On 11/18/2016 1:02 AM, John Rumm wrote:
On 17/11/2016 19:45, Andrew Mawson wrote:
OK chaps - suggestions please.

I need to cut a 12" diameter hole in a workshop wall construction of
which is a single skin of 9" x 18" x 4.5" 7 newton concrete blocks. Now
I've all sorts of drills, angle grinders, hammers and even demolition
breakers, so the problem isn't removing the material, the problem is
doing it without the wall collapsing !!!

12" is really not a large hole - old boiler flues were frequently as
large as this.

Stitch drill and break out the middle with a SDS would be one approach.

If you want a neater round hole, overlapping core drilling also works.

You may be able to hire core kit large enough to do it as a single core.

Alternatively just chisel out the mortar and remove hole blocks, then
fill in round your exist pipe with new mortar and bricks (or bits of)


There are also firms that specialise in this kind of thing. A local one
here for example:

http://kssdiamonddrilling.co.uk/diamond-drilling/

(they claim they can do a 1.5m hole!)

(this is for a huge 3900 cuM/Hour extractor for a CNC plasma table down
draught exhaust)

Now this sounds like fun ;-)


My first thoughts are that either stitch drilling or removing one block
and making good afterwards would be fine.

But also agree with John about diamond drilling. One of my lads just
converted a shop unit in a modern complex into a bar, which meant
putting in loos on two floors. He was convinced the only solution for
one loo was a macerator because of the building geometry. I pointed out
that a six inch hole in the concrete floor (about a foot thick) would
give an easy run for conventional soil pipes. A local firm did it for
him for £300 in a couple of hours (that includes all the humping of kit
and cleaning up afterwards). I think the price would have covered half a
day's work, which was their upper bound estimate if there was much rebar.