I'm trying to fine a way to make my stairs scratch proof, so you can scratch it with your finger nail, so the dog wont mess them up. Polyurethane wont work as mfg do not recommend putting it on existing painted surfaces. The paint I used was Valspar Latex Porch Paint (with Zap Primmer). I recently purchased Gidden Polyurethane Oil Gloss Paint and put some on a test piece. I do not think it will harden well enough to prevent it. The wood I used was your standard wood, specifically made stair treads, ready to paint from Lowes. I didn't buy Oak, which is a much harder wood. The only solution I can think of, is assuming the Gidden stuff does harden pretty well, I should take the boards up and put down oak & use the Gidden stuff, so the paint hardens nicely and the wood underneath isn't soft, but hard as well.
Any suggestions or comments from your experience is greatly appreciated!