Chimney Breast Damp - confused!

Discussion in 'Builders' Talk' started by Jasdip Gill, Nov 20, 2020.

  1. Jasdip Gill

    Jasdip Gill New Member

    Hi everyone, been reading lots of chats but still confused, hoping you guys can help!

    There is damp on a bedroom wall covering a chimney breast. Damp is in patches from floor to ceiling, but only on that wall. Damp gets worse with rain, then slowly starts to dry. Had no problems the last few years since I bought the flat.

    It's fully sealed, the chimney does not continue into the loft, it must have been removed during a previous partial loft conversion. Loft is completely dry. It is possible that bricks are at the bottom of the chimney.

    Below the bedroom is the ground floor flat, no damp problems there.

    Chimney breast is on an external wall, pointing seems fine, roofers have not noticed any potential cracks or holes for water. External bricks are damp though suggesting penetrating damp. Gutters seem fine.

    I've had a few damp investigators visit who all suggest replastering with a membrane. In my mind this doesn't seem to get to the root cause of the problem tho. My questions are:

    1. There is no ventilation of the chimney breast, the damp guys have said this isn't a problem, yet everything I read online suggests it does need ventilation?

    2. If ventilation is required, how should I go about it. Try to open up the chimney in the loft and put in a couple of tile vents on the roof (I can't actually find the top of the chimney breast even after lifting the insulation, so may need to bring someone in to look)? Insert a vent (and air brick?) in the bedroom? Install an external air brick / vent?

    3. Should I waterproof the external wall, or will this make the problem worse by trapping in more moisture (even though it prevents more water from entering)?

    4. Should look at both options 2 & 3?

    5. What steps should I take, it may be a process of elimination so I guess simplest options first in the hope it resolves the issue?

    Any thoughts and questions welcome, thanks in advance for your help!

    Photos attached.

    Attached Files:

  2. Astramax

    Astramax Super Member

    What's the extension butting up to the exterior of the chimney breast.
  3. Jord86

    Jord86 Screwfix Select

    Daft as it sounds, check there is a stop end on the gutter outlet butting the wall. If the damp gets worse with rain, then common sense would dictate that it's an external issue. I would check the pointing and brickwork properly as there's at least one spalled brick visible and some replacements done over the years, plus I would also check the external cornice as that would be a prime area for water to soak into and seep in if in poor state.
  4. Jasdip Gill

    Jasdip Gill New Member

    Hi everyone, very sorry for the late reply, unfortunately had an unexpected family issue.

    Appreciate the replies, here's an update on the problem.

    The extension in the photo (which I assume is what you're referring too, please correct me if I'm wrong) is the stairs that lead up to the flat upstairs (my flat).

    The damp seed to improve during the last couple of weeks without any rain, but has now worsened as the rain started again. It has also moved further down, closer to the skirting board.

    I have since had two more people come to look, a damp specialist and a surveyor. The surveyor advised that the pointing is in good condition and the best step to take is to waterproof seal the external wall. The damp specialist advised that we should replastering inside with a waterproof membrane.

    Is there a way to tell if it's penetrating damp from the outside, or hygroscopic salts? Do salt stains appear in a certain 'way', such as from the top down, or bottom up?

    Due to the fact it fluctuates slightly with the rain I would assume (maybe wrongly!) that it's penetrating.

    The building is 20 years old.

    Any thoughts or questions are very much appreciated! I will be able to respond promptly going forward, apologies again for the late response.
  5. Jord86

    Jord86 Screwfix Select

    You shouldn't need to do either of those suggestions being as the building (and every other) was constructed in a manner to repel damp not allow it to permeate and manifest. 'Damp specialists' are usually anything but. Check the cowl on top of the chimney, and stick your head up in the loft to see if the breast is showing any signs of damp up there. It's difficult to believe the building is only twenty years old, it looks far older.
  6. Jasdip Gill

    Jasdip Gill New Member

    Apologies, the building is much older, I thought the same and realised I read the wrong paperwork! It was converted to flats 20 years ago. The building itself is much older.

    There is no chimney in the loft, it has been taken out and does not go to the roof. I've looked in the loft and there is no damp anywhere and no leak thru the roof.

    Thanks for your reply, please let me know if you have any other thoughts or questions :)
  7. Joshuaojs

    Joshuaojs Active Member

    Is the chimney breast rendered in sand and cement
  8. Bob Rathbone

    Bob Rathbone Screwfix Select

    It seems that damp is condensing inside the chimney void, it may be possible to install an air brick outside at the bottom of the stack, at your floor level, and if the chimney has been sealed at the roof, install another air brick at the top. This will ventilate the void in the chimney with cold but dry air. It will take around 6 months but the damp should be solved.
  9. The Happy Builder

    The Happy Builder Screwfix Select

    Rule of thumb, if there is black mould it's condensation as the water is pure, if there is not any black mould chances are it is penetration as the water has picked up salts on its way through the way, so black mould won't develop.

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