. If the body is on, squeezing an extra 1/8" of subfloor under the c-channel would be nearly impossible.

I find polyurethane adequate as a waterproofer. Others use epoxy materials.

I don't think you need to add parameter support between the outriggers. You do need to insure all c-channel frame attachment points are solid. The aluminum body of our Airstream's is not that heavy.

The main thing is be diligent with your moisture meter and repair any leaks found right away. Keep that subfloor dry.

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Old 10-15-2017, 09:39 PM   #3
2 Rivet Member
1969 31' Sovereign
Satellite Beach , Florida
Join Date: Jul 2017
Posts: 22
Just noticed your response, apologies and thank you for the info. I am about at the point to start addressing the rest of my frame issues and your info will help a lot.
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