General: polished concrete flooring ?

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- CommentAuthorwomblepaul
- CommentTimeJan 25th 2009
I have been researching options for floor finish on my farm house renovation in Wales.

I have installed the underfloor heating but not screeded the floor yet.

I want to screed the floor next week and was interested in polishing the screed as i like the finish and it seems about as ecologically sound as possible when compared to quarrying slate, importing bamboo etc etc.

I need to make a decision in the next few days as I need to decide on the thickness of the screed based on how I finish the floor.

Has anyone here polished a concrete floor ? It seems very straightforward to me but I can't find any one who has done it themselves...

Can you polish a screed ?

Does anyone know where you can hire the grinding polishing machines etc.

Thank you

Paul
- CommentAuthorselly
- CommentTimeJan 25th 2009
mate, your using concrete anyway so don't worry about being green excessively.

Old slate quarries can be great wildlife havens so I'd say but the natural slate floor and use lime as the adhesive and grout if you want to feel better.

Or wood from a sustainable source.
- CommentAuthorwomblepaul
- CommentTimeJan 25th 2009
I am well aware of the negative aspects of concrete.In hindsight I would have preferred a limecrete floor . But was not aware of this product when I poured the slab.

I don't think there is an alternative to concrete screed with the depths I am restricted to.

Most of the affordable slate comes from Brazil or other far flung places which is considerably more un environmental than the use of some electricity and cutting discs to polish a concrete floor.

Not convinced about the wildlife havens in a modern quarry and as I said costs/availability of flagstones welsh slate etc is completely beyond my finances

Reclaimed wood is not ideal with the underfloor heating and I still have to screed the UFH pipes anyway so no benefit on eco grounds.

Polished concrete seems like the best idea still..

Any thought anyone

Paul
- CommentAuthorCWatters
- CommentTimeJan 25th 2009 edited
Do make sure you get the right screed. On another forum we recently heard of someone who was badly advised to use an air filled screed. They'd put marble flooring on top and then discovered the UFH wasn't working. The air filled screed was acting as an insulator with return and flow temperatures virtually equal.

As for polishing I imagine the same applies - probably needs to be the right type of screed. Sometimes polyethelene (?) fibers are added to screed to reduce the risk of it cracking. I imagine these fibers would alter the ability to polish the surface. Talk to the company supplying the screed, see if they can recommend something then google it.

Our builder went to great lengths to cure the screed correctly (for example covering it with plastic to control the drying rate) but we still managed to get a few cracks. Typically these occured where the screed in two rooms met at a doorway. The two areas of scree shrank away from each other but unfortunately the crack isn't a nice straight line across the doorway. Consider using a strip of metal or some other means of isolating the two area of screed so the "crack" goes where you want it.

Google found
http://www.diynot.com/forums/viewtopic.php?t=6527

I think I would make sure that if the end result was a disaster I could lay polished concrete tiles on top and the levels would still be ok.

http://www.channel4.com/4homes/diy-self-build/diy-build-advice/a-z-of-diy-building-guides/hard-flooring-guide-concrete-08-07-11_p_1.html
- CommentAuthorwomblepaul
- CommentTimeJan 25th 2009
Thank you

I was aware of the Polypropylene fibers and will check before trying to polish the floor.I wasn't aware of the air filled screed issue but I will make sure I steer clear of this.

I will look further into the cracking possibility and decide whether I will pour the screed of get a contractor and a product that wont crack.

I have looked at this thread already(but many thanks) and need to find out if I can get a polished floor by this dedicated trowelling , but my initial findings suggest it will not be sufficient.

looking at various polished floors on the web (mostly in the USA) it seems some really fun stuff can be done with pigments,shells etc etc .

Has anyone tried to polish the concrete themselves ?

Paul
- CommentAuthorbot de paille
- CommentTimeJan 25th 2009
how big is the floor? you could hire a mechanical polisher

why cant you do a lime screed ontop of the slab??
- CommentAuthorwomblepaul
- CommentTimeJan 25th 2009
The floor area is 100 sq meters.

Yes want to do just that but would love to speak to someone who has tried the to do the same thing.

I will look into lime screed....

