How to protect Marine Ply walls in garage from water damage?

[Andrea_S]

We have just fitted out our garage by installing insulation and marine plywood for the internal walls. Aesthetically, I am very happy with the finish of the raw plywood as it blends nicely with our epoxy floor. We do however get some water leakage at the front of the garage with heavy rain but have managed to reduce this considerably by installing a garage rubber floor seal along the bottom. Water leakage is now very minimal, but not 100% reduced.

Must we seal the marine plywood to protect it or being marine plywood, should it be able to withstand the elements such as a bit of moisture and UV?

Many thanks

Andrea

[MitchellMc]

Welcome to the Bunnings Workshop community @Andrea_S. It's wonderful to have you join us, and many thanks for your question about sealing marine ply.

Marine plywood is designed to be more resistant to moisture compared to regular plywood, so if it’s only exposed to occasional water during heavy rain and has time to dry out, it should generally hold up well. However, over time, even minimal water exposure could lead to staining on the surface of the timber. While this won’t necessarily affect the structural integrity of the ply, it can impact the aesthetic, especially since you’re happy with the natural raw look of the plywood.

Sealing the marine plywood with a clear sealer or varnish would prevent water staining and offer extra protection, but this would alter the natural appearance you like. If the water exposure is only minimal and limited to the area near the entrance, you might want to wait and see how it holds up. Replacing a single board in the future could be an option if it becomes damaged or stained, allowing you to maintain the natural look for as long as possible without compromising the rest of the garage walls.

It’s also worth keeping an eye on the water leakage. While your garage seal has helped reduce the issue, even minimal moisture over time could affect more than just the plywood, so ensuring that your water management solutions are working well will go a long way in preserving the space.

Please let me know if you have any questions.

Mitchell