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I am replacing the board that goes underneath a sink's kitchen cabinet with a 1/2" OSB panel; it lies flat. (Don't ask how we got there -- what a mess!). I plan to put quarter-round around the periphery and add caulk to try and prevent water from getting into the edges.
I have a sheet of 1/2" OSB (Rated "Exposure 1") and some Minwax Helmsman Spar Urethane (Water Soluble). Should I consider putting plastic wood on the edges to help seal the OSB? Would adding solid-wood edging to the edges of the OSB, gluing with Gorilla Glue help sealing the OSB? I understand that I need to get a wax coating off the smooth surface before finishing -- my sander should do that.
If I put 4 coats of this finish on, would the resulting panel resist standing water should the faucets or disposal leak again? I would doubly apply finish to the edges. Would oil-based Spar varnish/polyurethane be the better finish choice? I don't know how to thin the water-based stuff, but, if advised to use oil-based, I would thin the oil-based finish's first few coats.
Am I OK with this approach? What would you recommend to waterproof the OSB? What alternatives would you suggest? (Min $$$)
Edited 11/9/2009 7:38 am ET by tkarlmann