On Tuesday, August 16, 2016 at 4:21:42 PM UTC+1, GB wrote:
On 16-Aug-16 4:17 PM, jim wrote:
"Dave Plowman (News)" Wrote in message:
In article ,
wrote:
Hi again,

I want to cut a hole for a new window in my house. It's got fairly
standard cavity walls, built of concrete blocks. Actually the blocks are
somewhat non-standard as they have foam insulation inside them (I mean
inside the actual blocks - not inside the wall's cavity.) The only
masonry-cutting tool I own is a 9" angle grinder. This will cut concrete
blocks no problem, but only to about 3" deep. I suppose could hire a
300mm grinder for about £28 a day plus the cost of the cutting disk
which I'm guessing won't be at all cheap.

Rotary grinders in general make an insane amount of dust. Is there any
other tool that anyone can recommend? (I'm visualising something like a
very large jig-saw with a diamond blade...)

Thanks for any tips you can offer,

Mark out, and carefully drill a hole (at right angles to the wall - use a
set square etc to check) right through at each corner. Join up the holes
inside with a pencil, etc. Cut from both sides with your angle grinder..


Erm it's a cavity wall?!

Once you've got nice neat lines from the angle grinder inside and out,
can't you just chisel out the rest?

Yes, I probably could. In the past, I've cut through a 4" concrete block wall using my 9" angle grinder, but this was close to ground level. I've never attempted a cavity wall before, and the desired hole is for a first floor window, so I'll be doing the outside using a ladder. Nightmare job for a retiree like me!

Thanks to the other responders also.

JD