Bathroom Damp Patch

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Hello everyone,

I’m having a bit of trouble with our bathroom renovation. We have a damp patch on the newly plaster wall which is on the corner of an chimney and an outside wall. We initially thought it might be from chimney but we had an expert round (Which trader well reviewed) and he said it’s very unlikely to be coming from the chimney but more likely the roof/flashings. We had a brand new roof last year so the guys came back and say there wasn’t anything wrong with the roof.

I’m not at a loss as to what is causing it. Some key facts:

- chimney is removed below/blocked
- 1930s house
- damp patch is constant even without rain and does really change

Any idea of cause or type of expert to get to look at it?

thanks
 

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KartridgeKid, good evening.

Odd question? is the dark stain actually damp?? suggest you fully tape a bit of plastic over some of the area and insert a tissue paper, see what happens in a days time?

Must admit, faced with the stain in that position instant thought would be a chimney flashing / poor - failed chimney head mortar - rain penetration if there is no vented cap on the chimney pot?

Ken.
 
It doesn’t actually feel wet but I just assumed the fact that it’s never changed colour after fresh plaster was applied that it was caused by moisture. I’ll test with tissue paper. What are you thinking?

I know what you mean about flashing being an issue. But the rain has zero effect on it.
 
KartridgeKid, good evening, again.

Odd one, given there is no increase or decrease because of either rain or summer / winter?

Could be [an outside possibility] that the "stain" seen has been caused by residue coming out of the chimney, the residue is the product of combustion deposits and has an odour like tar?

The residue is a dark, dark brown colour and can and does destroy [over time] lime mortar inside the old chimney flue, this residue can and does "migrate" through the brick work of the chimney to [at times] cause staining to the plaster inside the room.

The staining may??? be being occasioned by the above???

Ken.
 
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It’s a tough one. The plaster is brand new so I can’t see residue staining so quickly and on areas away from the chimney. Plus it’s not in use either.

we’ve hardly had any rain and the damp patch hasn’t changed in size and possible even go bigger.

Im going to get someone to put a camera down the chimney and see what they can see. This has stumped me and my (pregnant) wife is desperate to finish the bathroom.

Thanks
 
Did the roofers give you photos/video of the chimney stack and the stack flashing and flaunching?
You need photos of all the above.
Can you get access into the roof space above the bathroom?
Yousay the chimney breast on the Ground floor below has been removed? Who removed it?

Some of the damp signs appear to be of long standing.
Is there damp anywhere else in the bathroom?
Was the plastering just a skim?
The metal angle bead (which actually looks like a skim bead thatsused on plasterboard) looks rusty near the top, if so it must be replaced with a suitable plastic bead.
Can you post a pic from the left showing the whole chimney breast, and any alcove on the left?
Can you also post a photo ofthe stackshowing from outside street level looking up at the stack?
 
try force drying it with a heater or blower directly under or at it.
the damp looks more concentrated on the wall rather than ceiling .
plastic beads arent used internally , yours is the correct one.
 
Thanks I did try forcibly drying it. The patch got smaller but then got bigger again.
 
KatridgeKid you said you and your pregnant wife were desperate to finish the bathroom but you have yet to answer any part of my post from monday 22 nov?
 

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