I think cement dries quicker than that. We had our kitchen done 5.5 years ago and we certainly didn't wait more than a day. We had tiles put in but the floor needed to be made level with cement. We are hopefully having parquet put in in a couple of months and the floors will all need levelling with cement. We had a quote for this last summer and the guy (from a local big department store) didn't mention more than one day's work. We have changed our minds about which rooms need doing so will need a new quote etc.
DH says - yes you do have to let it dry out before putting a surface on it otherwise you seal in the moisture. And it does takes week for cement/concrete to dry out.
But (my thoughts) presumably they lay the cement before they build the walls - so in the time it takes to build the walls and roof, and then build the internal structures, tehn plaster etc - it will be drying out all that time. THEN you put the wooden surface on - probably that is weeks between the two.
What did the builder who quote for in terms of time? Did he break it down into phases ? When are you expecting to be using the extension ?
Apology for misleading earlier message. Just checked with DH and what we used in our kitchen was self-levelling flooring compound, which is a fast-drying material (a matter of hours), but not real cement. Proper, building cement does take ages to dry and settle.
We finished laying 10cm of concrete on our floors in October and by December it still had too much damp in it to lay the wooden floor....the floor people come every so often to take a reading and will only lay it when they are satisfied that it is truly dry (obviously it looks and feels dry to us, but they say if the reading is too high the floor will buckle and be damaged!) So it looks like it will be able to be laid end Feb...rough rule was 1mm per day, so we had 100mm, so three months...(and we had an accelerator in the concrete).
polly28 we are currently having an extension built and the concrete floor was the first thing they did - they have also built a scaffolding 'shell' with a plastic wrap 'roof' and 'walls' so even if it rains the floor stays dry - might be worth mentioning to builders? We can't have wooden floors as you need to raise the height of the floor by 3" and our ceilings are already ridiculously low (cottage)