Marine grade mahogany plywood - outdoor application

[David Utterback]

I have some 1/2" stored in my garage and was wondering about it's durability for an outdoors project. It looks like it should work from what I have read. Is the plywood rot resistant? Does it need exterior grade finish to last longer? My guess is that paint would likely be best. Is there a preferred one?

Thanks!

[Mel Fulks]

Sure, I'd call marine grade "rot resistant". The edges and faces need paint. Or maybe some boat coating. I would cover the exposed ply edges with
glued on canvas or narrow pieces of wood trim. But the product will last a long time ,even without that.

[Eric Schmid]

I have a trailer with wood sides I built about a decade or so ago. The trailer is used to hold yard debris, soil, gravel, etc. The side walls are marine ply. It’s just starting to wear after 10 years of essentially ground contact. So, yeah, marine ply is suitable for exterior use.

A couple of things will help longevity. Protect the edges as best you can. You can seal the edges or cap them in solid wood. Coat the ply with stain or similar. The trailer is cleaned and coated with a brew of linseed, spar varnish, pine tar...every couple of years.