Cat urine smell comes back after washing because it is produced by crystals that water does not dissolve.
Pet urine is not simply a liquid with a smell. It contains urea, uric acid salts and proteins. As it dries the water evaporates but the salts remain and form crystals that bind tightly into the pores of the material. These crystals are almost insoluble in water — which is exactly why ordinary washing does not carry them away.
Two things then happen. Bacteria break down the urea, releasing ammonia — the sharp, biting smell you notice immediately. At a later stage of decomposition, sulphur compounds form and give that persistent, sickly-sweet note people describe as “old cat smell”. It is this second stage that lasts for years.
And now the key practical fact: these processes need moisture. When the floor is dry the crystals lie dormant and the smell is faint. When you wash the floor, the moisture partly dissolves the crystals and bacterial activity restarts — the smell becomes distinctly stronger for a few hours. The same happens in damp autumn weather and in summer heat.
If the smell gets stronger after you wash the floor, the source is right there and has not been cleaned out.
Liquid follows gravity and gaps. On a smooth surface it runs to the nearest joint and then travels down and sideways, under the covering, along the inside of a skirting board, sometimes as far as the bottom edge of a partition wall.
| Location | Is surface treatment enough |
|---|---|
| Tiles, laminate (surface) | Usually yes |
| Skirting boards and their gaps | Often has to be removed |
| Under laminate or linoleum | No — the covering has to be lifted |
| Rug | Often no — depends on the backing |
| Soft furniture | Ozone treatment + surface treatment |
| Base of a partition wall | Often no — the board absorbs it right through |
| Concrete base | Needs treatment that soaks into the material |
If the smell is strong but there is no visible stain, it usually means the liquid has got under the covering or behind the skirting board. In that case surface treatment does not help: you are treating the top of the laminate while the source sits on the concrete base underneath it.
Two places are missed most often. The first is the inside of the skirting board — liquid wicks up into its lower edge and stays where it can neither be seen nor wiped. The second is the base of a partition wall: the bottom few centimetres of plasterboard or fibreboard absorb liquid like a sponge, and the crystals sit right through the material.
A three-room flat where a cat regularly missed the tray in one corner over the past few years. All that is visible is a small stain on the laminate. Lifting the covering reveals a patch about a metre across on the foam underlay and the concrete, and the skirting board has to be replaced. Surface treatment here would have given a result lasting a week.
Before you order anything, it is worth working out the scope yourself — that determines whether this is about one corner or the whole room.
One more signal tells you a great deal: if the animal keeps choosing the same spot, the source is definitely there. What draws the animal is precisely its own earlier scent, which you can no longer smell but it can perfectly well. Until the crystals are removed, the spot stays “marked”.
Cat urine is the hardest case, but not the only one. Dog smell in a room arises differently: it mainly comes from sebaceous secretions on the coat that settle onto textiles, soft furniture and rugs and oxidise there. It is distinctly a “surface and textile” smell, so ozone treatment together with washing the textiles usually gives a good result without lifting the floor.
With small pets — rabbits, chinchillas and birds — the problem is usually local: the cage, the area around it and the wall behind it. Treating that spot and ozone-treating the room is enough, unless liquid has been running onto the floor under the cage for years.
What determines the scope of the work and the price in practice:
Three things increase the scope: how long the situation has been going on, how porous the covering is, and whether liquid has got underneath it or into a partition wall. One spot on tiles is a short job. Several spots on laminate with a soaked base means lifting the covering, and that is a different scale of work — which we determine during the inspection, not over the phone.
We establish exactly where the affected spots are — often they are not where the stain is.
We tell you whether surface treatment is enough or the covering has to come up.
We treat the affected spots with products that act on the source of the smell.
We treat the room, the soft furniture and the textiles.
We air the premises and make sure the smell has not come back.
And the honest limit. If liquid has soaked over a long period into a porous concrete base or a partition board, there is a scope beyond which treatment is no longer economic. Replacing the material then costs less than two or three repeat treatments with partial results. Where that limit lies is visible on site — and we tell you before the work, not after.
Ozone treatment €1.20/m², minimum €60. If surface treatment or removal of the covering is needed, we set the price after an inspection. For larger cases see also Disinfection after keeping animals.
If the liquid has not got underneath the covering, yes. If it has soaked in deeper, surface treatment gives only a short-lived result, and we tell you that straight away.
During ozone treatment neither people nor animals may be in the room, and an aquarium has to be taken out or sealed. After treatment and airing, animals can come back — we give the exact time on site.
Because the urine salt crystals are almost insoluble in water, while moisture reactivates them. It is a clear signal that the source is still inside the material, not on its surface.
Describe the situation — we will tell you whether treatment is needed at all, and which one.
Fill in the form — we will call you on the number you provide, ask a few clarifying questions and propose a solution.
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