Damp patches on internal wall / chimney breast - where to start?

Goldfinch_1997

There are a few things going on and we’re not sure where to start.  

What can we do to track down what the problem is likely to be?
So the chimney has been capped off for some years and we’ve had a look at the chimney. 

It looks ok, as does the flashing.

The patches are on a downstairs wall and below the bathroom….so is that possibly where the problem is coming from?

The walls in the bathroom have those big plastic panels (the ceiling does too) so could be hiding all sorts?

The patches that we’ve spotted are at least 5ft above the floor.
…where do we start?

stuart45

Photos are a good start.

Goldfinch_1997

Here are a couple.  There are no patches in the built in cabinet to the right.  We did have a large picture hanging from the picture rail and it’s only when we moved it most of this became apparent 😢
The wallpaper above the picture rail on the right has come away from the wall slightly too.
 

stuart45

Is the damp where the flue is?

Goldfinch_1997

It’s all filled / plastered in.  The closed off “fireplace” alcove is below the hook on the picture rail so not central to it (sorry there’s a piece of furniture in front of it so can’t provide a photo of it at the moment). Is this damp you think rather than a leak?  I can’t see a vent.  The cowl on top of the chimney is vented.

stuart45

It should be vented at the bottom as well as the top. Hygroscopic salts in flues can also cause damp issues.

Goldfinch_1997

Thanks for that. I can’t see signs of salts.  

If we add a vent will it dry it out?  Or do we need to do more than that?

stuart45

Try a vent first. You can't see hygroscopic salts, as they don't crystalize. 

Goldfinch_1997

stuart45 said:

Try a vent first. You can't see hygroscopic salts, as they don't crystalize. 

Haha…so much for Google 😊

plumb1_2

Can you get into the loft with a torch to check any visible leak. You can’t really check a chimney from ground level. Could be a slipped soaker, hole in the chimney back flashing, cracked slate/ tile.

Goldfinch_1997

It’s tricky.  The loft hatch is on the opposite end of the room (about 3m away) and there might be space to shuffle over on my knees …but with Vermiculite insulation not easy.  I did take a look yesterday but didn’t notice anything.  Is there something that I’d notice at that distance?