The Rot Doctor


Subject: Leaking Fir Decks
Date: Fri, 03 Dec 1999

Fir decks:
Restored a 1929 7' x 30' gillnet (japanese fish boat). Eight years ago the decks were redone in fir the side decks in 1 x 12 planks. Of course the planks checked and now leak.

During the refit last I sanded decks to clean wood and used two part epoxy sealer (4 coats) and inspected to ensure the checks had been filled and the wood soaked then coated with 4 more coats of cetol 1. During the summer months no leaks but as fall approached they became sieves. Before I cover the decks over with fiberglas or some other material. Is there anything I could do differently with your products?

Bob F.
Victoria, BC

What "epoxy sealer" did you use? If it wasn't our CPES (Clear Penetrating Epoxy Sealer) then it probably wasn't a very good sealer. See the testing section of our website.

In any case, the Cetol is not a particularly good choice for fir. Cetol is not a very good waterproofing finish, and it is not particularly compatible with epoxy.

We have fir decks on our tug, and they have been coated with CPES (which penetrates deeply enough to retard the tendency of fir to check) and then over-covered with a hypalon-based decking compound called Spantex. We apply a surface coat of Spantex about every other year and the decks do not leak.

Spantex is a rubber-like compound that may not appeal to all boat people, and if we were not using that we would apply a one-part polyurethane gloss paint over the CPES-treated fir. The poly paints bond particularly well with CPES-treated wood and produce a waterproof surface. You can add traction material (sand, cork, ground walnut shells, etc.) if required. You could also use of polyurethane clear coating if the color of the wood is important -- marine grade so that it has adequate UV filter chemistry.

The key here is starting with a dry surface and making your finish build from there. With dryness you get waterproof coatings that will stand up over time and keep the water out of the wood.

Those are my opinions. Feel free to come back with additional questions. We're glad to be helpful if we can.