Damp carpet question

[Jazcolbrook]

Hi , my lounge carpet is damp to the touch in one corner under the sofa and in patches along the skirting board again behind the sofa , the underside of the carpet is dry as is the underlay and concrete floor , we use a dehumidifier in the winter due to condensation. Any ideas please ?

 

[Mr Chibs]

Internal, external wall?
Double brick construction or cavity wall?
Any plumbing nearby?

 

[Jazcolbrook]

Internal wall , no pluming not sure if cavity or not it’s an inside wall between lounge and dining room

 

[Mr Chibs]

Would imagine it's a single skin wall (is the house old?) could be a breeched/damaged DPC allowing moisture above it.
Could also just be condensation, condensating behind sofa and over time wetting the carpet.

Think you'll need to move the sofa, lift carpet and have a look, if the floor is a suspended wood floor, are the air vents clear?

Are there any signs or ropey paintwork above skirting?

Sorry it's so many questions

Post some photos when/if you can.