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using a mesh to repair a vertical crack in internal brick wall

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  1. #1
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    Default using a mesh to repair a vertical crack in internal brick wall

    Hello,
    My Neighbours have asked me to help fix a vertical crack in one of their internal walls
    it's a brick internal wall, the crack extends from top to bottom and is up to about 5mm wide.
    They got an engineer to look at the crack and i am satisfied with how to patch it up according to the engineer report save for one bit.
    The report has a small diagram that shows the crack filled in with new mortar which is fine but then some sort of mesh nailed to each side of the crack. the mesh ends up being covered by render and plaster obviously so it is completely hidden
    I assume the mesh is simply a reinforcing method around the crack, but what sort of mesh is used, is it rigid or something like flywire from bunnings (which I assume would only then act as an adhesive for the render to the face of the brick rather than a structural support to the brick itself)

    has anyone ever used mesh to repair cracked brick walls and what is it that is used?
    cheers
    Damien

  2. #2
    Senior Member Batpig's Avatar
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    Dear Damien,

    Is the crack by any chance right in at an internal corner? (ie. the inside-corner of where two walls meet?...)

    If it is, perhaps you could use a plasterer's "Corner Bead"...
    They're like a long length of perforated thin-guage metal Angle (although you can also get plastic versions) that are used to reinforce the corners of cement-rendered walls. The legs are only about 50mm wide or so, though (Has the engineer nominated any sort of required leg-length?...)

    Anyway, last time I noticed about 6 months ago, Bunnings had the metal ones in that last row that is right-up-hard against the wall along the Timber-Yard. Only thing is - I think they've had a bit of a rearrangement since then. Perhaps if you ring them, and ask to be put through to "Builder's Hardware", they might be able to tell you if they still carry them, and what the Leg-lengths are.

    Best Wishes,
    Batpig.

  3. #3
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    Well from my experience, my house has alot of moment with all brick internal walls. When I bought the place, every wall had cracks generally above doors or windows. I had a heritage solid plaster re-render and set all the walls, he used a style of flexible (plastic?) mesh over all areas which were cracked.

  4. #4
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    although internally, the crack is on a flat part of the wall, there is a 90 degree corner on the external brick wall.
    the adjacent room has a wardrobe in the way so i can't tell if there is an equivalent crack to the corner in the other room
    the crack snakes up the wall not in a dead vertical line

    if i could draw in ascii format it would look like this:

    ````````````````````external wall
    ```````````````|| =======================||
    ```````````````||```````` room 1``````
    `` ||
    ```````````````|| <----- `````````````
    ```||
    ================|`````
    room with crack```||
    ````````````````| at this internal point ||
    ````````````````|````````````````````````||
    ````room2 ``````|``````````````````````` ||
    ````````````````|``````````````````````` ||
    ````````````````|________________________||
    ````````````````|
    ````````````````|
    ________________|

    edit: fixedsys font my @@@@

  5. #5
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    The stuff you want is plasterers mesh. In Adealide you can get it from Rayners building supplies in Thebarton. If you want to pay more, you can get some small square (10mm) galv trellis mesh from Bunnies. Use some short galv clouts to secure it into the wall. Ive used both in the past, both work. Try to lay the mesh wide over repair if you can, dont try and do the repair in the width of a 50mm bolster (having said that replastering is somewhat simplified if you keep it under the length of a large trowel. If you want to get really carried away, douse the brickwork with Bondall in the places where you are going to repair to help the mortar and render stick.

    Have fun with it

  6. #6
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    fantastic, cheers for that, do you use it over the entire length of the crack or just at a few strategic points along it?
    i cut the old render off for them yesterday and opened up the crack somewhat to get some new mortar in there. i have given myself about 5 to 1o cm either side of the crack to play with so should be enough to work with, and yes i am dousing it all in gripcrete (diggers verion of the bondall brand...i assume them to be much of a muchness) prior to re-mortaring and rendering.

  7. #7
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    Put the mesh down the entire length of the crack. Its basically serving as reo for the render.

  8. #8
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    Hm, interesting information in this thread...a few months ago, I "disappeared" several narrow cracks like this using either "Cornice Cement" or Spackfilla ( I had packets of both), but NO MESH because I didn't know about it, then repainting, which was OK at first ..but now, I notice that the line of the crack as "blown" out, ie there is a raised surface along the line of the crack, about 40 mm wide, and it sounds "drummy" again. Did I do something wrong ? EDIT: the "blown" line has appeared during Summer ( not a dry summer tho!), after the reapir in Winter, so maybe the crack has contracted, while the new material remained rigid, resulting in the Blistered appearance ..??
    Last edited by cubic; 6th Mar 2011 at 02:36 PM. Reason: update :
    Thanks !
    Cubic H.

  9. #9
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    There is a product calle helicoil which i have used on several heritage restorations where brickwork has both vertical and horizontal cracking. it involves te removing of bed joints and/or perpends at 600mm centres for a length of 500mm and inserting a 'twisted' rod, after which the joint is refilled with a 4:1 mortar mix. i also added some bond crete to the mix to add to the 'stickiness' of the mix. Worked perfectly in the past, and has been approved by engineers!! Hope this helps!

  10. #10
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    Quote Originally Posted by cubic View Post
    Hm, interesting information in this thread...a few months ago, I "disappeared" several narrow cracks like this using either "Cornice Cement" or Spackfilla ( I had packets of both), but NO MESH because I didn't know about it, then repainting, which was OK at first ..but now, I notice that the line of the crack as "blown" out, ie there is a raised surface along the line of the crack, about 40 mm wide, and it sounds "drummy" again. Did I do something wrong ? EDIT: the "blown" line has appeared during Summer ( not a dry summer tho!), after the reapir in Winter, so maybe the crack has contracted, while the new material remained rigid, resulting in the Blistered appearance ..??
    I agree the crack has probably contracted and suspect that tape would not overly help prevent the blown joint in a brick wall due to such a cause/pressure. It is really only there to give the render something to bond to - not to stop movement.

  11. #11
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    The bulk of your problem is that you used cornice cement to fill the void. It expands and contracts at a different rate to the cement render around it. Cornice cement has a couple of uses, and as I've discovered the hard way filling cracks in rendered walls isnt one of them unless you are tarting the place up to sell and it wont be your problem when it falls out (having said that I filled a massive crack in an internal wall for a friend who wanted a quick, cheap fix, four years on its still good as gold, although Im pretty sure the cornice cement is the only thing holding that corner of her house up).
    Renovator is right, the mesh just helps to make sure it stays put not stop movement.
    Would I be correct in guessing that you didnt rake out the cracked mortar joints and re-point them?

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