cat **** BTDT, cats now steer clear of me
I've got to reply to this one. Amazing the wealth of knowledge here... . Once upon a nightmare I left my XKE outdoors with the top down. You guessed it, cat ****** on the carpet. Any time the weather got hot and humid I could still smell it no matter what treatment I used. Eventually replaced carpet/interior, then replaced car. NOT funny. No cat jokes please.
As to the suggestions above, yes the "industrial strength" Kilz or Zinzer are good products... just one additional suggestion - use some sort of surface prep on the entire area, TSP solution or other commercially available product, be sure surface is good and dry and ventilate ventilate ventilate. Finally, you didn't specify the type of subfloor, and my concern is vapor passage through to the other side and please give careful attention to the joints/edges/seams.