Extensions - how long does the concrete take to dry and be safe to walk on?

[said]

Thanks. The bit that fills the floor area.

Depends, but it should be fine the next day to walk on. It won't be fully dry for about a month though.

A month? Surely you don't have to wait a month to put a kitchen in etc?

No, but it does take a month until it's fully cured - until then any extreme fluctuations in temperature can cause cracks.

I personally won't put tiles on concrete until it's been a month (I like to use reclaimed tiles and do not appreciate breakages).

Thanks for info

I was told a mm a day until 40 mms and then half a mm a day [this is with underfloor heating].My builder refused to let me do anything until my floor reached its allotted curing time span.The concrete floor company also said the same thing [as i checked!].

The previous replies are correct; the concrete will be firm enough to walk on after only a day or so and most of the building and fitting work can continue normally after that. A lot of water is released during curing and you should leave windows ajar to minimise condensation.

The difficulty comes when you want to lay an impervious floor covering like vinyl or linoleum. The builder should test the concrete with an hydrometer and only once the RH (Relative Humidity) reading has fallen below 75% can flooring be laid.

Good luck with the project.

Thanks both. Likely to be nearly 3 weeks before kitchen goes in (at earliest) so flooring will be quite a while.