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Crack to roughcast

Discussion in 'Plastering and Rendering' started by Mckenzie1, 17 May 2019.

  1. Mckenzie1

    Mckenzie1

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    Hi all. I have just discovered a couple of cracks to the roughcast on the front of our house. We moved in a year ago so have no idea how long they have been there. The one above the window is the more noticable perhaps a 3 or 4 mm wide. The one below the window is very thin and kind of hard to see.

    Do you think these could be patched somehow or would it require all the roughcast to come off?

    The roughcast doesn't seem to be coming away from the wall as it looks flush from below.

    Thanks for your time.


    [​IMG] [​IMG]
     
  2. KenGMac

    KenGMac

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    Mckenzie1, good evening.

    Notice this is your first post on the board, if no one else does, Welcome.

    OK

    First impressions are all the cracks can be explained as being "Thermal"
    From the top.
    The crack above / right of the upper window.
    This is being caused by differential thermal co-efficient s between the Concrete lintel and the brick / block work of the external wall, this causes cracks on or near the junction between the Concrete lintel end and the surrounding wall.As an aside this is a classic image of such a crack.

    Now for the crack below the upper window right hand side, again "thermal"
    The crack has formed [in general terms] mid way along the length of the external wall between the upper window and the lintel of the rear [Kitchen?] door.

    I have enhanced your lower image but cannot see any cracks in the brickwork ?

    What may?? have happened is that the wall below the roughcast is Block work, and the area below is facing brick [the block work is cheaper than Facing brick.

    One question? are there any cracks internally? the only one I would expect is a hairline crack in the plaster near the external crack at the upper window?

    Ken.
     
  3. Mckenzie1

    Mckenzie1

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    Hi Ken,

    Thanks for getting back to me. There are no internal cracks that I can see (touch wood).
     
  4. KenGMac

    KenGMac

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    Mckenzie1, good evening, again.

    Suggest you consider the following

    Using a very fine bead of CLEAR silicone you CAREFULLY fill the cracks.

    Prior to above, use a dustpan and brush to get some of the roughcast material on the wall.

    Then insert the "bits" of roughcast and push them into the thin bead of Mastic [be quick, Mastic can become hard quite fast]

    The mastic will help prevent rain water ingress, the stuck in bits of roughcast in effect "mask" the visual appearance of any cracks.

    One thing I meant to mention?? from the images posted, it appears that the elevation of your home that is affected gets the full benefit of loads of Sunshine? hence the "Thermal Effects"

    Ken.
     
  5. Mckenzie1

    Mckenzie1

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    Thanks again for your advice. Need to see about getting some ladders. Cheers.
     
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