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hi all this is my first post .im doing up my 1920s home ,taking forever ive got a damp spot in the bedroom where the chimney is,ive looked over the roof had the lead flashing replaced,and the damp is still there,ive put on a cowl thats not helped,forgot to say we still use the chimney with a flue any help would be great thanks

ant67 wrote:hi all this is my first post .im doing up my 1920s home ,taking forever ive got a damp spot in the bedroom where the chimney is,ive looked over the roof had the lead flashing replaced,and the damp is still there,ive put on a cowl thats not helped,forgot to say we still use the chimney with a flue any help would be great thanks

sorry should say use the chimney with a liner

What sort of liner and fire.

i think its a stainless steel flue ,i use a wood burner stove

Sounds like the wood may be to green, and the flue may be holed.

The plaster on chimneys often contains hygroscopic salts which attract condensation at a R/H as low as 50%. This problem often confuses the roofers who think that it is a leak. You can have the plaster tested for these salts. If it contains them replaster with sand/cement/salt retarder.

how can i find out if there is a hole ,the wood i use is always dry .never green i make sure of that

stuart45 wrote:The plaster on chimneys often contains hygroscopic salts which attract condensation at a R/H as low as 50%. This problem often confuses the roofers who think that it is a leak. You can have the plaster tested for these salts. If it contains them replaster with sand/cement/salt retarder.

thats why i had the roof sorted and the lead flashing done,can you get a diy kit for this ,if it is this ,is there anyway of fixing the problem

Can you post a pic showing the damp, if the flashing was leaking it would take a while to dry out, you may see signs of it in the loft.

You could smkoke test the flue but that would mean taking the benching off, or you could get a camera stuck up it.

I would go with the flashing for starters.

The salts are produced from the burning of fossil fuels and deposited on the sides of the flue. These fuels also burn hydrogen which combines with oxygen to produce water vapour. As the vapour gets higher up the flue it condenses and soaks in the flue and takes the salts though to the face of the plaster.
This was done before your chimney was lined, and so now once any leaks from above are sorted, re-plastering will sort it if salts are in the plaster. I don't know of a DIY testing kit, but there may be.
IIRC they are Nitrates and clorides. Think how easily Sodium Cloride soaks up the moisture in a dry room.

cant get any pics at the mo ,,im going to look down the chimney with a light to see if there are any holes down there ,all the work on top have been done roof ,flashing,no water damage in the loft.it does seen to be more damp when its cold and damp outside,i live right by the thames.i have a cowl on top but it does get very windy here as there are no houses between me and the water,there has been a garage built so the bottom of the chimney is now inside ,i dont know if you need air vents at the bottom,im a baker by trade the chap that i got the home from told me the vent at the bottom that he put in was ok,even as its now on the inside, i know why the bedroom had been repainted now,thanks for your help so far