Polished concrete floor with underfloor heating. What are the steps?

[flanagaj]

I really want to have underfloor heating and a polished concrete floor, but I am struggling to understand the stages to accomplish this.   Can anyone shed some light as to the various layers and at what point in the build you do them.

For example, I was under the impression it was hardcore / sand blinding / membrane / insulation / underfloor heating pipes clipped to insulation / slab / screed.   So for a polished concrete floor, you just pour a deeper slab (omit the screed layer) and then get it power floated, before grinding it according to the desired finish.

 

But when I look online, I see images of the pipes sitting above a concrete slab?

 

 

[markc]

Depends what finish “look” you are thinking of, structural slab generally has large aggregate, others prefer the ground surface to have much smaller and/or coloured aggregate and much closer together (less sand/cement) so a screed layer (but concrete) over the structural slab

[Joey]

We want a similar floor finish on our project, but I haven’t got as far as contacting concrete flooring contractors yet so can’t help with the polished concrete per se, however have you considered alternatives such a microcement? As markc says, it depends what look you want specifically, but this might give you much more control over the finish and be logistically simpler?

 

We’ve been quoted £8,000-9,000 for 80m2 from a local, relatively high end, contractor. Sure others could do it for less, but as I understand proper polished concrete is also very expensive. We’re definitely moving towards this over polished concrete, but I’ll be happy to pass on any information I get regarding the later when I get round to enquiring!

[nod]

You would do your block and beam and slab as normal Treat the polished floor as a screed to be done when you are fully watertight just before first fix 

You will also need to budget to protect the floor with ply 

 

It doesn’t tend to workout much different in cost than a good quality tile 

[saveasteading]

7 hours ago, markc said:

structural slab generally has large aggregate, 

Because its strong and cheaper. But you can specify for smaller stones.

[jfb]

I’ve done a couple of diy exposed aggregate concrete floors to good success. You are correct that you just need to omit the screed and go for a slightly thicker slab. 
I hired a grinder and spent a week grinding down (I threw in some larger stones after the pour as well), then going through finer grits. Would have been easier if the pour had been more accurate. Didn’t power float mine but if doing again would try to make more effort to get the pour flatter.

good luck!

[deancatherine09]

We are going with microcement. Bought the kit from Relentless for 120sqm for just under £3k for the whole of downstairs and going to apply ourselves. Ours is an insulated raft with power floated concrete / UFH already in so the microcement will just sit on top.

[flanagaj]

On 11/02/2024 at 23:19, jfb said:

I’ve done a couple of diy exposed aggregate concrete floors to good success. You are correct that you just need to omit the screed and go for a slightly thicker slab. 
I hired a grinder and spent a week grinding down (I threw in some larger stones after the pour as well), then going through finer grits. Would have been easier if the pour had been more accurate. Didn’t power float mine but if doing again would try to make more effort to get the pour flatter.

good luck!

This has got my attention.  Did you do a simple hardcore / blinding / membrane / insulation / concrete floor and if so, did you do the pour?

I have a large 157m2 slab and was planning on not having sleeper walls.  Concerned that as it's quite large with a 7m span across the width, that it might be a job for a professional contractor.  I had a quote from a reputable contractor, and it is was working out at £152/m2.   That is for them doing the pour and then the subsequent polishing.   If I could get that down to £120/m2 then I probably would just get them to do it.

Will save a great deal of time not having to tile floors too.

[jfb]

5 hours ago, flanagaj said:

This has got my attention.  Did you do a simple hardcore / blinding / membrane / insulation / concrete floor and if so, did you do the pour?

Yes as you describe. I did the pours as well. The actual polished area was only a max of about 40m2 though.
had to do the whole as house at the same time so certainly could have laid a more level floor! Definitely not the most straight forward to get things super level. and much harder over a larger area.

would be interesting to know what margin for error the contractor offers (maximum mm discrepancy over the whole area).

 

also you have to factor in some expansion joints. I have some minor cracks in mine as I didn’t have any but no big deal for my place.

[saveasteading]

28 minutes ago, jfb said:

margin for error the contractor offers

Lay down a perfectly straight timber 3m long. Measure the gap, both sitting naturally and with each end pressed down, and the opposite end rising. 3mm maimum is required in warehouses and sports halls. Worse than that is OK in a house.

If it looks OK then it is.