Damp: Wet patches appearing through painted wall

Discussion in 'Plastering and Rendering' started by Mark Lewis, 2 Nov 2021.

  1. Mark Lewis

    Mark Lewis

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    Hi guys

    This is actually a question on behalf of my mother who lives in a fairly old property, built in 1895.

    She has an internal downstairs wall that seems to have damp water marks showing through the paint. She actually had a "damp specialist" in a couple of years ago as she was having a lot of black mould growth in the corner of the room behind the sofa (the offending wall). We have since realised this black mould is just where the warm air of the room is meeting the cold surface of the wall, condensating and then being permnantly wet at surface level to allow the mold to grow in the moisture. It only seems to happen in this corner of the house though

    The guy ended up hacking off the plaster to the brick up to about 1.5m high, injecting DPC along the wall into the mortar between the bricks and then a sand and cement mix (i think!!) to rejoin the wall with a skim then applied over the top to even it back out again

    What seems to be happening is a damp water mark slowly appears through where the remedial work was joined to the existing/untouched area above 1.5m. We have tried sanding it back to the skim and reapplying all manner of paints but it always comes back to the point where the paint flakes off and shows the pink/brown skim underneath

    Any advice on how to tackle this once and for all? I think we have painted it 5 or so times, each time with a different paint

    The pictures will help to see what I mean
     

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  3. Mark Lewis

    Mark Lewis

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    Note there is an air vent bottom left (why!???). This corner is where the black mould tends to grow. Could it be the vent is allowing colder air to come in, cool the wall in that area and increase condensation?

    My real concern is the wet coming through the paint rather than this black mould in the corner though. She just manages it with a dehumidifier which keeps the air in the room at a lower humidity which stops the mould growth
     
  4. Mark Lewis

    Mark Lewis

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    This is the offending corner from the outside. The house is rendered which then stops at a sort of "skirt" before the brickwork is exposed to floor level

    As its 125 years old I dont think it has a cavity inbetween the brickwork
     

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  5. JohnD

    JohnD

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    stand back please and take a wider pic to show the entire wall, from gutters to ground.

    mark on it where the damp patch is

    and mark where the air vent comes out.

    How thick is the wall?

    is the inside room fully above ground level?

    what is above it?

    Do you know where the water pipes are, and are any in the wall?

    BTW I think the brick plinth is probably a later addition, built to hide something, for example water damage or damp.
     
  6. Mark Lewis

    Mark Lewis

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    I will take a few more photos when I am there later in the week. This is as much as I can get from Googlemaps streetview for now lol!
     

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  8. Mark Lewis

    Mark Lewis

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    The building was actually a school which was later repurposed for housing. I think they managed to make 4 houses out of it in total which is why you can see further back the render colour changes when it switches to a different property
     
  9. Mark Lewis

    Mark Lewis

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    Ive marked with a blue dot where the issue is but appreciate its difficult to see. I will try and get some actual pictures ASAP
     

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  10. JohnD

    JohnD

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    please have a good look at the gutter when you're there, and any signs of a drain in the ground.

    Is there a bathroom above?
     
  11. Mark Lewis

    Mark Lewis

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    I can confirm there isn’t a bathroom above , the bathroom is actually diagonally opposite and upstairs so it couldn’t be further away
     
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