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Putting holes in concrete blocks

Roger_S39 | Posted in General Questions on

Hi all,

Is there a better way to put a hole in concrete blocks for utility pipes etc. rather than just busting a rough hole in them?

Ideally, it would be great to be able to buy specialty blocks for this.

Something that gave an option of the hole being off center so when you reversed the block it would line up with the hole in front of it – as the two rows of blocks are off center to each other.

Also, are there any concerns, or important steps to take, once holes are made in this rough manner?

The blocks are used to build stem walls and filled with aggregate and concrete to create a slab.

Thank you.

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  1. Expert Member


    A couple of easy options are to either work your way around the circle you have marked with a hammer drill and masonry bit, or buy a diamond tip coring bit of the right size.

  2. Expert Member
    NICK KEENAN | | #2

    Holes for pipes or wires through concrete should be sleeved. You can buy pre-formed sleeves, or just use a plastic pipe one size bigger. Make the rough hole slightly big, and put the sleeve in and fill around it with mortar. Then run the pipe.

    1. Expert Member
      MALCOLM TAYLOR | | #3

      Really good point!

  3. Expert Member
    BILL WICHERS | | #4

    For small holes under maybe 1” or so, I use carbide tipped masonry drill bits. For larger holes, I use carbide coring bits. I use SDS-plus and SDS-max (larger shank) bits in Bosch rotary hammers. You can get carbide drill bits in sizes much larger than 1”, but the coring bits drill faster and cleaner for larger holes.

    Using the SDS system, which is not proprietary to just Bosch, makes drilling in masonry MUCH MUCH easier since you’re not constantly tightening the chuck on your drill. The bits seem to be better quality too, although I’ve used mostly Bosch bits so I don’t have a lot to compare them to.

    To center holes, you can place solid blocks in the spots you need to drill holes, that way you can drill the holes wherever you want in the block.

    I agree with dccontrarian too, it’s always best to sleeve things passing through masonry walls. The easiest way to do this is to use pieces of EMT conduit as sleeves, making sure the pipe or wire you are running will fit inside the conduit size you use to make the sleeve. Set the sleeve in place with grout or caulk, commercially this is usually done with an intumescent fire rated caulked. If you are penetrating a wall that is also acting as a fire barrier, you need to seal the gap between the pipe or wire and the sleeve too, which can be done with the intumescent caulk, sometimes using mineral wool as a backer, or with a clay-like fire stop material that come in small sheets.


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