Dents in screed appearing under LVT

Could anyone please offer any thoughts on issues I’m having with my new flooring please?

It was fitted last year over Wunda UFH following all the advice and all was fine. Over time we started to notice the tracks of the pipes showing and areas where there were depressions. In the end we lifted some planks and could see the screed had risen where the pipe tracks were. Mapei came out on Wunda’s instruction and the chap couldn’t explain it. We then showed him one area where it appeared the screed over the pipe was too thin. When the technical report arrived, thin screed was all that was mentioned so at this stage they are not taking any responsibility. The issue is getting progressively worse and today I lifted a plank where there was a dip and found what you can see in the picture. This was without question, not like this when the floor was laid. My thought is that something else is going on that has caused the dipping and over time, because the screed is thinner, the pipes are pushing it up as you would expect. Has anyone seen anything like this before? Thanks so much for any help and advice you can give, I’m having a nightmare with this

 

Screed looks like its blown also

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How have you picked that up and what does it actually mean? Thanks for your reply

 

By the cracks in the pictures. If you tap them and they spund hollow its lifted up of whatever is underlneath it

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Defo looks blown, needs section of the actual screed taking out to see further.
What actual screed was used?

 

Is it all over random places or just one particular area??

 

What’s the subfloor ?

 

Apologies, I don’t know the terminology but the floor underneath it all is original concrete from when the house was built with an extension at the back and a small corner extension at the front. The screed was Mapei Ultraplan renovation (recommended and supplied by Wunda) and some black shiny stuff was used in the room where the little extension was but not in the other. The total floor is 76 sq m. The problems are in various places across the whole floor and it is getting progressively worse

 

So they should of put down around 70 bags of screed to cover the system. Its very hard to keep a 10mm coat unless the perimeter of the room was foamed and all the gaps filled. I dont think ive ever seem a wunda system
Or any other overlay system i would trust LVT on levelling compund. So many potential issues from the first day on installation to the last.

 

Could possibly be the wire pressing down into the board beneath and with the screed being so thin, it has just gone down with it. Is it just in the main traffic areas or has it also gone where it has barely been walked on?

 

Just out of interest, what does the back of the plank you lifted look like? There doesn't appear to be much adhesive left on the floor

 

What year was your house built. Was the concrete they went over older then 1980?

 

The screen depth Wunda recommend is a 5mm (the UFH pipes go into a formed tray and they calculated and supplied exactly that, 21 bags. My fitter bought additional bags separately from Mapei to fill the channels in the trays where we didn’t have any UFH pipes. He of course ensured that the depth was 5mm as it was put down. It does seem to be more in the higher traffic areas

 

The house was built in the early 90’s

 

5mm?
Really...thats a thin coat.
Sounds like the black stiff could have been a dpm they put down in that section you mentioned but if there wasn't any moisture readings from the start then it could be down to the whole floor needing a dpm before going forward with the rest.

From your other thread there didn't look like there was any adhesive transfer either, does look like the whole job wasn't spec'd correctly but hard to say without knowing the main issue why the screed has blown...

Could be the whole floor needed a dpm, screed wasn't thick enough, no primer used etc

 

Should be 10-12mm min depth, was the boards cleaned and primed first, also are the overlay boards bonded to the subfloor ?

 

unfortunately these retro fit under floor heating suppliers change their advise more than their pants. Its a big money maker and it causes alot of issues. Ive seen loads and non of them work properly.

 

Sure I read somewhere minimum was 10mm for the wunda and that's after the pipes are buried minimum 55mm but I'm guessing you had the different system.

Which actual product did you have?
Was it the boards?

 

It was the Rapid Response system. I’ve added a picture. I have added a picture

 

How could I actually find out what’s going on conclusively?

Also, is does anyone know if there is any hope through my home insurance?