Cat & dog urine smell in underfloor heating

Urine smell baked into underfloor heating boards is one of the toughest scenarios there is — the heat cycles keep reactivating the odour compounds, and with three cats and a dog contributing over time, you've almost certainly got deep saturation in the subfloor material itself. The only products that permanently eliminate pet odours are enzyme-based cleaners — anything else just masks the smell, which means your pets will keep returning to the exact same spots. Before I point you to what I'd use here, can you tell me: are the boards sealed (lacquered or oiled) or raw/unsealed? And is the smell spread across a wide area or concentrated in a few spots?

That's really helpful. Lacquered boards mean the enzyme cleaner can't penetrate deeply through the surface, so the key is getting it into the gaps between boards and the expansion gaps at the edges — that's where the urine has been seeping and sitting. Two years of heat cycling will have crystalised the uric acid salts quite deeply into the subfloor beneath. One more thing: your Labradoodle — is it neutered? Intact males produce significantly more pungent urine and that affects how concentrated a treatment you'll need.

Cat urine is the harder problem — it's more concentrated than dog urine and contains felinine, which breaks down into particularly persistent sulphur compounds. The heat from the underfloor system is essentially running a continuous smell-amplifier. Here's what I'd use: Bio-One Pet Odour & Stain Remover. It's a professional-grade enzyme formula designed specifically for embedded, set-in pet urine — including situations where the source is beneath a surface rather than on it. For your setup, you want to apply it generously along every board gap and the perimeter expansion gap in that hotspot area, let it sit for a minimum of 20 minutes before blotting (don't rub), then repeat the treatment every other day for a week. The enzymes need repeated contact with the uric acid crystals to fully break them down. For the background whole-room smell, a single thorough treatment of the full floor surface will make a significant difference within a few days.

Bio-One is water-based and pH-neutral, so it won't strip or cloud factory lacquer when used as directed. The thing to avoid is letting any cleaner — this one included — pool and sit on the surface for a long time; the gap-and-edge application method I described limits surface exposure anyway. If you have any micro-cracks or worn patches in the lacquer, those spots may show very slight watermarking, but that would be true of any water-based product. One practical tip: after the enzyme has done its work and the floor is dry, run the underfloor heating on a low setting — it'll help volatilise any remaining breakdown products and clear them out rather than locking them in.

For a 20 square metre room with a two-year embedded problem, I'd get a 5-litre container rather than the smaller bottles. You'll use more than you think on the first treatment because the expansion gaps absorb a lot, and you want to repeat the targeted hotspot treatment several times. The 5-litre also works out considerably cheaper per litre. Keep whatever's left — with four pets, you'll use it again, and it stores well. You should notice a clear reduction in smell within 48 hours of the first treatment on the hotspot, with the background room odour fading over the following week as the floor goes through a few heat cycles.