Advice on a concrete floor and finishing

onionsa · 17 Oct 2019

I need to put a concrete floor in my workshop which is brick walled. It’s roughly 2.5m x 2.5m.

Would I need to put some wood beams down the sides to act as a form and a tamping level or is this not required?

I’d also like the finish of the floor to be smooth. Could I manage this with a hand tool as I go or do I need to get a big float on it?

Thanks in advance.

noseall · 18 Oct 2019

There is an art to finishing concrete successfully. I have been in the trade since Noah built his Ark and I am still rubbish at getting a nice ~~right~~ tight finish on conc.
The trick is to ~~ramp~~ tamp it level the leave it until it is firm enough to walk on but still not set. Then work like fury with a float and trowel trying to get a finish.

This post has been edited due to auto-correct shinnanigans

23vc · 18 Oct 2019

+1
Also with the “big float”, my understanding is that’s more for when the conc is still wet, to level it. When it’ll take your weight, it’s hand trowel time
I’ve done a couple now, one of which I used a big blue type float with, other just left it tamped, did the plastering trowel and polyfloat thing later in the day, no discernible difference between the two

^woody^ · 18 Oct 2019

For a finished surface, you need more fines (sand and fine gravel) rather than large stones, and less water - or wait for hours until its dried off.

TBH, I would not worry or mess about too much. Trowel it as good as damn it, and then self level or use neat cement in any imperfections, and then use a good floor paint.

onionsa · 18 Oct 2019

Thanks for the info guys. Just what I needed to hear.

Question I still have is do I put beams down the side as a form to tamp against or just fill it wall to wall and eye ball it?

bobasd · 18 Oct 2019

No, no need for "beams". and no need for a "big float".

mark the finished concrete surface required on the wall - this will usually be the doorway threshold level.
and simply pour to that marked height, and then do as others have suggested above.
rough levelling off with a straight edge and float, and finishing with a steel trowel will be straightforward in that small area.
for an almost polished finish you could go over it using kneeler boards - but no worries, you'll soon get the hang of it,
long before the stuff sets up.

all the above thread presumes you've got everything prepared, and no DPM or insulation is involved?

23vc · 18 Oct 2019

bobasd said:
simply pour to that marked height, and then do as others have suggested above.
rough levelling off with a straight edge and float

so you don’t tamp it to anything then, does that still give a level surface? Thought about doing it that way but always tamped to the brickwork or a guide timber screwed to the wall.

bobasd · 18 Oct 2019

yes, obviously you can work to fixed levels but for what it is you can straighten it out as its poured - get close - and finish off as above.
keep a barrow of stuff in reserve

thing is, some, maybe lots of, people are scared of concrete - they shouldn't be.
good prep and a few pairs of hands and its a case of learning as you go on such a small enclosed area.
its only unforgiving if your out of your depth (large area, complicated footprint) lack preparation, and dont stay with it.

onionsa · 19 Oct 2019

I’ll be doing it alone so will only have myself to blame if it goes wrong but this stuff seems to be pretty workable. Not got to support a sky scraper, just somewhere for me to stand while I work.

I do have a DPM to go in, does that complicate things?

bobasd · 19 Oct 2019

with a DPM you could revert to your original idea of fixing "beams" (or fixed levels) set just above benchmark height for tamping and screeding off.
these "beams" would also pin the edges of the DPM to flap up the walls above finished floor level.

onionsa · 22 Oct 2019

Ok will have a think about if I use the beams or not. Seems simpler without as long as I can pin the DPM to stop it folding over and then trim it back once everything is dried.

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Advice on a concrete floor and finishing

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