Strange damp problem

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I noticed a bit of a musty smell coming from my daughters bedroom as of late.

Nothing obvious so I pulled out the furniture and found this on the carpet. It was damp to the touch so I’ve cut it out and sprayed it with mould killer. In the process of letting it dry out.

Now - what is it and how did it get there?

It runs the precise length of an IKEA unit and there’s no sign of any other issues anywhere in the room.

In terms of what outside looks like - there’s another picture attached (the white stuff is ant powder and not efflorescence).

I’ve measured where the main spot was in the room to the outside wall and taken a picture of roughly there.

I definitely have a DPC, and it’s definitely not bridged.

It’s a solid concrete floor construction (no DPM under the concrete) with a cavity wall. There are no pipes in the floor at all.
 

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Might it be condensation on the wall? Possibly caused by a lack of airflow behind the unit- where the airflow is restricted.
 
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Might it be condensation on the wall? Possibly caused by a lack of airflow behind the unit- where the airflow is restricted.
Thanks - could be. It’s tracking quite far under the carpet and underlay. It’s quite well ventilated and no issues anywhere else though…
 
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Thanks - could be. It’s tracking quite far under the carpet and underlay. It’s quite well ventilated and no issues anywhere else though…

I have seen that kind of thing before. The moist air from breathing condenses and runs down the wall, and on to the carpet In the areas lacking airflow).

I am not saying that is definitely the cause.

You could try taping some bacofoil to the wall for a few days and see it it is moist first thing in the morning (once you pull the unit back out). Or put some on the floor- taped to the skirting and see if it is wet on the upper surface.
 
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I have seen that kind of thing before. The moist air from breathing condenses and runs down the wall, and on to the carpet In the areas lacking airflow).

I am not saying that is definitely the cause.

You could try taping some bacofoil to the wall for a few days and see it it is moist first thing in the morning (once you pull the unit back out). Or put some on the floor- taped to the skirting and see if it is wet on the upper surface.
Thanks - I’ll give it a go but I doubt I’ll get any condensation at this time of year.

Looking at how bad it is though - it wouldn’t surprise me if it’s been an issue for a long time.

In the winter, windows are literally running with it.
 
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Classic condensation.

The musty smell is mould spores. Mould only grows on fresh water from condensation.

The external damp staining may well be a separate issues cooling the wall to allow internal air to condense.
 
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Classic condensation.

The musty smell is mould spores. Mould only grows on fresh water from condensation.

The external damp staining may well be a separate issues cooling the wall to allow internal air to condense.
Cheers - very helpful.

So in terms of a solution: rip out old carpet, let it dry down thoroughly, re-carpet and remove Ikea cabinet from external wall?
 
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Is the carpet actually damp?

Typically condensation mould on furnishings may not have any detectable damp. And the condensation just reoccurs nightly

You need steralise the mould clean it and determine the cause of the excess humidity being produced (or that external stain) and deal with that.

If you don't deal with the cause, any new carpet or furniture will go the same way.
 
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a damp patch that is the precise area of the shelving unit?

do you mean the carpet was damp where there was something on it?

you find exactly that in a shed or cellar where the concrete floor is damp. the water evaporates off fast enough that you do not see damp patches. But if you put something on the floor, damp forms underneath it because you have prevented evaporation

this is a noted cause of paint tins in sheds rusting through the bottom.

put a sheet of clear plastic on the floor, weighted down, see if moisture forms undrneath it

you say "a solid concrete floor construction (no DPM under the concrete)" which would fit

how old is the house?
 
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1960.

It had Marley tiles with bitumen as a floor covering before I carpeted over it.

Rest of the room is fine so far as I can see. Also - it was tracking from wall / floor junction back into the room…
 
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It seems to be low level condensation - are there any similar signs in the corner?
Typically, trickle heating and trickle ventilation will be very helpful.

Is the bedroom in the main house or an extension?
1960 implies a cavity wall but no CWI.
Pics showing the full damp stained elevation up to eaves might help to show why the elevation is damp stained?

The skirting appears to have been boxed or packed out from the wall?
Is there a any history of previous damp work?
 
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No similar signs anywhere else - but then there’s no other big furniture which sits on the floor on an external wall. It’s part of the main house - it’s a bungalow.

It’s cavity with insulation. No damp anywhere else in the house or any signs of it.

That’s not damp staining on the wall - it’s weathering. The cleaner bit is by the porch which shields that bit of the wall from the worst of the elements.

There’s no trickle in the winter but it’s kept warm. Windows run with condensation in the winter, and I’m fully aware of it. We’re changing windows from metal very old double glazing to UPVC modern glazing shortly.

Skirting is neither boxed nor stacked. It’s attached to a plastered wall which doesn’t bridge the wall / floor junction.

No damp work anywhere but then there’s literally no signs of damp anywhere else in the house?
 
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The bottom of the cavity might be full of damp builders rubble.

Could water be entering round or under a window or doorframe?

When the windows are removed you can look down the cavity, probe it, use a builders vac to suck the insulation fill out for a look. Or remove just the window board.

You can use a metal tube on a builders vac to suck sand, snots, small rubble out of a cavity
 
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Could be - but no issues anywhere else and it seems a massive coincidence that the carpet has only gone bad under the unit?

The window frames are stone mullions, which doesn’t help with condensation but they’re not on the same wall as this issue. The floor underneath the windows is dry and free of problems.

When the windows are removed I have no need to remove the interior window sill because there’s no damp or any issues on that wall…
 

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