Who can help us investigate this smell?

[Mirroredas198]

We have a really strange smell in one upstairs room of the house. There’s no signs of water damage anywhere, the attic above the room is all in good order, we’ve cleared the room and nothing is dead/mouldy. The carpets are clean.

We’re absolutely stumped. Any suggestions? It’s driving us mad and it’s really unpleasant

Dead rodent would be my bitter experience guess, have you checked under floorboards?

How long has it been there? Could be a mouse or something similar between the walls. If it’s that, it will eventually decompose and the smell will go.

What does it smell like? Cabbage, fish, death, mould...?

It’s been like this for a few months!! Should we take up the floor boards? We can’t work out where it’s coming from, it’s just in the air! It’s a smell I can’t even describe, a bit mouldy, a bit like when they muck spread the fields.

Could be a hornets nest in the loft above the room, smells like compost, a bit mouldy. Not really the right time of year, a bit early. Essentially the hornets eat moths and insects and the rotting debris gathers on the eaves underneath the entrance of the nest and just rots. Is any of the roof plaster slightly stained?

I had this! It turned out to be food that had got stuck deep inside the hoover filter and was causing a horrible smell for a couple of weeks. Do you keep your hoover in that room?

Just to be on the safe side, have an electrical check done, especially if your wiring is a bit older.

The attic above is fine, we went up there at the weekend and had a good look around, there’s no smell up there at all.

It must be something in the wall cavity or under the floor but how on earth do we investigate it? Who would do that for us? A builder maybe?

We've been hoping the smell would eventually go on its own (as pp said, if an animal had died and was decomposing) but that surely would have gone by now.

No hoover but maybe we’ve missed something in the wardrobe. I’ll empty it out again at the weekend. I really hope it’s something straight forward like that!!

We've had problems with rats getting into our cavity walls from outside and up into the loft space. After baiting, they either leave the house in search of water and then die or (if you are unlucky) will die in the cavity wall or between a ceiling and floor. The last one that died on the premises continued to smell for 6 weeks.

A Febreze 3volution Plug in may mask it.

dead rat or rat wee

Light fitting can smell fishy if you are using a very bright bulb

https://tulsage.wordpress.com/2011/09/13/looking-around-the-house-for-that-fishy-odor/

I had this it was a dead mouse🤢
I basically turned into a sniffer dog, managed to pin point it to cupboard, even knew which floorboard needed lifted. It was a metallic, foosty smell,
I noticed it over about a week, thought it was a bin or a spill at first but no cleaning shifted it.
I went through the house methodically room by room until I found it. I was even on my hands and knees sniffing at the floor til I located it.
went away within a few hours of removing it

Could it be bats? We had them living between the wall and the wood cladding (70s style house), just underneath the windowsill.

If it's more of a sweet/rotting smell it's probably something decomposing, but that should only last for a few days. If it's more fishy it could be your electrics - you'll need an electrician to check. We had that in an old house - the previous owners had fitted (badly) spotlights in the kitchen & one was overheating.

Failing that, any possibility it's coming in from outside?

Borrow a cat! If it’s a dead rodent it will find it! Reason why we got our cat and she’s a great mouser

I had this and it was rotting leaves in the gutter outside the window. Worth a look.

Neighbours relative had this, turned out a rat had got in and under the floorboards and died. I'd definitely check underneath for something like this just incase!

I had a dead rat in my walls because of my deaf ass neighbour couldn't hear them crawling through the cavities of her walls then into mine (because of hers) it drove me mad in the end I took matters into my own hands I just went into her garden and she had TV junction boxes (large ones) that the rats were just jumping through and getting into the cavities of our homes and I locked them completely up (no one could get access)

The rats died because they couldn't get out and for about 2 weeks you could smell them but only since she truly died and new neighbours moved in I have had no issues at all.

Do you have any plants in there?

I badly overwatered a plant before I went on holiday and I could smell something wasn't right when I got home.

We once found a load of dead rotting wasps trapped in a window frame and in the loft. Absolutely foul smell.

Bed bugs can give off a rotting fruit smell too

That type of smell 'could' be dry rot, a type of fungus. I would check the joists under floorboards etc. It can spread through masonry and plaster and doesn't need moisture. It smells earthy-mushroomy. Does that sound like the smell?
Here's some info
www.trinity-rose.co.uk/everything-you-need-to-know-about-dry-and-wet-rot/

If there are any sockets near the smell it might be an idea to get an electrician out - we had an odd ‘fishy’ smell on our landing (thought it might be next door cooking but it persisted) - couldn’t work it out - then someone suggested it might be the electrics and they were right - turns out the socket on the landing was dodgy and the electrician said it could have caused a fire! He replaced it and we never got the smell again.

I had this, I had a pest control man come out and he found a dead squirrel in the loft.
There were some live one coming and going, he trapped those and took them away. Cost a fortune, he charged per head, but it was money well spent. He came several times over few weeks.
A roofer came to see where they were coming in and the little buggers had chewed the bird guard on the almost new fascias.🐿️🐿️🐿️🐿️🐿️🐿️

Thank you for all the suggestion! I’m going to work my way through them all.

Im hoping I might have figured it out though. I asked ChatGPT and it explained that if you have a sink or shower that you stop using the water trap can dry out. This works by preventing sewage smells from coming up through the pipe.

We didn’t think the shower was an issue as there was no smell in the en suite and nothing coming out of the plug whole… however!! On further investigation the water trap IS DRY!! We stopped using the en suite shower a while again when we had the family bathroom re done.

I’ve poured some water down there to fill the trap back up. I’m keeping everything crossed that this is the problem as it’s the simplest solution. I’m not entirely convinced that it is due to the smell not being in that room but in the room next to it but here’s hoping!!

I’ll return with an update.