Best tool to cut a slit in a wall?

[dent]

Hi all,

I need to cut a vertical slit at least 4mm wide through a 100mm wall, and up to a height of 3m from the ground (for a vertical DPC where a new extension joins a house). What is the best tool for the job? I have got a 230mm angle grinder, but that would only go to about 75mm depth, and is a beast to use anyway (i.e., I'd rather not use it up a ladder). I've seen a few hire shops can supply wall cutters (basically a plunge saw with a diamond blade), but these only go to about 50mm depth. Is there a tool specifically for this type of job?

thanks,

dan.

[Andrew Gabriel]

I'd have to say this sounds rather misguided in the first place. Who advised doing this, and for what purpose? Has a structural engineer been consulted on the weakening of the wall?

[Jules]

I saw a wall cutter once on TV - walls were a good 2ft thick. Crew had to make their own rig to support it and guide it, then attach it to the wall with some serious concrete anchors. They do exist, but possibly outside the realm of hire shops :-)

re. angle grinder, can you access both sides of the wall? If so, drill a couple of guide holes so you can line everything up and then attack from both sides (and maybe source/hire a scaffold platform - or at least make sure your ladder's secure; maybe anchor it to the wall and patch up afterwards?)

cheers

Jules

[dennis]

There is a subcontractor doing just that on a lot of Smiths houses near my parents (to demolish one half without affecting the other half). They have a jig they bolt on the wall and then cut it with a diamond saw. Without the jig it would be difficult to do a straight cut.

With care a big angle grinder would work but you are going to want a jig of some sort.

[dent]

Local Building Control told me I had to do this. I omitted it on my original plans, and they only passed the plans on the condition that this was added. It doesn't seem to be unusual to do this (e.g., see

[Stuart Noble]

I'm sure he means "into" rather than "through" the wall :-) Angle grinder is the norm but keeping the cut straight isn't that easy IME

[dent]

Unfortunately not. It's a cavity wall, and I only need to put the slit through the outer cavity.

thanks,

dan.

[Bolted]

Diamond chainsaw. They are great fun, but it might be hard to avoid the temptation to saw the rest of your house into small pieces. They can be hired, but they are a little hard to find (the place I used was just about to stop doing them, so I can't recommend anywhere).

[Andy Dingley]

Diamond wiresaw, surely? I though diamonds didn't like chains as there was too much shock loading. Even then, those are usually kept for concrete with hard aggregates as brickwork will succumb to a far cheap wheel.

I sometimes use a chain morticer with a carbide chain that costs an indecent amount. I imagine these make even that look cheap.

[Bolted]

Wire-saws need access from both sides, I think.

I said (and meant) chainsaw. The one I hired was an ICS 14 inch petrol one but they do some truly impressive looking hydraulic ones too

was cutting concrete (extension with a raft foundation with walls sitting on a cast concrete upstand to DPM level, builder cocked up and set the gap in the upstand 300mm too narrow).

Much easier to control than a big disk cutter, especially if not cutting along the ground.

I think they are around the =A3150 mark for a new chain. Chain wear was a significant proportion of the total hire charge for me.