Possible damp appearing on wall?

[iainmax]

Hi,
My sister has asked me to have a look at a mark that's appeared on her interior wall. The wall is plastered and has been painted over some time ago. The mark was evident over a year ago and has grown in length over that time. There are also a couple of spot marks on the same wall.

Here's what I know so far:
The house was built in 1998 and has damp-proofing.
The interior wall is on the gable end of her house.
There is no evidence of a leak from the bathroom above.
She has a combi boiler and there are no tanks nor evidence of leakage coming from the loft.
There is no evidence of damage to the brickwork.
The marks are not wet to touch and there is no damp rising anywhere on other parts of the wall.
The roof hasn't been inspected from above.

Here is a picture of the offending mark. Any help in identifying the problem is greatly appreciated. Apologies if i am in the wrong forum and thanks to the mod who might have to move it.

Thanks,
Iain

View media item 71682[/img]

 

[BigIan]

Hmmm the pic looks odd not what I would expect of damp. Is the line a ridge or lump in the plaster or is it just a dark mark? Is there any movement in it when you press on it?

You say "the internal wall is on the gable end". So is this wall internal or external?

As you say this mark has only progressed gradualy over a year and there is a bathroom above I have known minor leaks from failing bath seals and grout to cause damage to plaster and paint work over time.

 

[iainmax]

Sorry for the delay. I asked my sister to have another check to see if there is movement. There isn't any, it's just a dark stain. It is also completely dry.

The wall is internal, but it backs onto the gable end. I wasn't sure if that fact was important or not.

Thanks,
Iain

 

[foxhole]

No sign of bathroomleak, so you had bath panel off?