Water stain appearing again on new plaster

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  • Laura Francheteau's Avatar
    Level 1
    Hello, we had water penetrating through our bedroom walls for the last 4 years. As it is where the roof and chimney meet, we’ve been told it was an issue with the lead work which was changed twice. The second time was 5 weeks ago, we waited for 4 weeks for the wall to dry and had the room replastered a week ago (after the old mouldy plaster was taken off). Unfortunately, the plaster near the chimney only dried in a few places, and now the stains we were struggling with are reappearing again. We have no idea why this is still an issue and how to fix it. The strangest thing is that the stains only appear during the night. We wake up in the morning to a wet wall, leaving the windows open and using a dehumidifier help dry the majority of the stains but not all of it completely and anyway it reappears the following morning. Any suggestions on what the issue could be? Many thanks for your help.

    Photo 1 is what the wall looks like in the morning
    Photo 2: the same wall after a full day of window opened and dehumidifier on
    Photo 3&4 are whilst the platerer was taking off the old plaster
    Photo 5 was the problematic wall before the lead work and new plaster
    Attached Images Attached Images      
  • 6 Replies

  • Best Answer

    Ajw's Avatar
    Level 14
    Best Answer
    Good morning
    check your sealant around window sill sometimes it can be damaged check underneath window sill for missing pointing work which would allow water ingress
    on your other damp issue
    any broken tiles leaking gutter joints
    if chimney area have you had chimney capped off
    two things come to mind
    water ingress for four years can lead to saturated brickwork with no ventilation due to no air flow
    has your window got small vent fitted
    to allow constant air flow may possibly be heating on window closed night time condensation
    hope this sheds some light
    also check your flaunching on top of chimney stack if cracked may allow water through and your chimney will need air bricks or suitable chimney pot vent
  • Best Answer

    Sean's Avatar
    Level 20
    Best Answer
    https://www.directstoves.com/resources/common-causes-of-damp-in-your-chimney-what-to-do-about-them/amp/

    hi Laura, you might find the link of interest.
    ​​​​​​​regards sean saunders.
    SEAN SAUNDERS DECORATING
  • Ajw's Avatar
    Level 14
    Also just check loft insulation is not over wall plate and soffit internally as this can restrict air flow
  • Laura Francheteau's Avatar
    Level 1
    @Ajw thank you very much for your advice. Here are the answers to some of your questions if it helps clarifying what the problem might be?

    • any broken tiles leaking gutter joints - both roofer that did the work said there was no problem on that front
    • if chimney area have you had chimney capped off - yes many years ago and the roofer said there is no cracks on the chimney capp
    • has your window got small vent fitted - no no vent fitted so we are letting the window open overnight
    • also check your flaunching on top of chimney stack if cracked may allow water through and your chimney will need air bricks or suitable chimney pot vent - no cracks mentioned by our roofer and we have air bricks on the chimney
    • check loft insulation is not over wall plate and soffit internally as this can restrict air flow - how could we do that? sorry I don't know what a 'wall plate or soffit' looks like, do you have any photo or explanation? The plaster wall is the only thing we can see, we don't know what's underneath.

      Here are some photos of the roof after the latest work done (replacing lead flashing around chimney stack)Name:  IMG-20211212-WA0007.jpg
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  • Ajw's Avatar
    Level 14
    On top of your brick work in the loft you will have a four by two timber which your roof timbers rest on then the cavity between inner and outer brickwork check if your insulation is over the cavity which will result in restricted airflow make sure your insulation is on the loft side of wall plate not over the cavity to the soffit