Just recently bought a house which has been renovated. It was in a pretty poor state beforehand however since we've moved in (house has been vacant for 7 months at least) the main bedroom has a terrible smell.

I've used rug doctor on the carpets and noticed no change, and today have since looked at the walls in the room and noticed they're carrying the smell.

It's an end terrace & I've also checked all bathrooms and drains no signs of mold or smell from any of them which tells me we may have a damp problem or something else in the walls?

The smell is very strong so we've moved no furniture into it it's just empty. What do you think this could be and who exactly would we call to come and sort/solve this problem please?

Any help would be much appreciated! Thanks

  • 3
    Most house drains(sinks, tubs,toilets) have what is called a P-trap under them. This trap holds some water to prevent sewer gases escaping into the house. These can dry out over a couple of months and let sewer gas in. Seven months is long enough it might be something else also.
    – crip659
    Apr 6, 2022 at 19:16
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    Depending on which country you live in, and if hollow double walls are a thing there, a rodent could also have died inside. They'll dessicate over time, but until they do there'll be a strong smell.
    – MiG
    Apr 6, 2022 at 19:30
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    Sick I can imagine with a strong smell, dizzy makes me a bit concerned about the health effects of the source. I would consider getting an environmental inspector of some sort to check this out, or someone with a boroscope check the insides of those walls. Perhaps you could temporarily sleep downstairs until you've resolved this?
    – MiG
    Apr 6, 2022 at 19:47
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    Yes thank you we've got someone coming out next few days who suspects it's not damp due to the smell we have described but we will see what they say.. After the first night we moved the bed out and into the back room so haven't slept in there since want to get it sorted asap as I'm 7 months pregnant too so it has been worrying... we're first time buyers too so we took out a homebuyers survey through a conveyancing company I'm surprised that this wasn't flagged too us , feeling a bit disheartened right now.
    – Sophie
    Apr 6, 2022 at 20:03
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    With today's energy prices you'll definitely want to get that one fixed - cavity wall insulation is pretty fine and you might also be able to get a grant for it. Given that your walls have an empty void in them then it's pretty likely to either be something died or there's mold in there - the person coming over should be able to see inside and find out for sure :) Apr 6, 2022 at 20:25

1 Answer 1


Firstly, get someone to perform a diagnostic

Air quality in a building can be very dangerous if unchecked (particularly sewer gas, but also carbon monoxide which is odorless). As it's not particularly clear what type of smell it is, you do need someone to be on site to whiff around who knows (nose? sorry) what they're up against.

Note that in order to sell a property in the UK, an assessor would have performed various checks so it is very unlikely to be something critically dangerous but we can't say for sure here.

Possible causes, quick wins

Sewer smells

Sewage has a very distinctive smell. If you're not sure if it's this, find a nearby water treatment plant and you'll get to know the smell fairly quickly. Sinks and drains have a bend in them which contains water to hold back sewer gas, but sometimes this can either dry up or the level can drop to the point where sewer gas (and its associated smell) enters your property. The quick fix is to simply run all taps and sinks, plus open windows to get rid of the gas currently in the property. It should clear up quickly.

Dead things

In the UK (the location of this question) it is somewhat common for terraced homes to have no insulation in their walls and are instead just an empty cavity. They often also have a simple solid brick wall between neighbouring properties too. This is just because the UK has quite old housing stock and went through various building booms before the 1970's when insulation became mandatory.

So firstly, check the property's energy performance certificate. It'll tell you from a quick free search if there is insulation or not. If there isn't any insulation, that is a separate problem that you certainly should fix and may also qualify for a grant to do so.

Based on what your EPC says, you'll know if you have an empty cavity or not. An empty cavity can simply be home to animals (and in this case, potentially dead ones). Given the smell is seemingly being carried by the walls in this case, this is a somewhat likely scenario (and also fortunately a pretty easy fix, which will also sort itself out eventually anyway).

Dead things (with wings)

Chimneys are supposed to have a little cap on them to prevent "things with wings" from falling in there, however a house that has been left standing on its own for a while may have had that cap blown off or simply never had one fitted. If the smell is apparent around old fireplace locations, it may be that there is a pile of rotting things in the fireplace and the root cause of the problem is that the chimney needs to be capped.

Mould and damp

In typical draughty UK homes, good ventilation is critical to avoiding mould. A house that has been all closed up for a long time has inherently poor ventilation - their saving grace is that the heating is off resulting in dry air in the house (and thus, no damp). However, this is less true for a terraced property as it'll be taking in heat and moisture from the neighbouring property. This is especially true if there is no insulation in any of the walls, including the party wall. This can result in a build up of mold on external surfaces - namely the inside face of the outer leaf of the cavity and tell tale condensation on the window(s). If this bedroom is located on the party wall of the property then it may be an indication that there is mold growth inside the cavity.

  • 1
    It's not just things with wings that can get in an uncapped chimney. We once had a racoon or possum climb down our chimney (for a long since removed pot-bellied stove) and give birth. Fortunately, the opening to the house had been covered with a piece of sheet-steel duct, then another cover over that. Unfortunately, all the little critters made a huge racket scratching against the metal. After a couple of sleepless nights, I got up on the roof and poked at mom & kids with a chimney sweep brush for a couple of minutes. She moved out that afternoon & I put a cap on the next day.
    – FreeMan
    Apr 7, 2022 at 15:23
  • @FreeMan Ha gosh what a nightmare, those racoons seemingly get everywhere. Certainly brave going up there and poking at it - glad she moved out though! Apr 7, 2022 at 15:25
  • The brave part was the 12:12 pitch roof on a 2-story house. The coon didn't really worry me nearly as much as the potential fall. I was young & invincible, so of course there was no safety equipment.
    – FreeMan
    Apr 7, 2022 at 15:27
  • @FreeMan yikes lol, and I guess the chimney itself was also quite high up - they can be deceivingly a lot higher than they look from the ground! Apr 7, 2022 at 15:29

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