Will replacing the carpet get rid of the cat smell?

Only if the urine never went past the carpet, which is unusual where a cat used the same spot repeatedly. In most houses the pad and the subfloor are holding it, so new carpet covers the odor for a few weeks and then it works through. Treat the subfloor first, then lay new flooring on top of something clean.

Why does it only smell in summer?

Uric acid crystals are not water soluble and sit dormant until heat and humidity reactivate them. Cleaning removes what is on top and leaves the crystals, so the house genuinely does smell fine in cold dry weather and strong again on the first warm humid day.

Does vinegar or baking soda work?

They help a little on fresh surface spills and do nothing for old deposits in a subfloor. Neither breaks down uric acid crystals, so the effect is dilution rather than removal, and the smell returns when the humidity does.

How do I find the spots if I cannot see anything?

A UV torch after dark. Dried urine glows a dull yellow green, and you will usually find several times more than you expected, particularly along skirting boards, in corners and around doorways. Mark each one with tape before you plan any work.

Can the smell be removed completely, or do I have to replace the floor?

In most houses it can be removed without replacing the structural floor. Carpet and pad usually go, but subfloor is more often treated in place than torn out. Replacement becomes the honest answer when urine has reached the joists over a long period.

How to Get Rid of Cat Smell From a Previous Owner

You bought the house, the cat left with the previous owner, and on the first warm day the place smells like a litter tray. This is one of the most common calls we get from new owners, and the frustrating part is that it usually gets worse before anyone works out what is happening, because people clean the surface repeatedly and the surface was never the problem.

Below is what cat urine actually does to a floor, how to find where it is without guessing, what you can genuinely fix yourself, and where it stops being a cleaning job.

Part of our complete guide to odor removal and resale value, which covers every cause and what each one needs.

The short answer

Cat urine soaks through carpet into the pad, then into the subfloor, and in older houses into the joists and the gaps between floorboards. That is why the smell survives new carpet, a deep clean and fresh paint. Removing it means finding the exact material holding it, treating that material with an enzymatic product that breaks the compounds down rather than diluting them, and sealing only what genuinely cannot be cleaned. Warm humid days make it worse because heat drives the residue back out.

The smell is in the pad, subfloor or joists, not on the surface you can see.
New carpet over an untreated subfloor traps the odor for a few weeks and then it returns.
A UV torch after dark finds the deposits far faster than your nose does.
Enzymatic treatment breaks the compounds down; masking and shampooing only dilute them.

Why it survived the clean and the new carpet

Cat urine is not a surface stain. A cat returning to the same spot over months or years deposits far more liquid than a carpet can hold, so it passes through the fibres into the pad underneath, then through the pad into whatever is below. On a plywood or chipboard subfloor it soaks in. On older boards it runs into the seams and down the sides of the joists where nothing can reach it.

The compounds themselves are the second half of the problem. As urine breaks down it produces uric acid crystals, which are not water soluble. Washing dilutes what is on top and leaves the crystals in place, dormant. Then humidity arrives, the crystals reactivate, and the smell comes back exactly as strong as before. That is why so many people describe a house that smells fine in February and unbearable in July.

It is also why replacing the carpet so often disappoints. New carpet over an untreated subfloor seals the odor in for a short while, then the residue works through the new pad and you have paid to relocate the problem.

Find it before you treat it

Guessing wastes money. Locating the deposits takes about twenty minutes and changes the whole job.

Wait until dark. A UV torch shows dried urine as a dull yellow green glow. It has to be genuinely dark for this to work, so close the curtains or wait for night.
Sweep low and slow. Hold the light close to the floor and work in strips. Check along skirting boards, in corners, behind where furniture stood and around doorways, which is where cats mark most.
Mark every spot. Painters tape around each one. You will almost always find more than you expected, and the pattern tells you whether this was one incident or years of habit.
Check the perimeter of the room. Urine tracks toward walls and under the edge of the carpet, so a deposit that looks small on top is often much larger underneath.
Lift a corner if you can. Pull back the carpet at one marked spot. The state of the pad and the subfloor tells you immediately whether this is a carpet job or a floor job.

The heat test

Shut the room up on a warm day with the heating or air conditioning off for a few hours, then walk in from outside. Heat and still air push the residue out of the material. If the smell is far stronger than usual, the odor is in the structure rather than on it.

What you can do yourself

If the deposits are small, recent and confined to carpet, a thorough enzymatic treatment can genuinely finish the job. Enzymatic products work by digesting the compounds rather than covering them, which is the only DIY approach that addresses uric acid crystals.

Saturate, do not spray. The product has to reach as deep as the urine did, which means far more liquid than feels reasonable.
Give it time. Enzymes need hours, not minutes, and drying it too fast stops the reaction before it finishes.
Do not use a steam cleaner first. Heat sets the proteins and makes the odor harder to remove permanently.
Skip anything perfumed. You will end up with cat urine and air freshener, which is a worse smell than either.

Where this stops working is depth. Once the urine is in the subfloor or the joists, no amount of product applied from above reaches it, and the honest answer is that the material has to be treated directly or removed.

When it needs a professional, and what that involves

Call someone when the deposits are widespread, when they have soaked past the pad, when the house smells worse on warm days despite a deep clean, or when you have already replaced flooring and the smell came back.

Find the source properly. Every affected material gets identified before anything is treated, including under the edges of the room where the carpet meets the wall.
Remove what cannot be saved. Pad almost always goes. Carpet often goes. Subfloor sometimes gets treated in place rather than replaced.
Treat the material itself. Enzymatic and oxidizing treatment applied directly to the subfloor and joists, not sprayed over a covering.
Scrub the air and the HVAC. Hydroxyl generators with HEPA and activated carbon, plus duct cleaning, because a house recirculates its own smell through every vent.
Seal only what is left. Sealing is the last step, applied to material that cannot be fully cleaned. It is not the strategy, and it is not a substitute for the four steps above.

We never use ozone and we never use chlorine. Everything is green and non toxic, safe around children and pets, and most homes are finished in 1 to 4 hours.