Damp area on chimney breast - trying to diagnose

[duotwr]

Hi

we've been in our house about 2 years now, it's a late Victorian mid-terrace. In the back room there is a patch of damp - quite distinct - that has been there (pretty sure) since we moved in. Wasn't noticed at first but when I came to strip the wallpaper I found an area that felt damp (and a bit sticky from wallpaper paste).

I wondered about water entering the chimney - but the patch has not changed in size/colour at all over the summer even during dry periods.

I removed the skirting (not rotten or anything) and lifted carpet - but these are all in good nick, no sign of damage from damp.

I noticed that the damp area has some morta/concrete/plaster slapped on the area just below it - down to the floor. I'm wondering if there is some kind of damp course in the chimney breast - but this mortar has bridged it.

The whole area is less than 60cm high, and the same wide. I've attached some photos. Anybody any suggestions what's going on here?

thanks
Keith

 

[Mr Chibs]

Hello

Is the wall with the chimney on, an outside wall?

If if is, are there any tell-tale signs on the outside? ground too high etc
If it's a shared wall does your neighbour have any damp on their side?

At a guess, they large mortar area could go below the DPC or be in contact (bridging) with damp from the ground.

It could also be rain water collecting from open chimney, is the left hand side of the chimney breast dry?

Chibs

 

[duotwr]

Hi

Thanks for replying. This is the party wall, and next door doesn't report any damp. Also no damp on the other side of the chimney breast.

I'm going to take of the mortar at the bottom and also investigate how far up it goes.

One question. Does the damp plaster all need to come off? If i get rid of the bridge then will the area above dry out? It doesn't appear to be blown at all.

Thanks
Keith

 

[Mr Chibs]

I should dry over time, but you'll probably have to remove some of it, depending on when you remove the big mortar lump.

Are the bricks dry on the inside of the fireplace next to the 'damp patch'?

 

[duotwr]

Hi
I can't get access to the inside of the fireplace to check it out. I'm going to have a go at removing the mortar today and see what i find. I'll feed back.

K

 

[duotwr]

Well for anyone interested

I bought a £50 sds drill from screwfix and took the mortar off. Took less than half an hour. The brickwork behind looks fine and the damp plaster above seems pretty sound. I reckon the previous workman might have plastered that mortar on solely to give them something to stick the skirting to.

So l'll give it a week and see if the damp plaster dries out. Here's hoping.

Thanks for replies.

Keith