Power floated slab. Now rethinking micro-cement

[-rick-]

13 minutes ago, saveasteading said:

Thanks for the link. It looks good in the pictures of course.

I'd expect that the ground surface needs to be sealed.

 

It does, they provide that.

 

13 minutes ago, saveasteading said:

Also for it to be hideously expensive. Have you asked?

 

Not asked, but they do claim to be one of the most cost effective floor options. Part of why they claim that is their polishing system is different from every other one I've seen (though I'm not sure if its unique or just less common). They have grinding discs that fit onto a powerfloat and so don't need the traditional floor grinder to polish the floor. Claim an 80% time reduction for polishing.

 

13 minutes ago, saveasteading said:

Power floats are big, with a circular sweep. How do they reach into corners?

 

Have them do the work before you build walls. At least that's my thought. There are of course other options if thats not possible down to hand held size.

 

I know people on here seem to have an aversion to Tim @ The restoration couple possibly because he does accept some sponsorships but he has done a dry shake floor (not Concria) and has a few videos on it that are pretty informative. He is doing that massive building on a ~£200-300k budget. Obviously a smaller building would be a different situation but it's still useful.

 

 

 

[jack]

On 08/09/2025 at 12:26, -rick- said:

Thanks for posting @jack lots of useful info here. Apologies in advance for all the questions below! Hope all this is relevant to @flanagaj's original point and I'm not diverting things too far away.

 

It's all relevant to the topic, so no issues from my perspective.

 

On 08/09/2025 at 12:26, -rick- said:

Sounds like you actively chose polished concrete over other options for it's look rather than cost. Is that right? If so what guided your decision?

 

Partly aesthetics, partly function (easy to clean, good for UFH). It was not a particularly cheap option. I think it was comparable to getting decent wood flooring installed, but it's been over 10 years so I don't remember.

 

On 08/09/2025 at 12:26, -rick- said:

Indeed. Do you remember any more details about what you got? Was the screed a normal cemfloor type? Did the mix have fibres? Did they top it with stones/minerals for the look? Or a dry shake?

 

No, it's ordinary poured concrete. It had a tint added, so it's slightly darker than regular concrete. No fibres (wouldn't they show on the surface?). It had the aggregate mixed in. I don't remember them doing a dry shake, but it was a long time ago. Certainly no stones were visible after power floating. It took quite a bit of coarse grinding to start exposing the aggregate, and even after that, there are areas with little to no visible aggregate. To be fair, that outcome was partly driven by my wife, who didn't want a lot of it visible. 

One of the things that might have contributed to the couple of cracks we have is that our nominally 65 mm thickness is 10 mm less than the recommended minimum. They did warn us in writing of an increased risk of cracking, so I can't really fault the supplier.

 

On 08/09/2025 at 12:26, -rick- said:

I've seen in torches used non-domestic settings to burn off the stains from the concrete. Is that a possibility that's been mentioned to you? I have no idea if its something thats even an option on a polished/domestic floor and I assume it would introduce the possibility of cracking. I assume the stain seems to have penetrated deeply so repolishing the area is not an option?

 

No-one's suggested torching, but the big stain is almost certainly too deep to be torched or polished out. I've considered repeatedly applying and mopping up a solvent to see whether that would help, but it's so far down the (long!) list of life priorities that I'll probably never get to it.

 

On 08/09/2025 at 12:26, -rick- said:

One of the attractions to me was that concrete is a hard wearing surface and it's disappointing to hear you've found staining to be such a problem. Some of the dry-shakes marketing is around making the surface more stain resistant so something for me to look into further. 

 

I'm definitely of the view that you need to plan up front for the possibility of wanting to cover it in the future and set levels to allow it. Meeting the level entry requirements at the same time is tricky but I think doable.

 

 

*Thumbs up*

 

 

[jack]

2 hours ago, -rick- said:

Have them do the work before you build walls. At least that's my thought. There are of course other options if thats not possible down to hand held size.

 

100% should be done before walls if you want an even result.

 

Also, my recollection is that (at least with actual concrete) the grinding needs to be done within a certain period of pouring - from memory it was within a few days of pouring. After that, it hardens so much that it takes a lot more work and diamond stones to grind and polish.

 

One other thing I forgot to mention: we were advised to keep it covered for as long as possible. We bought a load of correx sheets, laid them down, and taped all seams. Weirdly, ten years later you can still see lines showing where the joins were. I have no idea whether the joins allowed the underlying concrete to cure and/or dry out faster, but it's something to think about. To be fair, I'm the only one who notices them.   

[-rick-]

32 minutes ago, jack said:

No fibres (wouldn't they show on the surface?). It had the aggregate mixed in.

 

On the type of floor you got with no dry shake yes they would. Even with dry-shake some visibility is possible though the dry shake layer helps hide the bulk. Offset with that potential visibility is the potential to reduce cracking, etc.

 

32 minutes ago, jack said:

I don't remember them doing a dry shake, but it was a long time ago.

 

Sounds like your company coloured the concrete rather than dry shake. If you were going for an exposed aggregate finish rather than a specific decorative topping that makes sense.

 

27 minutes ago, jack said:

One other thing I forgot to mention: we were advised to keep it covered for as long as possible. We bought a load of correx sheets, laid them down, and taped all seams. Weirdly, ten years later you can still see lines showing where the joins were. I have no idea whether the joins allowed the underlying concrete to cure and/or dry out faster, but it's something to think about. To be fair, I'm the only one who notices them.   

