The Rot Doctor


Subject: Wood Finish
Date: Fri, 13 Jun 2003

Hi Rot Doctor,

I have a problem like one of your previous FAQs but with a variation: I lifted the bathroom linoleum and found slight water ingress to the wood floorboards from the shower. I am currently drying out the floor out with ventilation. The floorboards seem sound but have some white presumed fungal discoloration at the edges, however this only seems to be only on the surface when scratched. The room has a noticeable odor which I guess may be dampness or fungal growth.

Ultimately I intend to sand all of the old varnish finish off the floor and treat the wood with a clear oil based seal. My local store recommended bleach or CPES as a rot/preservative treatment against fungal growth, however can I expect either to discolor the sanded fir wood floor? Also does it help with presumed damp odors?

I would very much appreciate your advice.

You have some slight fungal growth, but no rot. Had you not caught this, however, it would almost certainly have developed into rot.

CPES (Clear Penetrating Epoxy Sealer) is the ultimate preventative against rot. All our testing shows that wood that has been treated with CPES will not rot, regardless of moisture levels and heat. Applied to clean, sanded wood, CPES tones the wood to the same extent as a coat of clear varnish...that is, it highlights the grain patterns. Makes the wood look quite lovely, actually.

But CPES is an epoxy, and epoxies will inhibit the ability of the wood to absorb an oil-based sealant. Generally a clear polyurethane coating is applied on top of CPES-treated wood, or varnish. These will bond with the CPES-treated wood and produce a durable finish. For best bonding, the top coating should be applied as soon as the CPES'd surface becomes dry, usually sometime within 12 hours after application.

CPES will eliminate any damp odor smell. During application and curing, however, CPES produces strong organic solvent odors and the bathroom should be closed off and vent fans turned on or cross ventilation provided through open window(s). A respirator capable of filtering organic solvent fumes should be worn.

If you are set on the oil-based sealer, we recommend that you wipe the floor down with a mild solution of bleach and water. Do this first, and then come back and sand to clean wood. And then apply the oil sealer. If the floor is kept dry after this, you should have no rot problems.

Hope this is some help, and feel free to come back if you have additional questions.