Question: In the photo I sent along you can see some of the exposed plywood end-grain on my recently purchased used boat. The boat is only a couple of years old and all of the wood is in really good condition so far. I am worried though that this exposed raw wood is going to soak up water and eventually start to delaminate and stain the top finished veneer. What do you recommend to help minimise the chance of this occurring? I plan to keep this boat a long time so I don’t mind putting some effort into nailing this down before it’s a problem.

plywood end grain

In the marine environment, unsealed plywood end-grain will eventually pick up moisture and start to delaminate. Best to seal it with epoxy before that happens.

Answer: Great question. Whether or not end-grain is sealed is something I always regard as a quality indicator when I inspect new boats. Truth is, though, most production boats don't seal it, just as you show on your boat.

The best fix for this is to use an enhanced epoxy, painted onto the end-grain and then allowed to fully cure before putting things back together. When I say enhanced, I’m referring to a regular epoxy/hardener mix, with an additional additive that will need to be stirred into the epoxy to make it more resistant to eventual water penetration.

West System, for example, offers their #422 barrier coat additive. Most of these additives consist of microscopic “platelets” that sort of lie flat and create an additional barrier as water tries to penetrate the coating. Although originally intended to be used on the outside of a boat's hull to prevent gelcoat osmotic blistering, the 422 will do a great job at adding a lot of zero-maintenance years to your hard work in coating all of the unprotected wood surfaces on your boat. Understand that the additive will discolor the epoxy to a sort of light grey, but that shouldn’t matter, as those surfaces will remain mostly hidden when things are reassembled. The platelets also add a bit of abrasion-resistance to the epoxy coating, which isn’t a bad thing here as these parts may in fact be rubbing together once reassembled.

Written by: Ed Sherman
Ed Sherman is a regular contributor to, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.