Waterproofing Plywood That's Not Below The Waterline

[Bassyak]

I've searched the internet for help on this and haven't found much, so I thought I'd poll the group here.

I've constructed a new tackle box to sit on the deck of my Tracker ProTeam 175, between the driver's console and the front deck, roughly 42"x 15" x12". There was some unused space there, so I took some scrap construction grade plywood from the trash bins at a home building site next door and built a box to fit and basically be an extension of the casting deck.

My problem comes in how to seal it to keep the plywood from getting soaked (and the tackle inside it) if I get caught in a hard rain. The boat is garaged and the box is just going to be sitting on the deck, so never exposed to water other than rain or from normal fishing activities. I plan to carpet the lid and front edge to match the carpet in the boat. The other sides will just be painted or sealed or both.

I'd like to do this on the cheap as I don't have a lot of extra funds (or the expertise, for that matter) for an expensive epoxy or resin job. I'd like to find something readily available locally that I can brush or spray on that will do the job sufficiently. Or is this something I should even be worrying about, since this thing won't even see the water really?

Any help would be appreciated....thanks guys

Bassyak

[Fishing Rhino]

Fiberglass it, inside and out, then paint it. You need to paint it because the commonly used fiberglass resin is polyester. It will absorb moisture. Paint will seal it. Vinylester resin is waterproof, but not commonly available.

You can also coat it with Gluvit, an epoxy product.

Before applying anything, be it fiberglass or Gluvit, Fill all the knots and imperfections with bondo.

Construction grade plywood, while made with exterior glue is notoriously porous and rough. It's fine for sidewalls, subflooring and roofing, but not much else. It's made to be "economical", and used in places where cosmetic blemishes and imperfections do not matter.

Do not coat it with fiberglass resin only. It will not last.

[Way2slow]

I've got some stuff a local company that's a customer of mine gave me. It's a thin, 2 part epoxy that soaks into the surface of the wood and makes it totally waterproof. It's used on wooded surface of yacht's. It can also be painted over when dried. I can see if there's a name on it but, it retails for about $200 a gallon if interested. Sure is nice to have friends, he gave me enough to make five gallons.

[Polarkraft05]

if you use treated (cca) plywood i dont see why you would need to go all out and cover it is resin/ glass etc. as you put it it will never be exposed to anything other than rain, or occasional splashing.

cca treated wood is used for decks, and holds up fine in outside conditions which is what your box is going to be put through except less since you said it is garaged.

the best way to protect a deck is to use a water sealant of some kind, but many decks are simply just cca wood and thats it, and they last for a long time.

if the box was going to be under constant water exposure it would be a different story.

[slonezp]

$19.99 and if you have extra, you can spray it on a screen door and use it as a backup bass boat.

[Gavin]

_{Spar Varnish...you can pick up a gallon for $40 or so.}

[J Francho]

Way overcomplicating this one.....any exterior grade paint will work.

[deaknh03]

  On 2/3/2012 at 7:04 PM, J Francho said:

Way overcomplicating this one.....any exterior grade paint will work.

and seal the joints with outdoor grade caulk, usually the one that says doors and windows, $3.99.

[A-Rob]

I built a plywood deck for my tin boat.

I was going to get fancy and seal it with epoxy/paint/carpet but I ended up buying Thompson Water Seal. It cost me 13 bones and works phenomenally. It is supposed to be for decking or vaneering.

The other reason why I did it with this is b/c in the offseason I just lightly sanded it to get the dirt off and rough up the finish slightly then I sealed it again.

It is "bare" plywood and has lasted me years.

You can use your left over sealant on your deck haha

[Bassyak]

J Francho, on February 03 2012 - 02:04 PM, said:

Way overcomplicating this one.....any exterior grade paint will work.

"and seal the joints with outdoor grade caulk, usually the one that says doors and windows, $3.99."

^^^^^

These things are in line with what I was thinking, but I didn't know if it was enough. Thanks for all the suggestions so far. What about products like the cans of Rust-O-Leum rubberized undercoating or truck bed liner that you can get at Lowes? Or Plasti Dip? Would they work on wood or are they not worth the trouble?

If I used the Thompson's Water Seal, can I still paint it after that?

[Professional Overrun]

Best cheapest thing you can use is rustoleum appliance paint. It a single part epoxy esther resin paint, so no mixing two parts. I built a plywood fishtank and painted it inside with that paint and it held water for six months! It sat in my living room with some fish i couldnt house in it. Wonderful product, and its only like $15 a quart at home depot, also comes in rattle cans.

[tritonguy]

I use spar urethane.

[00 mod]

Best thing I have ever used is spar urethane and then paint over it!

Jeff

[barroncooper]

I would use RedGard. It's a paintable latex that I use for sealing walk in showers. I would just use a paintbrush and paint it on. this stuff is about 35 -40 bucks a gallon and is good to have on hand. I think they make smaller sizes maybe a pint but not sure. goes on pink and dries red. but is paintable.

[A-Rob]

  On 2/3/2012 at 8:32 PM, Bassyak said:

If I used the Thompson's Water Seal, can I still paint it after that?

Yep you can pain over it, I think you need to wait up to a week (depending what type of paint you use) to let the Thompson water seal set.

I was going to paint mine over top as well but decided not to b/c it would be easier to resurface every off season and re seal...But I was going to paint mine and put some sand in the paint to give my deck some grip.

[Bassyak]

Anyone ever use products like the cans of Rust-O-Leum rubberized undercoating or truck bed liner that you can get at Lowes? Or Plasti Dip in the spray can? Would they work on wood or are they not worth the trouble?

[Mitchell Jonker]

Adding to this I’m building a casting deck on my 16ft Starcraft aluminum. I want to waterproof the plywood I used before i put marine grade carpet on it. Just in case of leaks or heavy rain etc. In hindsight I should have used marine grade plywood but I was trying to save some money.  Now the glue I have to use for the carpet will adhere to almost anything but some plastics and rubber. So using “liquid rubber” of any sort won’t work. Any suggestions would be appreciated.

[MN Fisher]

  On 5/6/2020 at 12:46 AM, Mitchell Jonker said:

Adding to this I’m building a casting deck on my 16ft Starcraft aluminum. I want to waterproof the plywood I used before i put marine grade carpet on it. Just in case of leaks or heavy rain etc. In hindsight I should have used marine grade plywood but I was trying to save some money.  Now the glue I have to use for the carpet will adhere to almost anything but some plastics and rubber. So using “liquid rubber” of any sort won’t work. Any suggestions would be appreciated.

Expand  

Already mentioned above - but again.

[Mjmj]

On another forum (which is about redoing aluminum boats) they suggest using

OLD-TIMER S FORMULA 
One part Boiled Linseed Oil, 
One part Spar Varnish or Spar Urethane.
Two parts Mineral Spirts.

It's cheap and lasts forever
 

Also never use (regular) pressure treated wood on a aluminum boat 

[Quarry Man]

do not use [ressure treated wood, its heavy and not meant for water, mainly insects, it will corrode aluminum. Don't use sob, its not meant for structural support. Use rustoeum oil based enamel, there coats and you should be good. The oil is a lipid which are naturally hydrophobic, kinda like oil and water science experiment.