Floor screed drying times

[andy183]

Hi, My builder opted to have a liquid calcium sulphate floor screed.

We have radiators in the building and the technical specification says we can "force dry it" after 7 days of being laid.

The tech sheet states that in ideal drying conditions Screed dries at a rate of 1mm per day up to a depth of 40mm and then at a rate of ½ mm per
day for any additional depth. According to my builder we have at the thickest point 65mm of screed. This means we will need to wait 3 months for the floor to fully dry out.

4 weeks have now passed and my builder is eager to start laying the tiles and wood floor. I am eager to get the work done, but am worried that it might all rot if the floor hasn't been allowed to cure sufficently.

The floor itself feels dry to the back of my hand. I have done a low tech test to see if I get any water condensation by putting a sheet of DPM on the floor. After a few days the DPM was still dry with no water condensation.

I am getting my carpet fitter to come out and test the floor with a damp meter to try and get a better idea of how dry/wet the floor is.

Any advice how to proceed? or what I should be checking for?

I am planning on putting down tiles, and a woodfloor with underlay with a built in DPM.

 

[regsmyth]

If the screed isn't fully dry, then the moisture might cause the wood floor to swell, possibly bulge upwards. It won't rot away.

However, it would seem to be dry enough if your dpm didn't trap any moisture. Your carpet layers meter should give you a confirmation. But either way, it's your builders responsibility really - if he decides to go ahead, and it goes wrong - his problem. If you tell him to go ahead, against his advice, your problem. Get it in writing?

 

[andy183]

The carpet fitter turned up without the moisture meter, so I'm thinking of just getting a device myself and testing it at different points and taking a average.

Would this be okay in producing something accurate?

http://www.amazon.co.uk/gp/product/B0036PXME2?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

 

[ree]

Why was this method/material chosen?

How thick is the screed?

What is the sub-base and does it have a membrane?

Besides the rads, Is there any UFH in place?

 

[andy183]

The choice was the builder's. I will ask him why on monday.

Screed is 65mm at it's thickest.

Sub-base is concrete slab. A Polythene Sheet was laid on top of the concrete before the screed was laid. The concrete has it's own DPM further down.

No UFH.

 

[ree]

One condition: is the screed surface clean of latience, and is it almost pale white? Otherwise you should be good to go.

 

[andy183]

One condition: is the screed surface clean of latience, and is it almost pale white? Otherwise you should be good to go.

It is pale white and shiny in areas. It hasn't been sanded with any sort of machine.

Can you tell me what Latience looks like?

 

[ree]

A sort of brittle scum, sometimes slightly discoloured.

Lightly tap any suspect surface with an off-cut of wood, if latience is there it will disintegrate.

 

[andy183]

A sort of brittle scum, sometimes slightly discoloured.

Lightly tap any suspect surface with an off-cut of wood, if latience is there it will disintegrate.

Nothing disintegrates if i tap it with a peice of wood.

However i do have a layer on top which is dusty. The floor is also not one uniform colour but discoloured in placed. It seems like if i do rub the surface hard it comes away. It isn't solid like a concrete floor. Not sure if this is the same as Latience.

Some pictures of the floor which might help:

http://s1242.photobucket.com/user/azt5150/library/?sort=3&page=1

Many thanks for taking the time to help.

 

[ree]

You should be fine.

I'm guessing that this screed was poured by the builder and not specialist sub-contractors - i say this because the surface, allowing for the pics, is not quite as the professionals would finish it. But you should be good for tile and wood.

Give the surface a good vacuuming, and prime prior to spreading the tile adhesive.

 

[andy183]

It was actually fitted by specialist subcontractors who do nothing but liquid screed floors in the midlands. I guess from your reply you can't see any noticable Latience?

I've tested the floor with a moisture meter that I got off amazon and the highest level i could get was 35% (hallway). Most of the floor is in the 15% to 18% range.

 

[ree]

This material and method, done by specialists will leave a baby's bum smooth surface fit to lay sheet vinyl on. Your pics dont show that standard of surface - if anything your surface has been over trowelled. But nothing to stop you getting on with the next steps. As above, you are good to go.

 

[andy183]

Many thanks for all your advice.