New concrete slab - how long before flooring?

ezman

Hi all,

Have you had an extension which involved a concrete slab?
How long did you wait to put flooring down over it?

My builders, for whatever reason, have waited till I have the walls, the roof, even the windows in many parts, but still no slab!

The slab still has to be put in and at the moment it's too cold.

I was clueless (until I read the flooring instructions) that this was a big issue and never raised it as a concern. 150mm slab seems, in ideal conditions, to mean 150 days or more of waiting before the concrete is considered dry enough to lay flooring on.

Whoever I get to do the flooring, I'll ensure they use a moisture meter, but generally what are people's experiences of the wait?
Some magazines show the slab being laid and then 8weeks later they're putting the flooring in? Is this just nonsense?

Is there any methods/alternatives that could be used to reduce this time? Is there a precast concrete solution!?

Could I at least install the kitchen (perhaps on raised plinths) or does this need to wait as well?

Sorry for all the questions, thanks for any help, really appreciate it.

zaax

Concrete has its most rapid strength gain over the first 7 days and is considered to be cured and near full strength in 28 days although the process of strength gain can virtually go on for ever.

Water has nothing to do with the 'setting' of concrete it cures.

wallbash

Perhaps 'slab' is now the wrong word.
I picture the slab first, then the walls are built on it.
You have an extension with standard wall foundations. Then the floor is created ( concrete plus screed ??)
The 'slab' would be very thick, while the concrete floor a few inches.
But yes its going to take time to ( nearly as zaax) to cure.
Read somewhere that the concrete in the Hoover Dam is still getting harder!

Maybe you should talk to your builders?
But any work this week ( weather wise ) was a bonus.

manda1205

I'm pretty sure it's a week to dry for every 10mm of screed. I think ours was 120mm and we waited 3 months. We had our kitchen fitted and table in. We just put down some off cuts of carpet in areas we would stand more often. We then had our tiles laid.

ezman

Hi, it's 65mm sand and cement screed on insulation (70mm) on 150mm concrete slab.

wallbash

Doing a little (google ) search came up with

A rule of thumb for new concrete is one month per inch or one day per one millimetre drying time.

But there must be a variation depending on conditions, this time of year allow longer.
I think manda has the right idea.

ezman

wallbash wrote: »

Doing a little (google ) search came up with

A rule of thumb for new concrete is one month per inch or one day per one millimetre drying time.

But there must be a variation depending on conditions, this time of year allow longer.
I think manda has the right idea.

Thanks Wallbash, I've seen that but wondered if people actually waited that long in practice.
I wonder why it has to be 150mm slab, will speak to architect tomorrow, 120mm like manda would bring things forward 30 days

dampdaveski

Ez,
Speak to your architect, but basically you need to leave it as long as you possibly can, if you still get readings (an electrical resistance moisture meter is NOT the tool to use) you can consider laying a surface applied liquid Damp Proof Membrane, seek advice from the manufacturer of the flooring you intend to use

wallbash

ezman wrote: »

Thanks Wallbash, I've seen that but wondered if people actually waited that long in practice.
I wonder why it has to be 150mm slab, will speak to architect tomorrow, 120mm like manda would bring things forward 30 days

The depth of the concrete will depend on a number of things and will have been calculated, asking for a thinner slab is unlikely to be met with enthusiasm. Most people go with intended depth , have patience and get on with the rest of the build. You can still go ahead with lots in your new place, just not a covering on the floor. You are talking about another month, when I did a whole ground floor, I waited three months before I started choosing carpets.

to sum up .......... patience

manda1205

It really isn't much hassel to wait. Once you've swept up and installed kitchen it's then just like having a hard floor. I used to hoover ours. With all the conensation you get to begin with (the walls still drying out etc) it really is worth waiting.

ezman

manda1205 wrote: »

It really isn't much hassel to wait. Once you've swept up and installed kitchen it's then just like having a hard floor. I used to hoover ours. With all the conensation you get to begin with (the walls still drying out etc) it really is worth waiting.

Big Thanks Manda, how long did you wait to install kitchen? Did the moisture affect the cabinets? I'm assuming you just floored around the units (originally I wanted to floor the whole lot but looks like that will not be possible, no biggie).