Small damp corner of carpet

stuart45

It's possible that the cavity wasn't cut out properly 0n the old wall when the extension was added so that it continued along the wall.
You can see that there is a header just below the DPC where the extension starts, which could allow moisture to track back along it.
When you add n extension to a cavity wall you should either cut out a cavity width of brickwork, or BC will allow a slot right though the brickwork and a vertical DPC slotted in.
Should be cut out like this.
phpetvds9pm-jpg.46284 (760×570) (contractortalk.com)

ryan7

I'd say it's condensation. Your bookcase is reducing the amount of airflow in that area so the moisture stays were it is. 
You need to ventilate that area. 

stuart45

ryan7 said:

I'd say it's condensation. Your bookcase is reducing the amount of airflow in that area so the moisture stays were it is. 
You need to ventilate that area. 

Good point, condensation is also a likely suspect.
If penetrating damp is adding to the problem, or coursing it, the header at the base could be a problem.

Smithy99

Okay thank you. We do get condensation over the winter and use a dehumidifier in that room.  I'm going to give the corner a good hoover later as there was lots of dust/debris under the carpet. Hopefully I'll be able to feel the actual floor properly and see if that feels damp and see if it all dries out whilst the furniture has been moved (although it's dry here atm as in no rain so would it dry out anyway?) 

How do we know if it's a header problem? Or fix it? 

stuart45

Smithy99 said:

How do we know if it's a header problem? Or fix it? 

I am only guessing, as this does sometimes cause damp issues with extensions in that corner. You need to put your camera in the cavity to see what is there. If you look at the diagram the top left is a plan of how the house was pre extension.
below is how the walls should be. To the right the external wall which is now an internal partition wall is now in contact with the external skin and a potential damp risk. and built incorrectly.
If it's just the header and the cavity has been cut out, then just remove it and replace with a half bat.

Smithy99

Okay that makes sense thank you very much

koalakoala

Does condensation cause slugs to come in ?  yuk

Smithy99

 I've filled the gap with some caulk which will hopefully mean it's no longer as cold in that corner and left a bigger gap where the furniture is and will keep an eye on it.

im still a bit worried about the pipe though!