Grinding concrete

[shedfooting]

I am planning some modifications to achieve a combined wheel chair accessible toilet and shower area in our older home, which is on a concrete slab. In an area about one metre by one metre, a want to grind the slab surface from zero mm around the edge, to minus 20mm in the middle for water drainage at that central point.

Question is, how should I attack this grinding task? What king of equipment will enable me to do this. I am a competent handyman.

[Beardy]

Hire a floor grinder with all the dust extraction gear attached or if you want a more basic approach use a cup grinder wheel in a grinder

Just a moment...


Then there are finer polishing grades to get a finer finish

[Bushmiller]

shedfooting

There are quite a few ways this could be done, but with all methods the big thing is the dust so you either have to have good dust extraction as Beardy has pointed out or you need PPE including dust masks and eye protection Actually even with dust extraction you need PPE too. To minimise dust and only using what I have, I would use an angle grinder with a stone cutting blade. Make a series of cuts in the concrete starting in the middle and radiating towards the out edges. Imagine a spiders web to visualise what is happening. Experiment to see how many cuts you need, but perhaps arrange the cuts to achieve a 50 mm interval by the time you reach the outer edge. Use a cold chisel or brick bolster to chip away at the cuts. Once this has been roughed out you can use the cup grinding disc to even out and develop the surface. It does not have to be perfectly even as you will be waterproofing and possibly tiling on top of that so waterproof slurry and tiling adhesive will even the surface.

Also have a metal cutting disc on hand as towards the centre you may go deep enough to contact the steel reinforcing mesh. You will have to cut through that. The concrete blade will cut small amounts of metal, but the dedicated blade will be better.

Regards
Paul

[419]

What Beardy and Bushmiller said.

Especially about the dust. In a very short time you can be working in clouds of dust that reduce visibility and breathing to dangerous levels. Think about hiring a high volume dust extractor which can be vented through a window.

Also, seal the room when working. Even then it's surprising how some dust can still get into the rest of the house.

Get a disposable overall and leave it and your footwear in the room when you're finished, or finished a session. Better to leave as much dust in the room as possible, because concrete dust is very abrasive and domestic vacuum cleaners don't like it.

[mic-d]

I recently had to look at grinding some concrete in a room about 4 sqm to max 15mm deep. I rang a couple of hire shops with big grinders but both warned me that this was not the job for the machine and i'd go through a lot of diamond wheels. This is the sort of tool they were talking about Floor Grinder hire | Sumner Park
They said the tool for the job was a concrete scarifier from Mega Hire. (in the end it was better for me to go the other way and level the floor up to the high points with compound)
Cheers
Michael