Polished Concrete Flooring

[laurenco]

Hi,

 

We're planning a self build with an insulated EPS foundation and UFH on top, in the floor slab. Does anyone know if we can polish this floor slab up to make a polished concrete floor? and does this work out cheaper than say, tiling the floor, as we're not doubling up on materials?

 

Thanks

 

Lauren

[nod]

Polished concrete looks great 

It’s ideally used instead of screed on top of a concrete slab or block and beam floor

You can poerfloat 

The slab But would look quite industrial 

[Alex C]

This comes up quite often. A polished concrete slab that is poured and polished by a groundworker with no roof over the top is going to be rough at best and terrible if it rains or is cold/hot when poured. If you want a beautiful polished concrete floor you need a specialist contractor and it needs to be covered. As mentioned above the best results are actually a polished screed rather than structural slab.

[Bitpipe]

I looked into this, before settling on a timber suspended floor with resin on top - was about £100/m2.

 

The polished concrete guys needed a 100mm layer of concrete and cost was also about £100/m2  - this is for the mirror like finish effect.

 

You can also do a micro-screed on your 'rough' finished floor which was same as resin but only a few mm thick.

 

Large format tiles (800mm+)are about £50-60/m2 and labour £40-50 (two man job usually with specialist cutters etc) so they're all in the same ballpark.

[Declan52]

You can still put in your slab but it leave 75-100 mm lower. Then when your house is done and ready for the finished floor who ever will do your polished concrete floor will come in and work their magic.

As has been mentioned above it is definitely not a cheap option.

[Visti]

Be aware that there is a distinct difference in a power-floated finish and a polished finish.

 

A polished surface needs a specialist as @Alex C points out and will cost you significantly more but gives you the shiny smooth finish.

 

A power-floated finish is far cheaper and can generally be done by most main contractors. It isn't perfectly smooth (it'll have divets) but it'll be a decent matt finish if spec'd right (i.e. a good composition is used and the main contractor is aware that it's to be the finished surface). Edges will need some remedial work, there may be hairline cracks if it dries too quickly and marks from the power-floating machine may be visible. 

 

We've gone for the power-floated both for cost and because we quite like the idea of a bit of texture / matt-ness. Ultimately it comes down to personal taste and budget.

 

Below are some examples our architects showed us of a power-floated finish. The close up looks 'shocking' but is in reality not much to worry about. I know of some other members on here who have filled in any cracks and divets with contrasting resin which we potentially plan to do as well!

 

 

[laurenco]

Thanks so much everyone for your responses. This has been really helpful.

[jack]

We have polished concrete over a structural slab. We had to go for 65mm rather than the 75mm minimum suggested, and have ended up with a couple of cracks. I haven't tried filling them yet, but they aren't the end of the world.

 

A few things:

• As I said, the minimum is 75mm - thicker is recommended. That's a lot of concrete if you already have a structural slab underneath, but hey, concrete looks cool!
• The polishers can only get so close to walls. We did ours before plaster and skirting boards. Even so, there's a clear region along every wall that was polished by hand tools rather than the big grinders, and this does look different, and in a few places is slightly undulating. If you're happy with this (we are - we think it adds character), it isn't an issue.
• If you aren't happy with a different-looking edge, then the pouring and polishing needs to be done before the frame goes up. That allows the whole surface to be polished, so you get edge to edge consistency. You then have the not-insignificant problem of protecting the floor for the rest of the build, including while the frame goes up. 
• Whether you get polished concrete before or after the frame goes up, you will be protecting it for a long time. We used Correx throughout the ground floor. Even though we taped it at every edge, we can still see dark lines in some areas where the joins were, two years after moving in. Also, dirt and dust finds its way in, and can cause scratches.
• Polished concrete companies get their concrete from local suppliers. In our case, we wanted to see a small amount of exposed aggregate visible after polishing. We really didn't want black/dark aggregate, but the company couldn't/wouldn't make any guarantees about aggregate colour. Was fine in the end, but a risk, albeit slight (I've never seen black aggregate anywhere near where I live. We have numerous sand and gravel pits nearby and they all have light stone).
• Concrete can be tinted to whatever colour you like. We wanted something a little darker than one of the standard tints and the company was happy to come up with something custom. Again, it was to our risk whether we were happy with the colour when it was down - if the concrete had been yellower, for example, that would have changed the colour in a slightly browner direction, but in the end we got a nice warm dark grey along the lines we were expecting.
• Concrete is easy to keep clean, but even with a sealer it can stain. My wife accidentally left a bin bag on the floor overnight once, and some sort of fluid leaked out. We now have a large, permanent dark stain in the kitchen that's a bit unpleasant. I personally wouldn't have concrete in a kitchen again under any circumstances.

 

Would I go for concrete again? Not sure. I suspect that large-format tiles are a hardier long-term solution, but let's face it, they aren't polished concrete! If I had my time again, I think I'd perhaps tile the kitchen and have concrete everywhere else.

 

One thing I really like is how it feels underfoot in summer. Winter... less so, especially when the ASHP is on the fritz so the slab is unheated!

[le-cerveau]

We went for screed (Builders choice), we have 250mm concrete slab (Ground Floor) and 250mm concrete beams (First Floor).  Then 50mm liquid screed with the UFH pipes in, thicker on the First Floor due to camber of the 8m span beams, then another 50mm liquid screed on top (ducted electric cables in this one).  Teh screed was laid in 2 runs on advice to improve curing.  It is then topped with a microscreed finish this is the final floor surface (currently doing the Ground Floor).

 

I know completely over the top, but it works, the builders had structural concrete to work from for a long time, the screed was next, then plastering and the Micro Screed is the final work, just finishing off the second fix to go and the wood work (doors, skirting,...)

[mvincentd]

Also remember having ufh pipes in the main slab will likely alter the performance of the ufh compared to them being in a 50mm screed so factor that in.  For example my ufh sits directly in my slab which ranges from 200 to 300mm thick, so i'm not expecting to be able to adjust temperature at any kind of speed at all (not fully commissined yet).

[laurenco]

23 hours ago, mvincentd said:

Also remember having ufh pipes in the main slab will likely alter the performance of the ufh compared to them being in a 50mm screed so factor that in.  For example my ufh sits directly in my slab which ranges from 200 to 300mm thick, so i'm not expecting to be able to adjust temperature at any kind of speed at all (not fully commissined yet).

 

Is it less efficient to sink the UFH pipes into the slab? ie. does heating need to be on higher temperature all the time?

[le-cerveau]

1 minute ago, laurenco said:

Is it less efficient to sink the UFH pipes into the slab? ie. does heating need to be on higher temperature all the time?

Not necessarily, depends on your insulation.

It will be slower to react the further away from the surface it is, but depending on your house that may/may not be an issue.

[Dee J]

I do wonder about concrete finishes. If I look at the floor in the local B&Q, or in many exhibition centres, it appears to be a smooth satin concrete. Is that power-floated, polished or what? If I put a finish like that in my house (as part of the slab), what care and maintenance does it need? In the commercial setting it seems to cope with high stresses with little impairment. Thanks.

Edited March 1, 2018 by Dee J

[jack]

We sweep ours with a wide microfibre brush. Doesn't take long.

 

Other than that, we just do an occasional mop (probably not as often as we should, if I'm honest). Seems to work fine.