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Home constructions and renovations

Odd odour in just one room—what could be causing it?

Anonymous user 04/08/2026 - 9:48 AM

Hi there, Hoping someone can help us out. We've been dealing with a strange smell in one of our upstairs bedrooms for quite a while now. It doesn’t seem to affect any other part of the house—just this one room. The smell comes and goes, and it's especially strong during warm and humid weather. It’s a fishy/ammonia scent, and we've already ruled out any electrical issues or problems with plastic light fittings. At first, we couldn’t pinpoint the source, but it seems like it might be coming from one corner at the front of the room, which is adjacent to our neighbour's upstairs bedroom. Over the weekend, we moved the furniture, pulled back the carpet, and took out a few floorboards. We think the smell is originating from beneath the floorboards, but we're stumped on what to do next since nothing is glaringly obvious. There’s a slight whiteness on the wooden beams, but that might just be plaster residue from the ceiling below. Can anyone offer some advice or suggest who we should contact to help us figure out where this smell is coming from and what’s causing it? It's driving us crazy! Our house is a 1930s semi-detached.

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3 Answers

Pioneer maintenance of Kitchener

Rating: 5 out of 5

Kitchener, Ontario

Good for you for opening up the floor to inspect. Humidity and warmth bring out deep penetrating stains. They can go through the floor, subfloor to the joists, the white residue suggests that. Before sanding a hardwood floor, often there is enzyme remediation for urine, blood, nail polish, remover. If not the smell you described gets 10x worse. When done thoroughly there is no odour at all. If there is an odour the $600 hepa filters in the dual motor vac need replacement. I specialize in heritage homes, have seen and smelt it all. All odours are protein and enzyme based that are eliminated by the corresponding agent.

Answered22 July 2026

Simranjeet Singh

No reviews yet

Brampton

This issue is likely attributable to moisture. Please inspect the subfloor for mold and extend your examination to include the drywall. If you find mold so treat it with RMR-86

Answered30 July 2026

Selvapriyan T.

No reviews yet

Oshawa

Based on what you've described, the smell is most likely related to moisture, mold, or a hidden leak beneath the floor or inside the wall. Since it's strongest in warm, humid weather and seems localized to one corner, I'd recommend: Inspecting the subfloor, wall cavity, and nearby plumbing for hidden moisture. Having a mold inspection performed if no obvious source is found. Checking for a dead rodent or pest activity, which can also produce ammonia-like odors. If the room shares a wall with the neighbour, consider whether a leak or issue from the adjoining property could be affecting your home. A qualified restoration contractor or mold remediation specialist can usually identify the source with moisture meters and thermal imaging before unnecessary demolition.

Answered4 August 2026