In this Q-and-A column, we discuss how to treat stubborn pet odors that have gone beyond the carpet and padding, and which products (homemade and commercial) to consider.

Q: I have an in-law apartment that I foolishly rented to a person who had two cats. One or both cats apparently had a lot of accidents, because even a year after she left I can still smell the cat urine.

I’ve replaced both the carpet and padding. Do I need to rip up and replace the wood subfloor also? I did not treat the wood with any chemical before I replaced the carpet and padding. I thought it would not be necessary.

A: We’re guessing that you now have a “no pets” clause or a hefty pets deposit in your lease agreement.

Unfortunately, you made a mistake by not treating the subfloor when you replaced the carpet and padding. The damage has been done. Parts of the subfloor and the padding will have to go, and maybe the carpet, too.

When cats and, for that matter, dogs, do their business in the house, they tend to go in the same place. Which means, with any luck, that the problem is localized.

When pet urine dries, it forms crystals that produce a stench. You were right to replace the carpet and pad, but urine soaked through the old carpet and pad and into the wooden subfloor. The odor you smell is from the crystallized urine in the impregnated wood.

You probably don’t need to replace the entire subfloor. Pull up the carpet and pad and search the subfloor for urine stains.

In some cases, it is impossible to get urine odors out of wood. So, to be safe, cut out and replace the stained sections; treat the rest of the subfloor with a cleaner specially formulated for pet urine; and replace the pad.

It’s worth trying to salvage the new carpet, but there’s no guarantee that the odor hasn’t impregnated the rug. If that’s the case, a carpet-cleaning professional will have the right chemicals to neutralize the odor.

Cleaning cat urine effectively depends on a number of factors, such as where it’s located, how long it was left unnoticed and the type of surface it was deposited on. In this case, it’s been in the wooden subfloor for a long time.

The better cleaners contain enzymes that break down the urine and neutralize the odor. Usually, the first step is to take a rag or wad of paper towels and firmly press it into the area to soak up as much urine as possible. Obviously, your renter didn’t do this.

There are a number of options for cleaners at your local pet store. When using a commercial product, follow the instructions.

Some products you might ask about include: Zero Odor, Anti-Icky-Poo, Nature’s Miracle, Odorban, Odornil, Nilodor, and Cat-Off.

Here are several homemade cleaners you might try, although given the situation, we’d go with a commercial product.

  • Hydrogen peroxide. Spray 3 percent hydrogen peroxide on the spot and let sit for a few minutes. Blot dry with a clean cloth.
  • For a stronger solution, mix 3 percent hydrogen peroxide with a squirt of dish soap and a sprinkle of baking soda. Spray this mixture on; let it sit for a few minutes; then blot dry.
  • White vinegar. Create a warm-water dilution with 25 to 30 percent vinegar. Spray this mixture on; let it sit for a few minutes; then blot dry.

Note: If you use any of these solutions, it’s a good idea to test them first on a piece of scrap carpet or an out-of-sight area of the floor to ensure they don’t cause damage.

Finally, avoid products that contain ammonia, as the odor of ammonia is similar to the odor of urine.

Email Inman

Editor’s note: This article was originally published on Inman in 2012 and has been updated. 

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