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  1. #1
    Join Date
    Aug 2007
    Location
    Melbourne
    Posts
    4

    Default Drilling holes into soft concrete footing

    If you pour concrete footings for a deck is it ok to drill the holes
    for the dynabolt while the concrete is hardening (not wet) using a normal
    12mm drill bit, or should I wait till the concrete is rock hard and then use
    a hammer drill to make the holes.

    I guess the first option seems easier and less disruptive to a new footing.
    I'm worried using a hammer drill will weaken a recently poured footing.

  2. #2
    Join Date
    Jun 2006
    Location
    East Warburton, Vic
    Age
    54
    Posts
    3,542

    Default

    You will never drill a hole with a normal drill bit.

    Let the footing cure for a couple of days then drill as per normal with a hammer bit. It won't affect the concrete or weaken it
    Cheers

    DJ


    ADMIN

  3. #3
    Join Date
    Oct 2003
    Location
    Kentucky NSW near Tamworth, Australia
    Age
    86
    Posts
    1,067

    Default

    The biggest problem in drilling green concrete is that you probably have an 80 to 90 % chance of hitting blue metal in the concrete and this will make the the drill bit run off because the cement not being cured you will have a hole bigger than what is required to get the maximum strength for your dynabolt.

    There is more chance of doing more permanant damage to your footings.

    It takes 21 days for concrete to cure properly.

  4. #4
    Join Date
    Jan 2004
    Location
    Over there a bit
    Age
    17
    Posts
    503

    Default

    Wow, only 80-90% chance. Seems more like 115% of hitting the blue metal and only slightly lower for getting the reo mesh.
    Boring signature time again!

  5. #5
    Join Date
    Aug 2007
    Location
    sydney
    Posts
    29

    Default Wet VS Dry Brackets

    I asked a question a few weeks ago about puting the dynabolts straight into the the wet cement and just let them set so I would not need to do any drilling at all, I was advised if to use Wet fix brackets...

    Are wet brackets just as strong as dry if so why use dry ones if you could cut out all the time and drilling ?

  6. #6
    Join Date
    Oct 2003
    Location
    Kentucky NSW near Tamworth, Australia
    Age
    86
    Posts
    1,067

    Default

    I've never heard of a wet fix bracket unless you mean a post stirrup, "J" Bolt or a "U" Bolt. If so these would be much stonger than any drill in anchor that is including chemical anchors.

  7. #7
    Join Date
    Oct 2006
    Location
    Tallahassee FL USA
    Age
    82
    Posts
    0

    Default

    You betcha, Bazza. The cast-in bolts put more uniform stress on the concrete. The only advantage of drilled-in anchors is accuracy of placing, i.e. measure location, then drill. If the anchors are near the forms, support them with scrap timber attached to the forms at accurate locations. Elevate the scrap with spacers to finish the concrete around the anchor. Much better construction IMHO. For distant locations, e.g. interior of the slab, drilled-in is probably better though, unless you can position cast-in anchors accurately (good luck on that).

    Joe
    Of course truth is stranger than fiction.
    Fiction has to make sense. - Mark Twain

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