You need to try and figure out exactly were the small is coming from, and what it is.

Urine stains on wood floors usually leave marks in the finish and the wood itself (sometimes they are so bad the only fix is to replace the floor)+.
You should also check the crawl space for dead things and even leaking sewage lines.
Defects in the sewage venting system can also be a cause.

It isn't anything specific - it's not carrion smell, or the smell of feces and urine. It's just rank, allover smell, very hard to describe. Keeping the house aired out or the heat/air conditioning going helps significantly, but not completely - the smell is always there.

I guess I'll try re-finsihing the wood floors - maybe if I take off the top layer that will help, and maybe the finish applied on top will seal in whatever scent is left. At any rate, short of re-doing everything, that's all I can come up with now. Also, are there barrier films I could put down over top and install a second wood floor over that? If I do the work myself, I could maybe get this done this year (just thinking "out loud").

Thanks for your thoughts on the problem.

Verdant Croft

I used to rent out up to a dozen houses, so have some experience in odour control.

I apologize for being obvious.

But did you paint the entire house, using a sealing primer first, eg. KILZ? Throw out all fabrics, carpets and the like.

Check the attic? And every other nook and cranny? Just one mould-saturated cloth can make a whole house stink.

If there's a concrete basement floor use a powerful disinfectant, Deetol or even a commerical product, then paint and seal.

If your house was really an indoor farm, a lot of material may be trapped between the hardwood and the subfloor, as suggested above. Unfortunately, grow-ops and houses that have been home to dozens of pets often end up being torn down, as the cost is less than removing the odour and other hazards.

I have severe allergies to cats, dogs and birds and empathize with your plight. Good luck!

Have you checked the chimney?

Washed the walls?

Checked the traps for the plumbing?

Have you looked at your rain gutters when it rains? Are they draining properly and not into the walls of the house or foundation?

I'd try spraying the floors with vinegar a few times in places where I suspect urine stains. If there is urine in the wood the vinegar should help break up the enzimnes in the urines so it doesn't smell.

Checked under the stove and fridge for any surprises?

Is all the litter from the PO's gone?

You might want to feel around your walls for any soft spots. Water can get in behind walls and wallpaper especially old paper can keep you from noticing it unless you happen to run your hand across it.

diseases you can catch from the feces and urine around their nests.

Timely reminder of hantavirus dangers.

It recently killed a relative of a chat forum member I've spoken to for years. He was helping clean a rural home--including mouse nests. When he went to the hospital emergency with flu-like symptoms, he was initially misdiagnosed and sent home. By the time he was properly diagnosed and air-evaced to a larger hospital he was beyond hope and died.

A good washing is a great idea. I would also definately inspect that crawl space! Make sure no critters live or dead are there, inspect the joists and floorboards for mold, and like brickeyee said make sure there are no plumbing problems too. If you have some mold, that can be cleaned up with warm bleach water and a scrub brush. Consider putting down a vapor barrier. You could put it under the structure or put it over the dirt then maybe see about ventilation. From what I understand ventilation should be done at night and closed up in the day. Reason being the daytime air moisture could condense in the crawlspace and create more problems.

Good luck and keep at it. It took a several weeks for us to rid our strange smell in our enclosed back porch. We tackled it with a combination of cleaning out a mole nest scrubbing down what we could, putting up a vapor barrier and sealing it and plugging any holes, like where our baseboard hot water pipes were run. And now we are smell free!

You guys are great! LOTS of helpful, practical advice here. I knew if there was any way to get help on this topic efficiently it would be from the GardenWeb forums.

Many thanks to everyone!!! Now, to get started...

Verdant Croft

We had a damp musty smell in our old home, especially the basement. No water coming in but we are in a damp area. House was moved in the mid 50's part full foundation and part crawl space. We had the walls sprayed with the soy based foam. Started by doing where foundation and walls meet but DH got carried away and them do all top to bottom walls. Wow what a difference. No damp musty smell and the basement is now quiet warm as well thus making the main floor easier to heat.

I used TSP on my kitchen floor. Worked great mixed with a little bleach.