Chimney Breast Damp with Pictures

[LornaC]

Hi All,

First time poster so apologies for length. Hoping someone can give us some guidance. Back story is we bought a flat within an old house a couple of months ago. Previous owners advised that damp issue was due to a roofer disrupting flashing when they removed a jackdaw nest from one of the chimney pots (they told Surveyor this too). This was fixed over 18 months ago, however, at certain times the wall is still damp. The chimney pot was capped and chicken wire put round it. Seems to dry out and then gets damp again. The fireplace has a board over it but is not attached. We have started to take daily readings noting weather conditions. I have looked on the internet but can't see any images of dampness that has the same pattern. Any help appreciated.

(middle four pots are ours and think the offending one is the one with the soot marks- have I answered by own question here?)

Dog likes to be involved!

 

[d000hg]

If the damp keeps coming and going my guess is this might be unrelated to any external leak/dampness now. Once plaster gets wet once, it can be spoiled and will then suck moisture from the air (hygroscopic salts IIRC). So it might be on damp days or when you run your washing machine, the air in there is damp and highlights the issue. We have patches like that in one bedroom - if we hang up the laundry we get a big stain which vanishes otherwise.

You probably want to find an independent damp specialist to check this. Another option could be to look up inside the fireplace.

 

[LornaC]

Many Thanks for your advice. Might ask the chimney sweep to have a look up when he is here next and speak to a damp specialist once we have collected all our damp meter readings.

 

[bobasd]

the pic shows a fireplace in a room tight to the roof slope - is it an attic? if you have a lot space above the room in the pic, go up an examine the gable wall an internal chimney breast for damp signs.
the pic also shows a chimney stack with soot penetration from the chimney flues.
unless your house is on the right an the neighbours are on the left of the stack then all six terminals/pots are yours? do you have six fireplaces?
all six flues in that stack, need to be swept an the stack an its flaunching an flashings need to be checked - photos of before an after are common for roof work nowadays.

moisture is enterin the stack an runnin down the flue to the attic room at least. could be runnin down other flues as well.
the stain is penetratin damp from the flue.
the plaster on the face of the chimney breast needs nockin off an bein redone with a lime render.
all your flues need through ventilation with at least a vent at the bottom an the top in each flue - terminal caps must allow ventilation.

i dont think it was ever a flashing problem unless it was the top of the stack an the flues an the flashing.

 

[LornaC]

Thanks for all the info. The room is in the attic. It has no void. 2 of the chimneys belong to the basement flat and 4 are ours. No damp readings anywhere else at the moment although there is one behind a false wall and another is covered by wood panelling. 3 out of 4 definitely vented at bottom. Does soot deposits mean it needs repointing? Cheers

 

[bobasd]

the stack has four sides an a top, an dependin on whats found close up its difficult to say if it will need
repointing.
main thing at the moment is to get all six flues swept.
using a smoke bomb or a small fire will show which fireplace feeds which terminal.

whats covered by a false wall an panellin - fireplaces or damp patches?

 

[LornaC]

Ok great thanks. Chimney sweep is due to come out soon. One very small fireplace is completely behind a stud wall and the living room has a wood burner (lined and swept every year) and panelled chimney breast. We would only know if there is dampness behind these things if we removed stud wall and panelling. Cheers