But I don't think I could polish this ?

I am also not keen on using Brazilian/ chinese slate etc. So The polished concrete/lime screed floor would be a great option I think.

There is some info on the web re polishing a concrete floor but mostly companies that suggest polishing concrete floor is not for DIY.

It seems to me as simple as sanding down floor boards, just more time consuming ... But I have never done it so don't really know.

Paul
- CommentAuthorbot de paille
- CommentTimeJan 25th 2009
Lime screed can certainly be polished and even finished with bees wax
- CommentAuthorwomblepaul
- CommentTimeJan 25th 2009
I can't find any info on Lime screed polishing? I guess we are talking about venetian plaster/ Tadelak but I am not sure if this finish would be strong enough for a floor finish ?

Paul
- CommentAuthorfostertom
- CommentTimeJan 25th 2009
Instead of screed, how about very thick tiles - you can make your own 1ft sq x 2.5"thk out of cob - different colour clays from black to red to yellow to silver, swiss roll patterns, encaustics, all sorts. Air dried, then lots of linseed applied. Lay in clay mortar- nice and rough and rustic, environmental impact zero, except the petrochemicals (aka 80% of most food) the tile maker eats. The cob specialists will tell you how.
- CommentAuthorselly
- CommentTimeJan 25th 2009
I respect your views but buying slates from china/ brazil is not necessarily as environmentally unfriendly as you may think.

i mean they can harvest slates quite efficently and shipping can be relatively low in carbon footprint.

Did you know for example in terms of food miles and co2 driving a little bit of shopping home from the supermarket is far worse than anything else. iygwim.
- CommentAuthorbot de paille
- CommentTimeJan 25th 2009
Im talking about mixing sand, gravel and lime the same as you would a cement screed and putting it down 5cm thick then polishing it by hand or machine.
- CommentAuthorwomblepaul
- CommentTimeJan 26th 2009
fostertom - I really like this idea and will look into it. Though I still have to pour a concrete or lime screed to cover the UFH pipes that I have already fixed to my 100 mm of insulation. If I pour a self levelling screed at 50mm to cover the pipes I only have 25mm left to finished floor height. If I put a standard 65mm screed down I am only left with 10mm.

bot de paille - I will look into this further thank you.
- CommentAuthorcookie
- CommentTimeJan 26th 2009
How thick a screed are you looking to put down?
What is the composition of the floor as it stands? i.e. orginal floor, insulation?
What is the maximum and minimum depths do you have to work to?
Do you know who suppliers concrete to your local area? Cemex, La Farge, Tarmac etc?

I can give you some pointers from there if you like.

Cookie
- CommentAuthorwomblepaul
- CommentTimeJan 26th 2009
cookie - The screed will be 50mm if I put a flowing screed down. this leaves me 25mm to finish floor, unless I am going to polish the concrete/lime then I can go thicker (25mm thicker)

If I use a traditonal dry mix I will put down 65mm and have 10mm left to finish the floor.

Floor is hardcore, 140mm concrete slab, 100 kingspan floorboard with UFH pipes clipped to it

Max depths inc screed is 75mm, Triple glazed french doors already fitted determines floor height

Cemex are local suppliers. pointers would be good. Do you have experience of polishing the concrete ?
- CommentAuthorcookie
- CommentTimeJan 26th 2009
Firstly I'm not a concrete installer and if someone knows better feel free to correct me :o)

You never mentioned DPM? (damp proof membrane) have you installed one & where?
What insulation are you using around the perimeter of the wall / expansion foam?
How close can you get a concrete wagon to the point you need it? Dry screed will need to be poured on plastic sheeting outside, wet concrete can be pumped into place but at a higher price.

The semi dry / dry mix screeds are usually laid on top of insulation by marking the height around the perimeter wall using a level (laser level hung from ceiling is ideal) then metal runners laid to the width of the screed layers tamp/float 3 to 5 metres. Then he works his way out of the room. These screeds take several days to go off and can’t be walked on until then. I’ve never heard of polishing dry/semi dry screed as you go along (but that doesn’t mean it can’t be done or post curing)

I would never recommend an amateur or avid DIY’er to try this! Not if it’s the finished floor although the good thing is because it’s so dry and concrete cures by hydration (less water usually the longer you have to work with it but this depends on various things) If your putting a surface on top then you can take out some of the blemishes if it’s the final finish only a few millimetres will be noticeable. Most screeds of this type you have all day to work with it before it goes off, professional teams are at least 2 people, more if you got longer to barrow the screed.

