More Damp Chimney Breasts..

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parkview094
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Location: Hersham, Surrey
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More Damp Chimney Breasts..

Post by parkview094 » Sat 5th Dec, 2020 10:46 am

Apologies as I realise this is an old topic, but I'm really struggling with what to do about the classic problem of damp on a chimney breast.

Here's a picture of what's going on..https://drive.google.com/file/d/1ZCNZRk ... sp=sharing

There is mid-level and low-level damp on the wall made all the more obvious as I've removed the wallpaper.
This is an internal wall and on the other side is whats left of the chimney breast in kitchen. The Black marker pen indicates the position of the brickwork on the other side.
Immediately on the other side (in the former chimney breast location) is hob and units underneath.

I've had a look behind the units in the kitchen and there is no sign of damp on the kitchen side of the wall.
The house is 3 storeys and the chimney extends a full further story above the top floor. There is no sign of damp on any of the other parts of the chimney breast further up in the house.
There used to be a floor-standing boiler where the kitchen hob is now, and so consequently this particular flue is lined. When I installed the hob, I installed an extractor hob above in the former chimney void, but that vents out through the rear wall.

I did install small air vents around the extractor above the hob.

Here's a picture on the top of the chimney stack showing the top of the liner..

https://drive.google.com/file/d/1Z4uo96 ... sp=sharing

It seems as though there must have been a historic low-level damp problem in this area before as the previous owner has replaced both the floor joists and floorboards in this area.
Looking under the floor void now, all seems nice and dry though with no weird smells or obvious signs of damp.
Also - there doesn't appear to be any deterioration to the skirting board.
Walls are still on their original lime paster.

Any thoughts as to...

1. Why there might be high-level damp in that spot only, but nowhere else on the stack?
2. What the best way to address the low-level damp would be?
3. Would it be worth my removing the old flue liner do you think? It's currently just coiled up at the bottom of the flue. (I did wonder if water was running down the liner and collecting and the bottom, but I'm surprised there's no sign of damp on the other side of the wall?)

TheForge
Posts: 304
Joined: Tue 25th Jan, 2011 4:37 pm
Location: Somerset

Re: More Damp Chimney Breasts..

Post by TheForge » Sat 5th Dec, 2020 10:21 pm

As the sub floor is dry I suspect this is salt migration causing the staining and leaching from the sooty deposits inside the chimney. Why it is only apparent in these patch is not possible to tell. Perhaps voids in the wall at these points?

parkview094
Posts: 139
Joined: Wed 22nd May, 2013 9:53 am
Location: Hersham, Surrey
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Re: More Damp Chimney Breasts..

Post by parkview094 » Sun 6th Dec, 2020 10:20 pm

Removed the wallpaper and some of the plaster. Had a spot of luck..
IMG_20201206_134209.jpg
IMG_20201206_134209.jpg (226.65 KiB) Viewed 384 times
Seems there was a random piece of wood sticking through the wall where the high-level staining was. The wood poked right through the wall and was touching the metal flu liner on the other side. The wood it's self was completely rotten, so I suspect this was wicking moisture through..

The middle level staining remains a bit of a mystery. Brickwork behind the plaster looks absolutely bone dry.

Similarly, the low level damp - brickwork behind and below all looks dry. Chemical / Salt deposits mayyyybe? Struggling slightly to find a consensus as to how best to deal with these.. Is neutraliser just a gimmick?

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