Floor vapor barrier or sealer question

[SPLAT]

First of all we get a lot of rain and moisture around here...
My teardrop kit came with a vapor barrier to be glued on the bottom of the plywood sheet/floor... The problem is this barrier is like a woven mesh, it is porous and when I put water on it leaks through.
What do others use to protect the underside of their plywood?

[noseoil]

I used some of the "Henry's" white roof coating, which is common here in the southwest. It would be best to put a layer in place with the plywood upside down (thick nap roller is quick), bed the membrane into it when it's wet, then coat the surface on top with more. This way it's "locked" in place & will create a pretty good moisture barrier. Any penetrations for bolts, wires, pipes, etc. are points which should also be treated when doing the build.

How did you apply the mesh?

[SPLAT]

I was goibg to use 3M 77 spray glue...

[les45]

+1 on the Henry's. I used the black stuff on my build. It says on the can that it might not be compatible with some plywood so I gave the bottom of my floor two coats of Zinsser primer first and then one coat of the Henry's. No problems with delamination or anything. With the Henry's you probably don't need the vapor barrier.

[SPLAT]

+1 on the Henry's. I used the black stuff on my build..

What is the name of the black henrys product you used?

[les45]

What is the name of the black henrys product you used?

I used Henry #107. It is an asphalt emulsion for general waterproofing. It is kind of messy if you are not careful with your application so use a drop cloth. I used a brush and applied it horizontally before I flipped the floor over. I may have given it two coats over the two coats of Zinsser. I did a quick internet search and it looks like it may be harder to find now. I didn't see it at HD or Lowes online. Check the roofing sections at those stores and they may still carry it. You can get it at other web sites too. Google search "Henry #107 one gallon" and you will find several sources. Prices are all over the place but you should be able to get it for under $20. It goes a long way. I'm still using what's left of mine to coat trees where I cut the larger limbs off.

[daveesl77]

For Conch Fritter we first sealed the bottom layer of plywood with the "mix". We then glued on canvas, then covered that with kool-seal (an elastometric roof coating). Once it all hardened it takes a saw to cut it and it refuses to budge. Hit it with a hammer, nothing. Absolutely sealed.

dave

[noseoil]

I would not use 3M 77 for your membrane. The idea is to encapsulate the wood with a waterproof "skin" which soaks into the wood & then covers the surface. The Henrys stuff is pretty good, 107 asphalt emulsion is used on roofs, concrete foundations & other things. The 208 is wet patch for wet areas on a roof. They make a bunch of different stuff...

[SPLAT]

FYI, I went with the Henry's 107 and it turned out real nice

[coyote]

I was advised and went with Kilz. 'The adviser said use the original one. (not water clean-up/non-smelling kind) We get tons of rain here during "camping" time, lots of miles in the last 2 1/2 years. Still looks like it did when I put it on. No problems so far. It also lives out under patio while next project takes garage. Dave