Awful smell coming from loft

[Ian]

I've just been painting the top floor landing, and came to remove the loft hatch. I only open this every few years, as there's so little room up there (only 0.8m height and minimal space with a big beam running down the middle). Last time I opened it years ago, I remember there was an awful smell up there, but didn't pay too much attention to it as I figured it was just musty. However, this time, I took the loft hatch down for a few hours to get it painted. OH BOY, what a stench!

It smells AWFUL. I don't even know how to describe the smell - like stinky feet and something sweet mixed together. Not great.

It doesn't smell like something died, and I can't see any sign of mould up there. The house is about 15 years old. However, there are a reasonable number of dead flies up there, scattered around the spotlights for the rooms below. I can't see any cluster flies active, but perhaps they're outside or hibernating.

Any thoughts on what this could be, or where I can start looking for the problem? There's no enough room to crawl around up there, but I can get up on a ladder and shine a torch around. I can't see anything out of the ordinary. I'm tempted to put some cluster fly smoke bombs up there and see if that has an effect.

 

[Camallison]

Are you sure something hasn't died up there? In our previous house, squirrels and rats were in and out of the loft until I blocked up their entrance/exit. I should have checked first because about 3 months later I went up to get the Xmas tree. Yep, I must have locked in a squirrel. Sweaty socks and an overall sweet smell - classic rotting cadaver smell. Once I had removed it and put a freshener up there, it took a few weeks to smell better.

 

[He who knows]

It does sound so much like it's a rotting corpse.

But I fear more than one. I think we can assume that if it was something large, like your first wife, you wouldn't be asking about it, so that only leaves our small domestic rodents. Whilst I have no expertise in decomposition, if you noticed the smell a few years ago, I'd be surprised if anything which was there then would be anything more than a dessicated odorless husk by now.

 

[KenGMac]

What is the chance of a soil vent pipe from the drainage system dumping foul air into the loft space? Suppose the Soil vent pipe was not taken out through the roof?

Or if there is an "Air Admittance valve" sited in the loft that has failed?

Ken.

 

[He who knows]

Now there's a thought....

 

[Ian]

Thank you for all the replies - I can see the soil pipe vents out through the roof, so I think that can be checked off the list as it appears OK from what I can see (thankfully this is about the only area of the loft I can get access to).

I couldn't see any dead animals up there, but there is a definite sweet tinge to the smell - so perhaps something got in and died among the insulation and I just can't see it. I'm going to get changed in to some overalls this afternoon and have an explore a bit further, just to lift some of the insulation and see if it gives any clues.

Interestingly, the smell isn't as bad this morning up there - although it's been very windy outside, so perhaps it's just been given a bit of a draft if there is a way in.

 

[KenGMac]

A couple of things.

1/. OK the Soil vent is protruding through the roof, that does not mean that there is some sort of a break / crack / hole of some sort in it within the loft? worth a good look?

2/. Roof voids are supposed to be well vented with eaves vents all around the perimeter, this to assist in preventing condensation build up would be worth a check to verify that there is indeed venting and that it is not blocked of by insulation?

Ken.

 

[Ian]

The soil vent does look ok without any cracks or holes - it's about the only area of the loft I can access so I'm happy this bit is ok (at least as far as I can tell).

I lifted the insulation and couldn't see any dead animals, although I couldn't reach a handful of parts of the loft near the back due to the low height and difficult access. However there were a lot of dead cluster flies. I'm going to use a smoke fly killer and see what that does!

 

[KenGMac]

As last post, what does the cross venting look like in the loft?

is there any at all?

Ken.

 

[He who knows]

I'm going to use a smoke fly killer and see what that does!

If there's something rotting up there it will kill the flies whose maggots are living in it.

 

[Ian]

These are the flies I'm wondering about: https://www.xterminate.co.uk/how-do-i-get-rid-of-cluster-flies - I note that they might return year upon year if so .

Cluster flies also cause a rancid, sickly-sweet smell that comes from their saliva. This smell can easily spread to other areas of your home, so make sure to check your attic for flies if you notice an unusual smell in your home. This smell is unpleasant enough on its own, but it also attracts other pests like flies and rats.

This smell comes from a pheromone in the flies’ saliva, and it’s the main reason behind their most annoying habit; they come back every single year!

 

[He who knows]

Looks like you might have found the problem and solution. Might be be next year before you're rid of them?

 

[Ian]

I've got a pack of 4 smoke bombs, so will space them out over the next 12 months and hopefully that'll stop them. I'll report back in a few months and check on the smell then.

 

[KenGMac]

Sorry to bank on about it but?

A roof void / loft should have a cross flow of air. meaning designed / intended vents on each side of the roof, generally in the soffits.

If not then condensation can / will probably build up and wood rot will follow.

If you had a cross flow then a lot of the smells would have been blown away??

Ken.

 

[Ian]

There are definitely vents in the soffits on either side (I've just taken a photo and attached) and there's no mould or condensation up there, buy I will get my "grabber" tool up there to see if I can reach the far ends if possible. It's not boarded up there and height is minimal as the 3rd floor takes up much of the loft height (by design, not added at later date), so very little crawl space. The windy day a few days ago did seem to air the smell out, but I let a smoke bomb off just in case last night.