Floor grinding

[Canski]

Some of you may remember the cock up of a cemfloor that I had pumped in last year with dips and cracks etc. 
Well now the time to get it flat is coming near and I need to start thinking about getting it flat prior to tiling and wood flooring. 

I have a couple of areas ( around 5m2) that are about 15 mm low and a  bump in the middle ( around 3 m2) that is around 10 mm high. In addition to this the whole surface has stones sticking up around 2 - 3 mm above the flat surface of the concrete. 
 

I intend to use a decoupling membrane under the tiling and an approved underlay under the engineered oak flooring. 

My questions are :-

 

What machine have you guys used to grind the floors down ? Will I do it in a day ( 85 m2) ? I’d like to use a window of opportunity given to me by a delay in my plasterers returning. 
 

Would it be ok to level the floor using levelling compound between the raised aggregates after removing the high spots or should I try to grind them out ?

[Jenki]

I think a combination of grinding and leveling is the best bet.. I did similar with mine. Where I had some edges of the slab needed grinding and then leveling out.

[JohnMo]

I had some high and low areas., low self leveling compound.

 

High an angle grinder attachment from Screwfix and a Henry hoover (lots of bags), then some 2 or 3 days grinding away.

[jack]

I used a floor grinder to grind back the spalled surface in our garage before I laid an epoxy coating. It was surprisingly expensive taking into the account the wear charge on the diamond cutters. I want to say it was something like £800 for the weekend, half of which was wear, but I could be wrong about that.

 

I'd have a word to a grinder hire company to find out the cheapest way to roughly remove high spots. It's not like you're after a polished finish.

 

Also, some of those cracks are a bit unpleasant looking. Would you consider drilling the ends to stop them spreading, and filling with something like epoxy to stabilise?

 

Another thought: are you certain you can't just cover the entire thing with self-leveller? Does it matter if the finished floor level is a bit higher? Are there any dependencies on that level that can't be adjusted to account for a slightly higher floor? Might be cheaper and easier than lots of grinding and localised levelling.

[Canski]

18 minutes ago, jack said:

Also, some of those cracks are a bit unpleasant looking. Would you consider drilling the ends to stop them spreading, and filling with something like epoxy to stabilise?

Since the photos were taken there has been a lot of traffic and debris on the floors and now its all been swept up the cracks are no longer noticeable. The cemfloor had fibres in it so I am confident it will hold together ok.  When I get my laser back from the lads I will do a survey of the floor and if there are only a few high spots I'll try and grind them out with a stihl saw and see if I can get somewhere near.