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[Tony H]

Hi all a friend has just had a new extension to her kitchen built that has a concrete floor. She has just had a flooring company come out to quote to lay a vinyl floor, the chap states that because it is fresh concrete she will have to wait four months before the vinyl can be laid unless she forks out for an expensive damp proof membrane between the concrete and the vinyl. Any input would be appreciated as four months seem quite a long time to me to allow the floor to dry out 
TIA for any replies
Tony

[hercules]

a quick peep on google states if laying on a new concrete floor it can take up to six months to dry out completely 

[2boxerdogs]

Yep, can vouch for this bought a new house in 1979 in South Croydon vinyl floor in kitchen had been laid on concrete which had not dried out, resulting in wet winyl all had to be removed & done correctly.

[Marks DTM Calib]

Yep and a vapour barrier is no good as ......it will never dry out (remains damp under it, all it does is protect the floor a bit!).

Its typically considered to be 1 day for every mm of thickness.

How do I know? I have contractors in putting down 75mm of screed today!

[Tony H]

Hmmm! taking in to concideration Marks post is the answer to leave the concrete exposed until it is dry? as that will leave the project unfinished for months. Could the answer be to carry on with the kitchen fitting etc. and leave the floor as the last job a few months down the line?

[tunnie]

Having just had some plastering done, that took a week to dry. So can easily see concrete taking months!

[2boxerdogs]

Have spoken to my son in law who is a builder, he says they allow a day for each mm of concrete depth, there is a meter that can measure the amount of damp in a new floor.

[Andy H]

Yep and a vapour barrier is no good as ......it will never dry out (remains damp under it, all it does is protect the floor a bit!).

Its typically considered to be 1 day for every mm of thickness.

How do I know? I have contractors in putting down 75mm of screed today!

I had 75mm of screed laid in my kitchen & extension in December 2014. We needed to use the space so we bought some felt backed carpet and laid that directly on the screed as protection.

After 5 months I believe it was pretty much dry. (but it took me until last month (February 2016) to finally get round to laying 40 square metres of floor tiles

[Andy B]

.....

After 5 months I believe it was pretty much dry. (but it took me until last month (February 2016) to finally get round to laying 40 square metres of floor tiles

You just can't rush a good job! 

[Sir Tigger KC]

Can you speed up the drying process with a dehumidifier? 

[Andy H]

Can you speed up the drying process with a dehumidifier? 

Not really

It takes a long time for the moisture to migrate from the core to the surface. Screed shrinks as it dries, if the surface is drier than the core then it will crack (particularly when it has not reached anywhere like full strength) . Also if you dry the surface quickly then it will never reach full strength and crumbles.