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Old Stone House Renovation - Damp

  • 19-06-2022 6:17pm
    Registered Users Posts: 6


    I have started to renovate an old stone built house and have experienced damp and humid air in the bedroom.

    I have a dehumidifier in the bedroom and it can collect a lot of water.

    I have attached a rough drawing to help explain the layout.

    The bedroom has an unused fireplace that have been blocked, but only with a timber box and fake fireplace. And we have no cowl on the top of the flue, yet.

    The front facing wall has two windows and this wall is plastered. The two other walls are dry lined with stud wall.

    The forth wall has a fireplace/chimney, both alcove walls have insulated board with foil and the chimney walls have only plaster board.

    The front external wall is pebble dashed.

    There is a shed attached to the house, on the fireplace wall. Therefore the fireplace wall is not exposed to the elements but the shed it not airtight, and has an open doorway and window.

    The red arrows indicated yellowing and damp areas.

    1. I was planning on removing the pebble dash this summer and repointing with lime mortar. But would this cause more damp/condensation problems to the bedroom? Would the bedroom interior wall also required a lime plaster to allow both sides of the wall to breath?
    2. Would removing the pebble dash and replacing with a cement sand pointing be a better option so both sides of the wall are non permeable?
    3. Would insulating the fireplace wall in the shed help prevent damp/condensation?
    4. should I remove the insulated foil board and replace with lime plaster?
    5. Could I fill the chimney with concrete or limecrete to prevent damp?

    appreciate any help to answer any of those questions


  • Registered Users Posts: 1,490 ✭✭✭hesker

    Do you know where the damp is coming from.

    A friend of mine had damp problems with an old stone cottage. The ground around it could get quite wet in heavy rain. He fitted French drains in the problem areas and it has virtually eliminated the damp problem.

  • Registered Users Posts: 6 ChrisC6

    hey hesker,

    thanks for the reply, and fair point about the drainage. This house is on a slope and rain water doesn't really pool around the house. I am planning on landscaping the front of the house to level the ground so I will be putting in drainage.

    The damp is in the bedroom, paint is flaking of the front facing bedroom wall with the windows and i did notice mould appearing. As soon as Spring came the dehumidifier was going non-stop and collecting a lot of water.

    unless there is humid air coming if around the fake fireplace? making the room humid and causing the damp on the walls? I was suggesting that we pour concrete down the chimney to see if that helps but it could be risky considering the weight and I'm not sure what state the chimney flues are in.

    the pebble dash looks to be in good condition, I would need to investigate for any cracks, maybe water is getting in somewhere there and cant escape causing the internal walls to be cold and damp.

  • Registered Users Posts: 31,008 ✭✭✭✭Lumen

    Fit a chimney cowl, inspect the chimney stack (safely) and buy a hygrometer or two.

    You need to figure out whether it's penetrating damp and/or condensation.

    Don't go pouring anything down the chimney.

  • Registered Users Posts: 757 ✭✭✭C. Eastwood


    To stop the Dampness, you must first of all ascertain what is causing the dampness.

    It could be caused by 1 or more or all of the following:-

    1. Rising dampness evaporating from the floor
    2. Rising dampness in the Stone Walls
    3. Ingress of rainwater through the walls
    4. Condensation caused by the occupants
    5. Ingress of Rainwater from the roof
    6. Ingress of Rainwater down through the Chimney Cap / flaunting / pots on top of the chimney shaft.
    7. Ingress of Rainwater through the sides and / or the flashings of the chimney shaft above the roof.
    8. Etc

    You need to retrain a Construction Professional with Moisture Meters, Hygrometer and other equipment to diagnose the cause/s of the dampness.

    They will also prescribe what remedial action is required to stop the dampness.

  • Registered Users Posts: 867 ✭✭✭bemak

    It can be hard to pinpoint the cause as already outlined by other posters. I would implement a series of solutions starting with the most straightforward - so for instance - the french drain is a great solution and not invasive internally. Installing one isn't going to be money wasted even if it's not the cause of the problem - it will definitely be an improvement on the situation.

    Having good rainwater goods is another one - making sure water isn't coming in from above - worth checking the roofing membrane, flashings at eaves etc.

    Then you could start to look at ensuring the room is properly ventilated. Ideally you would put in a wall vent but failing that you might get trickle vents in the windows.

    If the problem still persists, you are looking at more invasive works. You could then look at removing the internal render, try to dry out the walls through space heating and then applying a lime render. You could even go down the route of lining the walls internally with hemp before rendering with lime which will improve the u-value while allowing the walls to breathe. In theory this should enable the walls to dry out to the inside but it might take a bit of time.

    If it works out though you could keep the render on the outside and maybe even seal it with something like 'impervo' which can be painted over. In an ideal world you would lime render the outside as well to allow the wall to breathe fully but these kinds of works can get very expensive so unless you have a bottomless budget, leaving the exterior works to the very end after you've exhausted all other options is ok.

    I am in a similar situation as yourself. Posted about it before on here and in the end I'm going down the route outlined above.

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  • Registered Users Posts: 2,569 ✭✭✭Yellow_Fern

    can you post pics of the flaking paint? Is the plaster flaking too? Sometimes a breathable paint on regular skim is enough to let the wall breath, although lime is better, but if it is near a window, there could be a window detailing issue, like cracked cement render. The above post is an excellent way to approach it. Start with the basics like French drains and gutters.