When you pour a wet concrete slab, you can polish it mechanically (powerfloat) I’ve never seen it done by hand other then ‘troweling’ off the edges / corners for an area this size. Laying wet concrete is physically very demanding, you have 2 to 3 of hours max to work with the concrete from the time its batched to getting it somewhere level, then when its cured enough you start the powerfloating which could take another 8 hours, if it goes wrong removing it is a disaster! I’ve used this technique 100’s of times if you want more info I’ll give you some pointers

(I’ve never done this on one of my sites) If your looking to grind the surface of a cured concrete and buff it / seal it then you should consider exposed aggregate concrete, you add a nice stone, coloured glass and a dye then basically powerfloat it off as normal then you grind it down to give like a granite worktop effect, one day I’ll have a go this myself but I don’t know the exact process for this, I think I saw this on Grand Designs once and liked it. Have a look at this website for some technical bumf on concrete http://www.pavingexpert.com/

Self compacting concrete / screeds (self levelling) by far the easiest to lay your self if you local supplier covers your area. Very strait forward, but the area you are pouring into must be watertight. Now I’ve never poured this directly onto insulation (the insulation is usually under the concrete slab (with a screed poured on top for finish) or under the DMP to hold it down. If the screed can seep under the insulation you run the risk of it lifting / floating up, and it will!

Concrete does crack, there is several types of cracks and there are several measures to reduce these, but whichever screed / concrete you use, you better not turn on your underfloor heating for 8 weeks and then only at a couple of degrees warmer then the floor temperature and build it up over a period of weeks, there is calculations out there for concrete drying times. Plastic, wet hessian, or a chemical curing agent applied to the surface will reduce the risk of cracking, your trying to reduce the speed of which water escapes the concrete not speed it up. Self induced crack lines at door opens are the best bet (you cut them in or put a nice smooth joint there so it doesn’t crack itself.

I'll have a think, but if you can answer me the couple of points at the top I'll rabbit on a bit more :o)

Cookie
- CommentAuthormarktime
- CommentTimeJan 26th 2009
Slate is used as ballast on return trips so its contribution is negligible.
- CommentAuthorhowdytom
- CommentTimeJan 26th 2009
Womblepaul,

Do a search for natural earth floors , as fostertom says , polished with linseed, they look fantastic, can't see why you would need concrete on top of the pipes, earth would work just as well, better still should you get any damage its easily repaired
- CommentAuthorfostertom
- CommentTimeJan 26th 2009
howdytom, what's this - in effect cob screed? Of course it would shrink and crack to hell on drying, so would have to scribed into 1ft sq faux-tiles and the shrink-joints grouted, like real tiles. But even so I'd think you'd get additional cracking over the pipes? If these problems are soluble, then great - how revolutionary!
- CommentAuthoradwindrum
- CommentTimeJan 27th 2009
Wouldnt the cob insulate like the air filled concrete?
- CommentAuthorhowdytom
- CommentTimeJan 27th 2009
I wasn't saying its easy or wouldn't crack, but take a look at the link below. I do like fostertoms idea, cob may insulate it a bit though.

As they say "open your mind, before you make it up"

