New here, and i am a rookie home DIYer. Looking for some help

Me and a friend of mine(tradie who knows much more than me) have started trying to add a bathroom to an old double garage at the rear of my property. It is a circa 1950 home built with double brick. In order to connect the bathroom drainage ( shower, sink & toilet) to the waste line we had to cut two channels, one through the concrete floor and one trench outside running to the sewer access point. The problem lies when trying to connect the two under the existing wall through the concrete slab/foundation. We don't want to damage the structural integrity of the foundation and its so thick i am not sure drilling a hole big enough for the 100mm waste pipe to fit will even be possible. Any ideas would be great.... thanks

1 Answer 1


I did exactly what u describe. Take a circular saw with a diamond blade and cut into the concrete on the outside of the pipesize. Small increments at a time. Cut the complete depth of the blade. Than take a concrete hammer and get rid of the inside between ur two cuts. If u have to go deeper just continue with the hammer. Add the pipe and new metal reinforcement and concrete. The project was not much fun. 🙄🙄 The stability is not a concern. My project was 5 years ago. Prep you concrete that the old binds with the new. There are plenty of YouTube videos for that. There is also a binding compount. I used the mesh type of reinforcement but I did not connect it to the old concrete.

  • Thanks mate. Made it through! :) wan not much fun at all, ended up just punching through with hammer drill. plumbing is in with perfect slope. cheers
    – user110801
    Commented Jan 9, 2020 at 8:17
  • Great, it was character building I am sure 😄. If u think my answer was helping can u upvote it.
    – Ride Sun
    Commented Jan 9, 2020 at 15:43

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