I need to add an extractor fan to our utility room so I started drilling a hole using a core drill bit from the inside to outside. Its a standard UK brick cavity wall, so brick > insulation > brick. I got through the inner brick wall no problem, but when I started going through the outer wall, rather than cutting the brick I actually ended up pushing the brick out slightly.

After going outside to check, I realised the mortar had vibrated out while drilling, so I re-pointed up and left it a week to dry. Tried again, being quite light on the pressure and same thing happened again. I'm about a third of the way through the second row of bricks.

What can I do to stop these bricks pushing out while I'm drilling the bore hole for the extractor fan?

View from outside View from inside

1 Answer 1


I would suggest re-doing the cement for the bricks, allow to dry.

Then once hard I would secure a wood panel (12" or 15" square) over that area to help hold the bricks back.

Then drill gently.

  • +1 for backer board. The backer board is the key but i would drill it first and then re-mortar so the new mortar does not get vibrated loose again.
    – Alaska Man
    Commented May 4, 2019 at 20:15
  • Or if you were in a rush, chain drill around the perimeter with a small bit from the outside and whack away at the brick with a hammer. Then mortar etc. Commented May 4, 2019 at 21:11

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