www.designcoalition.org/features/natural/earthflr.htm
- CommentAuthorfostertom
- CommentTimeJan 27th 2009
Cob isn't insulative. or hardly more so than any earth/rock/concrete (non aerated) material.
- CommentAuthorfostertom
- CommentTimeJan 27th 2009
Posted By: howdytomwww.designcoalition.org/features/natural/earthflr.htm
a great, and proven technique to hold in store - thanks
- CommentAuthorRachel
- CommentTimeJan 27th 2009
not so, fostertom. My earth floor on top of UFH never cracked if mixed and rammed and polished properly. 3 sand to 1 clay with bit of manure, chopped straw looks nice too then polish with plastic and finish w/ linseed.
- CommentAuthorbot de paille
- CommentTimeJan 27th 2009
I think the key with earthen floors is that they should be very well compacted, which will reduce the air content as they dry, reducing the cracking and making them more dense and less insulative.
- CommentAuthortomaspain
- CommentTimeJan 27th 2009
This all sounds fantastic! i´m in exactly the same position, UFH layed and waiting for me to make a decision on the screed. i´d opted for a polished concrete floor but so far havn´t found a contractor to guarantee a crack free result. what i´ve found out so far is that self leveling concrete is a weaker material and because its so wet to start with will be guaranteed to crack. (according to one local contractor who only pours self leveling concrete) the traditional concrete mix is much stronger and will crack less. in both cases spacers in doorways or in areas over 25m2 will greatly reduce cracking.
the final area is the finish or sealant. Epoxy or polyurethane? They both give off a nasty gas according most eco build sites i´ve seen. some american and australian polished concrete sites suggest a water based silicate which acts as both sealant and also hardens the first few mm. wonderful. back to my contractor here in north spain and he says absolutely not, the silicate, if in contact with water after its been applied will start to eat the concrete away, much better to use some sort of coloured powder thrown on at the last minute. finally looked into micro cement 1 - 2 mm cement resin coating, but its very expensive even if they sell the product to you 25 per m2. a trained applier charges €70 per m2 here.
earth floors. i like the sound of but aren´t they very soft?
cannabric.com a company in granada swears by polished lime screed, basically stucco, the photos were vibrant but sorry i can´t find them now. she also mentioned a stucco dance floor in madrid from the 50´s still in very good shape. this is still a possibility but again she was unsure of the effects of UFH on the stucco.
thats all i´ve come up with so far...not many solutions
- CommentAuthorwomblepaul
- CommentTimeJan 28th 2009
Very interesting. I really like the idea of the cob floor. I would like to know how to lat this what heights etc and can I use over 100mm of insulation, Rachel could you enlighten me ?

Mart Time: I wasn't aware that the slates are coming back as ballast. Out of interest what do we export in the first place ?

Cookie: DPM is below 140mm slab, I have edge insulation in place. I have looked at the two types of screed and wasnt going to do this my self. I did pour the slab and that was good but the screeding I would leave to a contractor. I am getting quotes of £1500 for dry mix finished and approx £2000 for the poured screed. This doesn't get me my floor finish though.

I was going to grind the top of the screed and then polish it. But as you say there needs to be aggregate in the mix as its the aggregrate that gets polished. Because I am pouring the screed over UFH pipes, concrete is not ideal...

I have also looked into hiring the grinding machine and various sanding pads and it looks about £900 for the week. Then I will need to dedicate 8 hours a day for 5 days to get a good finish. There is also the question of how it will turn out.The cost to get a contractor to do the job is much to high for me.

Its a shame as I think if you are going to use concrete this is a really great way of saving on the the extra materials needed to get a floor finish.

Tomaspain :I know very little about resin finishes to concrete but I an guessing they are probably super bad on ecological grounds?

So I am not sure how to progress. I would love to do a polished lime or cob floor but think my time scale (floor is covered in UFH and resady to go. And also I would want to talk to someone who could give me a few tips before I start doing either of these.

Hmm more decisions. Working on the roof instead as I can't work on the ground floor !

Has anyone done a lime floor with UFH?
- CommentAuthorRachel
- CommentTimeJan 28th 2009
I think I explain the floor laying process on my website www.quietearth.org.uk 'the story so far' and I also have apolished limecrete floor with natural earth pigment in it. The earth floor is 2" thick on top of limecrete with 200 insulation (leca) below. It's all quite easy really.
- CommentAuthorwww.milesSampson.com
- CommentTimeJan 29th 2009
OK, there are a few things to consider here, 1st there are two distinct parts.
1. Polishing: You can polish any concrete floor and if it is done well any concrete will look good.
2. Your aggregate: When you polish any concrete the aggregate gets exposed, so this becomes one of the most important elements.