 

Good to know. I noticed that Tim (mentioned above) put down large polyethylene (or similar) sheets under the correx maybe that mitigates that. I will be keeping a close eye on his videos for when he gets back to finishing the floor (though whether it would be noticable enough for video IDK)

[saveasteading]

5 hours ago, -rick- said:

Have them do the work before you build walls.

Aargh. You will be rain and wind affected, and every dog, cat,  fox and seagull from miles around will visit and walk over the wet concrete.

[saveasteading]

On 08/09/2025 at 11:25, jack said:

don't know what the process for taking up the whole screed would be

You simply would never do that. Raising all the doors would be preferable.

Epoxy coating would work. Grey isn't so different from the original colour.

 

@jackive just read your contribution. Hearing of your experience is so very instructive.

 

I possibly come over on such posts as negative. The contrary is the case. I have sought design and site innovation and invented processes In business and self builds. But I do lots of homework first and try to foresee issues. 

Then on here try to balance my negatives with the sales pitches that new builders have been sold.

Show me good results and I'm delighted.

[-rick-]

31 minutes ago, saveasteading said:

Aargh. You will be rain and wind affected

 

True, if I manage to get to the point where I'm actually building something then one of the benefits I will have is that I won't be time constrained (at least not conventionally) so I would want to schedule the slab where the odds of good weather are in my favour and definitely outside leaf fall. If the project needs to wait for that then so be it. Obviously this is not something that many can do so other tradeoffs may be needed.

 

I have thought about what could be done to protect the slab once it's down and done and think there are some good potential options there depending on site* so weather is only a huge concern during the first 24-48 hrs.

 

* still need to think more about this though

 

31 minutes ago, saveasteading said:

every dog, cat,  fox and seagull from miles around will visit and walk over the wet concrete.

 

I haven't thought about this so much but from what I've seen when doing a floor like this the concrete guys are pretty much constantly working from the pour to the point where the slab is hard enough to walk on without leaving a mark. With maybe a few hours break before the powerfloat gets on the slab (the powerfloat of course being able to flatten off a lot of minor marks). Have I misunderstood something?

[jack]

14 minutes ago, saveasteading said:

You simply would never do that. Raising all the doors would be preferable.

 

The doors that would need raising include:

• a 5.5 m long, ~900kg (according to the installer), flush threshold, triple-glazed slider, which is built in behind a wooden facade.
• two large, flush threshold, triple-glazed window doors.
• a 2+ m high, one-piece front door assembly with door and side window.
• two large, triple glazed windows with lower frames flush with the floor.

The screed is on a slip membrane, so easy enough to separate from the underlying slab. While cutting it out would be messy and unpleasant, it seems to me it would be a much more straightforward and lower risk job.

 

14 minutes ago, saveasteading said:

Epoxy coating would work. Grey isn't so different from the original colour.

 

Epoxy coating would be a lot of expense to avoid looking at a few stains. I also don't much like solid colours on floors, as I think they show every bit of dirt and wear. That's why we went for concrete in the first place!

 

Personally, I doubt I'd ever be able to justify the cost of replacing or covering the entire downstairs floor. I might, however, get just the kitchen done at some stage, since that's where 95% of the problems are. Can't see it happening for at least 5 years based on current household finances!

[Tom]

3 hours ago, jack said:

Weirdly, ten years later you can still see lines showing where the joins were. I have no idea whether the joins allowed the underlying concrete to cure and/or dry out faster, but it's something to think about. To be fair, I'm the only one who notices them.   

 

I covered our newly poured/powerfloated floor with 9mm OSB and the concrete guy nearly had a fit when I told him - he told me to take them up straight away and put woven dustsheets under the boards or the concrete would get "tattooed" by the sheet edges. Anyway, they were like that for over a year until polishing and no lines visible.

[saveasteading]

19 minutes ago, jack said:

Epoxy coating would be a lot of expense

Not necessarily. I once proposed to a garage owner that he used a simple epoxy  floor paint instead of what his original designer / car manufacturer specified. Downside repaint a small section of tyre wear in a few years.

Upside. ..  10sof £k saved. Diy work, no closures.

It isn't all expensive or thick.

 

24 minutes ago, jack said:

2+ m high

2m tall people have learned to duck.

[jack]

34 minutes ago, Tom said:

I covered our newly poured/powerfloated floor with 9mm OSB and the concrete guy nearly had a fit when I told him - he told me to take them up straight away and put woven dustsheets under the boards or the concrete would get "tattooed" by the sheet edges. Anyway, they were like that for over a year until polishing and no lines visible.

 

That could well be what happened.

 

15 minutes ago, saveasteading said:

It isn't all expensive or thick.

 

I know, I did my garage floor with it.

 

That isn't what I meant by "expensive". My main point on epoxy is that I don't like how it looks. As such, all I would achieve by putting it down is covering some stains. Even the modest amount it would cost to lay epoxy just wouldn't be good value (to me) in the circumstances.

 

22 minutes ago, saveasteading said:

2m tall people have learned to duck.

 

The door opening height wouldn't be affected. The problem would be that the unit is in one piece (including threshold) and difficult to move.