Sealing untreated plywood

[cavman138]

I'm going to be putting a deck on my jon boat and have read a lot about people using marine grade plywood or using regular, untreated plywood and sealing it with something like thompson's water seal. Any idea how well this would work? The boat is going to be in mostly freshwater, but I will take it to the hot ditch and a few other places in saltwater.

[dwkoller]

I'd stick with marine plywood. The glues holding the wood layers together are designed for a marine environment. Thompson's or other wood sealers only treat the surface layers.

Marine plywood is about 3x the cost of standard plywood. The time and effort you're going to put into this project is worth the more expensive wood. I'd even seal the marine grade plywood with epoxy resin and fiberglass cloth.

Take your time and do a quality job.

[Tom Powers]

Pressure treated does have it's place.

How long to you want it to last?

Do you intend on sealing it with fiberglass cloth and epoxy or just gluing carpet to it?

Describe your boat a little better. Length, width, partial deck or flooring? On either type of deck how much.

Pressure treated soaked in something like Thompson's water seal or a good quality exterior stain will hold up for a few to several years, but sooner or later you will have to replace it again.

Do it right with marine plywood coated on both sides with fiberglass cloth (10 oz bottom 32 oz on top) and epoxy and you will not have to worry about it until much later. . .