Attaching a small box to a roughcast wall.

Is there a special technique to drilling and mounting things on an external wall that has a roughcast render. It's very hard to get holes level or exactly where you want them!

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  • stuart45
    stuart45 Posts: 3,839
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    I'd use an angle grinder to cut out the shape of the box, and then knock off the roughcast. Render smooth what you have taken out, and then drill and fix the box to the wall.
  • I use a hammer to flatten the area that I'm going to fasten to a little bit. doesn't have to be perfectly flat but if you knock all the high lumps down it's a lot more stable.
    regarding getting holes in the right place, that comes with practice but I'd recommend doing one at a time, you can't really go wrong that way it just takes a lot longer. i.e, drill one fixing, fasten to the wall and level it, then mark another hole. remove, drill 2nd fixing, re-fit, mark 3rd fixing and so on.
  • Le_Kirk
    Le_Kirk Posts: 21,957
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    I would go along with the above; if you fix it in the right place, level it with a spirit level and do up the one screw tight. then, using a slightly smaller drill bit, drill straight through the other hole in the box, using the hole in the box as a guide.  Loosen the screw, swivel box out of way and drill hole the proper size.  Job done!
  • GDB2222
    GDB2222 Posts: 24,350
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    stuart45 said:
    I'd use an angle grinder to cut out the shape of the box, and then knock off the roughcast. Render smooth what you have taken out, and then drill and fix the box to the wall.
    Angle grinders are quite scary. 
    No reliance should be placed on the above! Absolutely none, do you hear?
  • stuart45
    stuart45 Posts: 3,839
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    GDB2222 said:
    stuart45 said:
    I'd use an angle grinder to cut out the shape of the box, and then knock off the roughcast. Render smooth what you have taken out, and then drill and fix the box to the wall.
    Angle grinders are quite scary. 
    That's a good point, they are potentially dangerous in the wrong hands. Easy to forget when you are experienced with certain tools that it might not be the best advice over a forum.
  • Eldi_Dos
    Eldi_Dos Posts: 1,543
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    Make a template out of strong cardboard with the position of required holes accurately marked.
    Get a small ( 2 or 3 mm) masonry drill bit, drill one hole and use template to drill others checking as you go along.
    When you are happy that the pilot holes are accurate use bigger drill bit till you get size you want.
    Use nylon standoff spacers between box and wall, these will give you a bit of play when putting bolts or screws in and 
    give a gap between box and render.
  • tetrarch
    tetrarch Posts: 245
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    This all sounds very complicated. Why not just use a hammer and chisel to knock the small stones out of the roughcast to make drilling easier. There is no need to level the whole area.

    Regards

    Tet
  • Eldi_Dos
    Eldi_Dos Posts: 1,543
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    One of the benefits of standoff spacers is any rainwater coming down the wall will not gather on the top of the box         which can lead to moss and mould forming on the box and the wall.
  • stuart45
    stuart45 Posts: 3,839
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    tetrarch said:
    This all sounds very complicated. Why not just use a hammer and chisel to knock the small stones out of the roughcast to make drilling easier. There is no need to level the whole area.

    Regards

    Tet
    None of the methods above are that complex. Cutting into the roughcast with a grinder down to the butter coat, hacking off and smooth coating is a standard method when fixing things like meter boxes. Roughcast walls can be really uneven, so it's not always just a case of knocking off a few high spots to get a box to fit flush to the wall. Hammering off without a cut break can also can put stress fractures into the topcoat which allow moisture into the wall. 
    The method described by Eldi_Dos would be a good alternative way.
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