laying smooth concrete floor

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I need to finish the foundations for my dwarf-walled Victorian conservatory (measures approx 2.5m x 2.5m) by laying 100mm of concrete and would like some advice as I want as smooth a finish as I can get. I have already put down 150mm hardcore, 30mm sand blinding, a layer of visqueen, insulation and now just need to get the concrete sorted.

For various reasons the conservatory has already been built around the base, which I know wasn’t the best order in which to do things but I’m unsure about how to finish it off as all the walls are already up. Do I still need to use shuttering to contain the concrete? How do I tamp it given the conservatory base is like a hexagon, 2.5m deep and the walls are up so I can’t walk around the outside? What’s the best way of smoothing it off?

I’d really like to get this right first time so would very much appreciate any advice on how to go about doing this! Thanks
 
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The brick walls are the shuttering

You can trowel the concrete with a floating trowel but you wont get a smooth finish. If you want smooth, then you keep the concrete 50mm lower than planned, and then lay a 50mm screed and trowel that
 
If you haven't done it before you'll struggle to get it smooth enough for tiling for example. You could pay a plasterer for the day and he would be able to float it very smooth for you or you could try using a power float but that is also something which a bit of experience is needed.

As woody says for a diy option screeding it yourself is easier to get level and smooth
 
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I was thinking that .... it would be like some sort of conservatory pinball

Kerr-ding, bang, ping ... Bonus 1000 points
 
Thanks for all the replies, if I chose to screed it by having 50mm screed on top of 50mm concrete would either need to be reinforced or are the thicknesses ok?

I'm determined to get done as much of this as I can, I've got some plastering experience and think I would have a better time screeding the floor. How long would I need to let the concrete set before I set about putting the screed down on top?

Cheers again chaps :D
 
50mm of concrete is definately too little better off aiming for 75-100mm concrete

The other option which is less work and if you don't have room is to pour the concrete to 100mm and try floating it by hand, if your not happy with the result buy a bag of self-levelling compound and trowl that over it.

If you have some plastering experience you'll be able to get a pretty good result from the concrete floor floating by hand alone.
 
You can get a good finish on a poured concrete floor, using a float and a trowel. It's a lot of work, and it takes a long time to do, from the initial pour, tamping and screeding it off, waiting a while for any water to come to the top and evaporate, then start finishing. We never used the trowel, until the surface, (that had been floated over a few times), had become firm and creamy. Then we started running the trowel over it,, pulling out around the edges first, then working across the floor. It's a bit like troweling up grano, or even plaster,, you go over the area again and again, until you know it's set. The majority of the large concrete floor areas, were finished using the power float, when the surface could take it, but it can't get into the corners or the awkward places, so that was done by hand. Troweling up concrete is also a great way to break in a new finishing trowel too!
We were never "officially" allowed to flick water onto the surface as we troweled up, even on a warm summers day, because the Clerk of the Works (Mod/PSA), said it made the finished surface brittle,,,, but he wasn't there all the time!!! ;)
 
Been a bit busy lately but this is getting done this weekend, I appreciate the advice so far and just have some last thoughts before I start!

- if I've got brick walls all the way round, what's the best way to make sure it's level? Being liquid-ish will it find its own level?

- When it comes to tamping, can I just give it a good poke with a big length of wood to get rid of any air?

- How long should I leave it before floating it? And what's the best way of doing the far edges without walking all over it?

Thanks again :D
 

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