treated or marine plywood

captain don · Post by **captain don** » Fri Jul 31, 2009 4:56 am

I have been a general contractor all my life and feel a little funny asking for advice on wood but treated wood was not out when some of the older boats were made. Also I have not used marine plywood that much to see really how it holds up. Any thoughts about the lasting qualities of treated plywood verses marine plywood. I'm not talking how pretty it is or how smooth, just lasting quality say below deck out of sight. Thanks, Capt. D

prowlersfish · Post by **prowlersfish** » Fri Jul 31, 2009 6:46 am

Marine plywood is much stronger you should not paint or glass treated wood I have been told . Marine plywood would be my choice my boat has a lot of it, floors bulk heads etc . 30 years old and in good shape.

Marine plywood is costly but well worth it

randyp · Post by **randyp** » Fri Jul 31, 2009 10:41 am

Marine plywood should not have any voids between the laminated layers, as most likely is the case with treated plywood. Marine plywood is stronger and the grain is cleaner/clearer for interior work.

Mac32 · Post by **Mac32** » Fri Jul 31, 2009 11:13 am

Did allot of research when making new laminated stringers for my boat and nixed the idea of treated plywood quickly due to poor bonding issues with epoxy because of the CCA or ACQ treatment. Plus it was less dense (weaker) due to fewer layers and more voids, may also be lower quality?

chucka · Post by **chucka** » Fri Jul 31, 2009 7:34 pm

I built a hard top from marine plywood in the spring of '08. I sealed the edges with epoxy resin and painted it with multiple coats of topside paint over a primer coat. I was disappointed that within a few weeks of exposure to the weather, the grain opened up creating many hairline cracks following the woodgrain, in the paint. I think if I left it exposed the top ply would have delaminated pretty quickly over time. This season, I sanded off the paint and put down one thin layer of glass cloth with resin to stabilize the wood grain. Followed again by multiple coats of topside paint over a primer coat. So far so good this season.

I agree completely on the comments above about marine vs. treated, but if you use marine plywood exposed to the unprotected marine environment, it needs more than paint for a finish.
Chuck