Goedjn wrote:
If you're about to rip up the underlayment anyway, why not
give one of those enzyme cleaners a try? If it screws
up the pressboard, you're no worse off than before.

In my experience, the enzyme cleaners aren't effective because part of
what you're fighting are crystal deposits in the wood which do not
dissolve no matter what you use.

You should see what several years' worth of dog pee did to the hardwood
floors in a house a friend of mine bought. We scrubbed, bleached,
enzymed, stripped the floors, all to little avail. The crystals were
deep in the fiber of the wood, and nothing was getting them out.
Finally, we applied a couple coats of polyurethane, and the stains are
still there and dark-ish but not too bad and there's no smell. The
floor even looks like it has some character instead of looking like it
was a dog's bathroom.

Check the baseboards and bottom few inches of drywall
while you're there.

Good advice. See what is or is not going on that you wouldn't otherwise
discover until it's too late.

(Hmm.. note to self. If ever buying rental property,
seal the floors before letting tennants [sic] in...)

Definitely. One should always take a careful, thorough, paranoid
approach to investment properties. Oh, and remember: they're going to
be your tenants, not your new friends.

What? That's just me? (sigh)