Wood Deck Sealant

[CaptErv]

I know there’s all kinds of threads about best methods for sealing wood already on here and on many other websites. I’ve read just about everyone already.

But I want to get your opinions on my situation. I am replacing the cockpit flooring in my Alumacraft and already have the cut pieces of 3/4” marine ply (yikes was it expensive). The topside of the wood will be covered with Marideck vinyl but I want to seal the underside. The underside is in close proximity to the floatation foam which was previously waterlogged (replaced) and gets no sunlight exposure. There isn’t much opportunity for this wood to breathe underneath the deck.

I’m thinking of just doing a couple coats of oil based exterior enamel with the first coat being thinned by 10% with extra coats on the edges.

Am I crazy? I don’t really want to spend the $ on epoxy. Polyester resin sounds like it has adhesion problems. Spar could work but since I don’t care about looks I am leaning to just oil based paint? The added flexibility of spar could be good though. Cabot Timber Oil doesn’t make sense for a constantly wet/humid area? Old Timers formula scares me with drying times. Could be 3-4 weeks before everything is fully dry and ready to be installed.

Thoughts?

 

[FuzzyGrub]

I used oil base primer and paint when I replaced the floor in our 14' Starcraft. It did not hold up. The foam that was in contact with the floor, rotted the ACX plywood, over time. I blame myself for reusing some of the old foam that appeared to be good. But, even with all new foam, would not use that method again.

I'd use the epoxy or resin on the underside and edges. Maybe use the "old timers" brew for the top, if glue adhession is the concern/problem.

 

[CaptErv]

I used oil base primer and paint when I replaced the floor in our 14' Starcraft. It did not hold up. The foam that was in contact with the floor, rotted the ACX plywood, over time. I blame myself for reusing some of the old foam that appeared to be good. But, even with all new foam, would not use that method again.

I'd use the epoxy or resin on the underside and edges. Maybe use the "old timers" brew for the top, if glue adhession is the concern/problem.

Thanks for the info Fuzzy. I am concerned about the foam being in constant contact with the wood and accelerating the rotting like what happened with yours. I tried to cut it down to allow a small space between the ply and foam but it’s not perfect.

 

[FuzzyGrub]

Thanks for the info Fuzzy. I am concerned about the foam being in constant contact with the wood and accelerating the rotting like what happened with yours. I tried to cut it down to allow a small space between the ply and foam but it’s not perfect.

With 3/4" ply, you probably don't need any support from the foam. A 1" gap would be good. As a minimum, I'd still do the "old timers brew" over oil primer and paint. Getting hard to get oil based paint, here in NY.

 

[LDUBS]

One pint of Total Boat penetrating epoxy is about $40. A quart is just under $60. Thin with DNA or acetone. One pint covers up to 40 sqft. Double that for a quart. Unless you have paint/primer on hand, it seems that cost is comparable. I used several coats of it on a generator cover for a travel trailer. Pretty easy to use. No problem painting over it after scuffing it up with light sanding.

 

[thill]

I soak all of my plywood, especially the edges and cut areas with Thompson's Wood Preserver/Waterproofer. You need at least two soaking coats, as it absorbs completely into the wood. I generally do three applications, and if there are areas that aren't soaking on the third application, I use the roller to spread it over to other areas. You want it really sealed well.

Once it dries, the wood looks like nothing has been applied to it, unless you sprinkle water on it, which beads up like on a freshly waxed car.

In my experience so far, any exterior carpet glue or solvent-based adhesive adheres well after waterproofing. I've used Titebond III to adhere transom layers together, and it made a solid bond, and I have used carpet glue type that cleans up with water before it dries, as well as solvent-based Henry and they all worked well.

Thompson's is inexpensive and has been flawless in performance for me. Wherever I used a fastener, drilled or cut after installation, it only takes seconds to soak that area using a brush or rag to ensure good protection.

I've also used epoxies, both thinned and un-thinned, and they work fine, but are expensive, and I haven't seen any better results with them.

 

[TNT-fishing-]

I used Bondo fiberglass resin on transom and deck boards then used Total boat total tread topside.

 

[Douglasdzaster]

X2 on the Total Boat penetrating epoxy. I used untreated plywood for the floor in my rebuild. Used TB on both sides edges every where. Fist coat after mixing the two parts I added acetone to 50/50 the mixture. It really soaked in.
My plywood is on top of 2” foam board insulation and I used snaps to attach carpet on top.
I pulled back the carpet not long ago and the plywood looked like it did when I installed it.
Total Boat makes good stuff. That floor will outlast me.