POLISHING
Polishing is not that difficult, but it is very time consuming, and this is generally what makes it expensive. For 100m.sq. you will need about 10 full days of just polishing, depending on the complexity of the walls and room shapes. To polish a floor well you need to start with a course diamond head on the grinder, and then keep selecting finer heads. Then as you get close to the last head you apply a surface harder to the concrete, which toughens up the concrete and helps give it a glossy look. That is the easy bit. You then have to go around all the edges of all the rooms with diamond heads attached to an angle grinder doing the same. This is the pain in the back work. To do it yourself I have looked into hiring the machines and that is not a problem, but hiring a good selection of heads is the difficult part. Plant hire shops do not like to hire out the heads because they are expensive and can get damaged easily. In the current economic climate you can probably get a very good deal from an experienced floor polisher. In Ireland you are looking at between €30-€60/m.sq. for the floor to be polished.

CONCRETE AND AGGREGATE
The gravel or sand or chips that you use as your aggregate are what will give the polished floor its character, so put plenty of thought into selecting them. I choose to use recycled glass (because it is more sustainable and had a nice colour). I was able to get the crushed glass at two grades, 5mm chips and fine sand, so 100% of the aggregate was recycled. I choose green glass, but it had a flavour of all colours especially bits of red plastic from bottle tops (which I actually like). The cement I choose to use was GGBS which is blast slag, a by-product of the steel industry, so has lower embodied energy. This is lighter in colour than portland cement, but takes longer to set. In the end I used 50% GGBS cement and 50% white portland cement to make the floor look bright. The maximum amount of GGBS you can use is 70%, but because it slows down the drying process I had to strike a balance, as I needed the floor polished relatively soon. Using the GGBS has another advantage that the concrete cures slower it, therefore cracks less. I put UFH in the screed which is 75mm thick. 75mm is the optimum thickness, because if it is thicker than your UFH is less responsive, but if it was thinner it would not be strong enough. I used glass fibre reinforcement in the screed, which seems to have done the trick. The only cracks are at doors between room, and these can be hidden with saddle boards. Mixing and laying the screed was the most difficult part. Mixing it on-site in a small mixer was not an option, because you need to keep consistency between the batches. We hired a cement truck, droved it to the place to get the crushed glass and they added in the cement, then we drove it back and added the glass reinforcement. It had to be wheelbarrow by hand into the rooms and levelled by hand with trowels. After it had been levelled and worked we sprinkled more crushed glass over it and gave it one last towelling. This was done because when the concrete is worked the cement tends to come to the top and the aggregate sink to the bottom.

The construction of the house was filmed and here is a link to the section on the polished concrete floor http://es.youtube.com/user/ecologicalarchitect

This is an outline of what was included, I have omitted phone numbers of suppliers, but if you email me I will provide them.
Mix:
A mortar of 4 parts aggregate to 1 part cement was used for the floor.
Thickness:
It was laid 75mm thick over under floor heating pipes.
Ingredients:
1. The cement consisted of 30% GGBS and 70% white Portland cement
2. The aggregate consisted of crushed recycled glass in two grades. 50% course 5-
6mm, 50% fine 2-3mm. It was primarily green bottles that were used.
3. A polyaramid reinforcement was used, Fibreflex. It was mixed at a rate of 1kg
Fibreflex for every 1m³ of mortor
Finish:
It was polished with a diamond grinder using various grades.
Suppliers and Contractors:
1. Recycled crushed glass was supplied by Jackie Whelan at
http://glassrecycling.ie/ He was able to mix the ingredients for us.
2. GGBS cement was supplies by ecoCem. www.ecocem.ie
3. I use local specialists to lay the concrete floor.
4. The polishing of the floor was done by a floor polishing specialist. Call Ian O'Connell
from TopCoat http://www.topcoatsystems.com
5. The glass fibre reinforcement that I used was supplied by Stoneware Potteries in
Cork.
- CommentAuthoradwindrum
- CommentTimeJan 29th 2009
A key point to learn here is planning ahead.

Why arent builders planning EVERY detail in advance?

Marktime - Surely you are talking 200 years ago with sail ships. I cant see modern day tankers wasting time in port waiting for the ballast, its all containers these days.

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General: polished concrete flooring ?