concrete floor

[woodchopper]

How long does a new concrete floor need to dry out before a new wooden floor be laid on top of it ?

[Clanad]

Here's the test, depending on whether the finished concrete is light colored or dark colored. If light, lay a rubber mat, such as an old car floor mat on the new concrete and weigh it down. If, after 24 ours when you lift it, the concrete underneath is dark colored... it's still too fresh. Alternately, if the fresh floor is dark colored, tape about a 2 foot square piece of heavy plastic to the floor... sealing the edges all around... if after at least 24 hours (48 is better) check to see if there's any condensation collected on the underneath side. If so... it's still to fresh. Moisture meters can be bought to test, but they're a little expensive and seldom used so this method (recommended by my concrete monger) works well...
Be sure, when you do lay the floor to use a good quality moisture barrier. I used at least 6 mil construction grade plastic on top of 15 lb. roofing felt... some friends used high density polystyrene rigid 1 inch insulation boards (the blue kind, at least here in the U.S.) on top of the 6 mil plastic... Best of luck!

[mrpeter]

As a rough guide it takes a day for every 1mm of new concrete or screed. i.e. 2 inches (50mm) takes 50 days.Hope that helps. This is the recommended time when laying laminate flooring on top of new screed.

[buildersmate]

I reckon 3 months - but the above is more scientific and good stuff. it really isn't worth rushing.