what type of plywood for boat floor?

[Joe D]

I am in the process of rebuilding a 1960's fiberglass boat so I can use it for fishing and hunting. I need to put a floor in, the original is gone. What kind of plywood should I use? I have read the exterior grade plywood uses the same glue as marine grade plywood, so do I really need to use marine or will exterior work. I also plane on sealing the plywood and fiberglassing it in place. It appears that is how the original was installed. Any other suggestions?

 

[GaryRI]

In this category of question - has anyone used pressure treated plywood for a floor & covered it with fiberglas?

Regular PT lumber is still pretty wet when you buy it from the lumberyard.

 

[Lou Tisch]

Easy question.....marine fir plywood.
Avoid exterior (lot of voids) and avoid Pressure Treated (POS).
Lou

 

[Chris Glennon]

What a timely thread! I'm heading to buy some marine grade plywood today to put a new floor in my jon boat. Do I need/have to seal marine grade plywood with epoxy in order to waterproof it? Is marine grade plywood more rot resistant or just less likely to delaminate?

I'm trying to figure out what benefit I'm getting by spending three times as much for marine grade plywood compared to B-C exterior grade plywood. Previously I used the B-C exterior grade plywood, sealed it with some outdoor deck sealer, pretty much saturated the cut edges with sealer and it lasted for twelve years. If I had sealed the seat screws it would have lasted longer.

By the way, I used 3/4 inch plywood last time and there was never any give in the floor. Would 5/8 do just as well? I wouldn't mind reducing the weight that I'm adding to the boat.

Thanks to everyone sharing their expertise on this forum.

Chris

 

[tgentry]

Just use the stuff you had and 5/8 or even 1/2 will work great. That is what i used in my jon and it too has lasted 15 years. That is hard to beat for the price!