Damp wall advice needed

Discussion in 'Job Talk' started by Ross Worth, Jun 13, 2021.

  1. Ross Worth

    Ross Worth New Member


    I have been dealing with a wall that is suffering from some penetration dampness. The wall was built circa 1910 near Cardiff. The outer skin is brick and the original mortar is a very dark back colour, I'm not sure if it is cement or lime-based.

    The stone window sill above the affected wall had a crack in the centre I patched this thinking it was the source of the water. There were also two hairline cracks in the render beneath the cill and above the affected wall.

    I insulated inside with Celotex plasterboard with a built-in moisture barrier. I am now getting some penetration damp at the very edge of where the board finishes. I have removed the tyrolean and render to expose the bricks. They are in very bad shape and feel a little damp, some of the mortar joints are crumbly to touch.

    My current thinking is, install a Catnic lintel, rebuild the brick courses up to the cill, and then install a new cill. Before rendering and repairing the tyrolean.

    I'm wondering if the hairline cracks in the render of circa 1mm and the poor brickwork are enough to have caused this amount of moisture or if something else must be going on.
    Last edited: Jun 13, 2021
  2. Ceebee

    Ceebee Active Member

    It’s a strong possibility that rainwater has been running off the front of the cill and given the lack of a drip groove underneath it’s been tracking back to the wall and getting behind the render once behind it’s trapped and only place it can go and that’s through to the inside add frost damage and it can cause no end of problems. Cutting a drip groove with an angle grinder would have been my first attempt at remedying it, was the render blown? Mortar is black ash btw.
    Is it a cavity wall and is the damp over/around the doorway below?
    koolpc likes this.
  3. Jord86

    Jord86 Screwfix Select

    Before you go causing more damage, check the guttering and post a couple more photos of the exterior. How did you ascertain that the damp inside was penetrating?
  4. Ross Worth

    Ross Worth New Member

    Thanks so much for your reply, it is really appreciated. I agree that the lack of drip channel on the cill is probably where the issue started. I didn't notice that until after I'd removed the render. The render below had cracked but wasn't completely blown, I though best to remove as wanted to replace the cracked cill and make sure the bricks below were solid enough so the new cill didn't crack again. The masonry above the doors is incredibly loose, do you think it is worth installing a catnic or just sort the cill (and drip channel) then re-render/tyrolean?

    The damp isn't directly under above the doors or beside them now, but it used to be before the insulated boards were installed. Now the damp is where the insulated boards stop and a masonry interior wall starts (inline with the left of the removed render in the image). I guess the vapour barrier is just forcing the damp further out to find an escape route.
  5. Ross Worth

    Ross Worth New Member

    Hi Jord, there is no guttering above this section of wall as it is a gable end. I ascertained it was penetrating damp as it changes in relation to rainfall, and not condensation levels inside the room, there is no condensation inside windows and the room is well ventilated and comfortably above due point. There is nothing else to see in terms of photos just uncracked Tyrolean finish to the roofline. There is a box gutter off to the right but that has been checked and the damp is on the left (furthest point from box guttering).
  6. koolpc

    koolpc Screwfix Select

    I guess if the window sill was cracked right through for many years, a lot of water would have been seeping through over time, causing damage.
  7. Jord86

    Jord86 Screwfix Select

    Fair enough, what's the state of the silicone sealant around the windows like? Your house is built with lime based black ash mortar between the bricks, and covered with cement based Tyrolese outside as you say. How long have you noticed the damp coming through?
  8. Ross Worth

    Ross Worth New Member

    The damp has been there in winter since I moved in tow years ago. The vendor had refinished the bottom of the walls around the doors to hide it before I purchased, but inevitably the damp returned.

    The silicone around the doors was bad, and the window sill cracked. I replaced the silicone (window and doors) and sealed the crack in the sill as my first step about 6 months ago. At that time I hadn't noticed the lack of drip channel on the window cill and there were also some cracks to the render below the cill.
  9. Ceebee

    Ceebee Active Member

    I've had a similar issue with a 1930's property but having a cavity wall it was a case of adding the groove to the cills and installing cavity trays and replacing the soldier bricks courses above openings with concrete lintels, I guess the walls dried eventually through ventilating the cavity. I'm not sure what the best approach is now. If you think the wall is unsafe then a replacement lintel & cill needs consideration.

    Your added issue is how do you dry the wall now it's insulated and sealed on the inside?

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