My neighbor did his garage floor with that recently. I read the can, and it said not for vertical surfaces. My guess is because of the viscosity - it will tend to be heavier near the bottom of the vertical surface than at the top. I had him paint a small plywood scrap with it just to see. It cured very hard. The limiting factor is the wood of course. Works awesome on stone, concrete and I bet grout. I didn't think to try directly on foam - I should have tried that.
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Mark