Drying of screed

[Ashandiamo]

Just wondered if anyone can offer any advice regarding our floor screed and it apparently not drying.

The screed, which I believe is about 60mm anhydride, although I can’t lay my hand on the exact spec at this time, was laid in October 2018. The contractor eventually returned around January and buffed it to remove the laitance film. There was a delay with the UFH and it eventually went on at the start of February this year.

The majority of the ground floor will  be LVT flooring. The flooring contractor came out around the start of March and the RH readings, which were taken with a digital Hygrometer were off the scale. He then had them buffed once again with a copper pad in the hope this would help. He returned at the start of April and the readings were both 90% RH. Since then we’ve cranked the UFH heating right up, being carefully not to crack the slab, and had all the doors and windows open but it seems it’s made no difference as the Hygrometer’s are back down. They are due to be lifted tomorrow afternoon and are already reading 86% and I expect they’ll go higher. It seems all the heat and ventilation has made no difference and it’s starting to feel like we’ve a house which isn’t fit for purpose.

About to enter ‘discussions’ with the contractor that laid the anhydride screed although, call me cynical, but I expect the response to be - we’ve never had this before!

Can anyone please shed light on where we go from here. We’ve built our dream home and although it’s almost finished we have no prospect of moving in as we can’t get flooring down. Has anyone used the liquid DPM products or membranes to get round a similar problem and if so has it been successful?

Many thanks.

[ToughButterCup]

Hmmm, basics first - have the hygrometers been tested and calibrated? When? 

[Ian]

As a first step I'd ask your flooring contractor if he can organise for a calcium carbide test to be done so that you can compare the results with the hygrometer test results. It's possible that you've been getting false positive readings from the hygrometer testing and carrying out a calcium carbide test will let you know if there's a problem or not with the testing you've done so far.

Calcium carbide testing is quick but it involves taking a small sample of the screed which is weighed and put into a testing vessel and mixed with calcium carbide powder - the results of the chemical reaction allow an exact measure of moisture content to be taken and is more reliable than hygrometer testing.

Edited May 2, 2019 by Ian

[Ashandiamo]

Good point about the meters being calibrated, will need to confirm that.

Ian, thanks for the info regarding the calcium carbide test, never knew about that being an option so definitely one I’ll progress.

Will post an update with the outcome once I know what it is.

Many thanks 

[Ashandiamo]

Just an update on the floor saga. The company that’s laying the finished flooring removed the hygrometers which were reading 83% although the highest they’d been were 87 and 88%. They are still saying it’s too wet however the company that laid the screed also visited yesterday and used a Tramex Encounter 4 moisture tester. They took numerous readings which all gave readings of less than 2%. Not sure how it works but the two systems must work on different scales. 

So now I’ve got the Screeding company insistent it’s dry for LVT flooring and the finished flooring company saying it’s not - aghhh! ?

Will need to try and progress the calcium carbide test somehow and also, if the screeding company are so confident of their figures, will they accept liability if we have issues with flooring after it’s laid, if they will that will definitely need to be in writing. ?

Ahhh - the saga continues.

thanks again.

[Declan52]

Did you try covering a small section with some polythene and see if it starts to sweat. A dry floor won't.

[scottishjohn]

sounds dangerous to me --no way can i see screed company taking responsibility for tiles coming loose later down the line --they will say it was the way they were laid

 

you need to get know its correct now before going further

[Dunny1234]

Interesting post. I’m about to hire a sander to do my screed. It’s been down for over 100 days, so slightly concerned I’m really late to the latience removal party. Also, what the best way to do corners, and more detailed areas? Is there a disc I can pop on a angle grinder. Thanks 

[Caroline]

I have an issue. Our screed was laid in Nov and latex/stickdown LVT laid two months later. UFH wasn’t turned on.

 

Couple of months later approx 15sqm (out of nearly 200sqm) started to lift. Floorlayers removed lifted areas and found moisture on the back of the LVT, floor looked dry and hand held moisture meter said 35% moisture.

Flooring people then used a larger meter that sticks to floor and readings over a week went from 76-83% too high to relay LVT.

 

The slab/screed which had a drying accelerant in it should have been dry in 2 months. Newbuild bungalow.

 

we are worried if floor is reading up

to 83% in lifted areas what about areas that seem fine (LVT flat and appears fine)

 

I know lots in here don’t like LVT but I have it now so not much I can do.

 

Also flooring company only used small hand held reader before laying the LVT, this reader showed it was dry enough to

lay originally but obviously the hand held device wasn’t accurate.

 

Also who is responsible for the cost of replacing the LVT?

 

Any advice is appreciated.

 

Thank you, as always.

[Nickfromwales]

28 minutes ago, Caroline said:

I have an issue. Our screed was laid in Nov and latex/stickdown LVT laid two months later. UFH wasn’t turned on.

 

Couple of months later approx 15sqm (out of nearly 200sqm) started to lift. Floorlayers removed lifted areas and found moisture on the back of the LVT, floor looked dry and hand held moisture meter said 35% moisture.

Flooring people then used a larger meter that sticks to floor and readings over a week went from 76-83% too high to relay LVT.

 

The slab/screed which had a drying accelerant in it should have been try in 2 months. Newbuild bungalow.

 

we are worried if floor is reading up

to 83% in lifted areas what about areas that seem fine (LVT flat and apprears fine)

 

I know lots in here don’t like LVT but I have it now so not much I can do.

 

Also flooring company only used small hand held reader before laying the LVT, this reader showed it was dry enough to

lay originally but obviously the hand held device wasn’t accurate.

 

Also who is responsible for the cost of replacing the LVT?

 

Any advice is appreciated.

 

Thank you, as always.

The fitters should be using (should have used) industry recognised practices for measuring moisture, not a £20 B&Q tester. 
 

Likelihood is that they’d never be employed if they tell every client that the slab isn’t dry enough to lay……so maybe an incentive exists to do the most rudimentary test possible.  

[saveasteading]

7 hours ago, Caroline said:

should have been dry in 2 months

Yes it should have been, unless it got wet some other way.

How thick is the screed and what is under it?

 

[SteamyTea]

4 hours ago, Caroline said:

UFH wasn’t turned on.

Is that leaking by any chance?