Sealing Trailer Subfloor

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Sealing Trailer Subfloor

Postby johnwgorman » Sat Oct 15, 2016 11:54 pm

You have probably had this conversation many times but... here goes. I am building my own kit teardrop and I will need to seal the plywood underside of the base layer (subfloor). I have considered a 2 stage epoxy, spar varnish and truck bed-liner paint. I am leaning towards bed-liner because it is tough, ever so slightly flexible (less chance of cracking?) and thick. I am thinking of sealing the top side (interior) with spar varnish (tung oil based) for the VOC issue. What do you folks say?
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Re: Sealing Trailer Subfloor

Postby johnwgorman » Sun Oct 16, 2016 3:49 pm

Went to Home Depot and the attendant was a tiny trailer hobbyist. Said that he used Henry 107 Sealer and Damp-proofer on the bottom. I liked that idea... slow curing, flexible, can add on if needed in the future.
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Re: Sealing Trailer Subfloor

Postby daveesl77 » Sun Oct 16, 2016 5:03 pm

With Conch Fritter I kind of overdid it, but it works well. I used the PMF on the bottom side, first sealing the plywood with a 20% thinned mixture of TB2 and water. Let that dry, then laid on a full strength coat of TB2 to bond and applied the canvas that I had sized by washing it previously. I immediately then laid a penetration coat of TB2 on the canvas and let the whole thing dry for 2-3 days. I then put on 2 coats of Kool-Seal white elastometric roof coating, simply because I had 5 gallons of the stuff. All edges were initially sealed using the "mix", then the canvas was wrapped fully around the sandwich floor and sealed the same way as the bottom. Any holes were sealed and filled with silicone adhesive caulk. My duct access holes are wrapped with the PMF from the bottom and wrapped to the top.

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Re: Sealing Trailer Subfloor

Postby les45 » Sun Oct 16, 2016 6:01 pm

+1 for the Henrys. I used it on my weekender. Very easy to use and fairly inexpensive.
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Re: Sealing Trailer Subfloor

Postby Andrew Herrick » Wed Nov 16, 2016 1:15 pm

Now, I've heard tell of teardrops with bare undersides. Just exposed plywood or OSB. And they've lasted for years. :shock:

Do I recommend that? No. But it just goes to show that yes, waterproofing is important, but plywood's a tough son-of-a-gun.

Bedliner would certainly work. Expensive, though. An elastomeric roof coat will have more flexibility and will cost less.

Whatever you choose, just be sure to seal the edges and the wall seam. That's where campers tend to rot, anyway, not really from the underside.
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Re: Sealing Trailer Subfloor

Postby absolutsnwbrdr » Thu Nov 17, 2016 11:16 am

Asphalt fence post paint. Inexpensive, penetrating, durable, fairly quick dry/recoat time. Resists mildew, bugs, etc. Only thing I'll ever use on the underside.

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Re: Sealing Trailer Subfloor

Postby bobwhite215 » Thu Nov 17, 2016 6:40 pm

absolutsnwbrdr wrote:Asphalt fence post paint. Inexpensive, penetrating, durable, fairly quick dry/recoat time. Resists mildew, bugs, etc. Only thing I'll ever use on the underside.

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That's what I used.

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Re: Sealing Trailer Subfloor

Postby Realtoroutdoorsman » Mon Dec 26, 2016 8:21 pm

absolutsnwbrdr wrote:Asphalt fence post paint. Inexpensive, penetrating, durable, fairly quick dry/recoat time. Resists mildew, bugs, etc. Only thing I'll ever use on the underside.

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Could you paint your whole unit with it to help seal it then cover it with an oil base colored paint.


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Re: Sealing Trailer Subfloor

Postby Andrew Herrick » Wed Mar 01, 2017 11:53 pm

Realtoroutdoorsman wrote:
absolutsnwbrdr wrote:Asphalt fence post paint. Inexpensive, penetrating, durable, fairly quick dry/recoat time. Resists mildew, bugs, etc. Only thing I'll ever use on the underside.

Image



Could you paint your whole unit with it to help seal it then cover it with an oil base colored paint.



Just thinking out loud ... using two different paints on top of each other sounds like a potential compatibility issue. If you want to seal the wood, and not splurge on CPES or epoxy, why not a really good primer? It's made for just that purpose. And will help prevent staining and molding. And should have much better adhesion with the top coat than fence paint.
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