Dents in screed appearing under LVT

Pretty sure that has to be 10mm screeded over

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I'd say not a chance, insurance won't cough up for the installer(s) negligence.
I've seen alot of these type systems installed without an issue, I've screeded over that type myself handful of times (I usually do electric mats) and I primed them twice, left to properly dry and have it 2 coats of screed, added up to around 12mm minimum but like merit says, this was a different manufacturer and they specifically told me minimum 10mm and had to use their spec screed (instarmac)

I've never heard of any manufacturer that says 5mm is OK over UFH.

If you take a chunk of the blown screed up and see underneath which assuming it's the foil boards then you'll see whether they primed or not but even so, 5mm is not enough.

 

I'm referring to screed depth when fitting LVT, ceramic is obviously different as you'd be able to tile straight onto the mats.


Sounds like there's been the wrong information given to your fitter but there's still a question whether they primed the boards or not.
For mapei renovation it still should have had a primer and of it has then at 5mm it's going to be a very weak bed.

Then you have the question as it left long enough before fitting on top...

 

Ive screeded over similar ufh maybe different brand and they also recommended instamac at minimum of 10mm as the foil boards do leave dents if too much weight is put on them ie chair legs tables etc. 5mm def wouldnt be sufficient on top to take weight

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5mm screed over polystyrene and water piped ufh. Its a no from me

 

Thanks everyone, you came to the same conclusion as we have but that is what they suggested, what they calculated in bags of Mapei on my invoice and what was used. What a total nightmare

 

A very expensive nightmare too if it all has to come up. Id def take a bit of screed up to measure the depth tho.

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That's ridiculous that is.
Didn't the Mapei rep query this when you told them 5mm?

 

Or what it them who advised wunda 'I wonder'
Surely not

 

Wait for then to tell you you've been running it over the 27deg

 

Floor tiles? They assuming ceramic

 

Says on tbe wunda site a thin layer of screed but no specific measurement

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This is what I've found as well

 

They word it to put the responsibility on the screed company 100 percent but strange for mapei to say 5mm

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Massive balls up.
Mapei would have told the customer the screed wasn't thick enough if it wasn't them that advised Wunda.

@Lisa Morgan they did know you was having Lvt fitted yes??

 

10mm above the height of the pipes, same for ceramics would need a ditra matting too, fitter should have known better whoever specified it is at fault though.


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Hi Lisa,

I’m about to cast a screed over wundatherm boards and I was very curious to know about the Mapei instructions regarding m2 per bag @ mm thick etc. I made up a sample board with the wundatherm boards and put in some sample pieces of 16mm ufh pipe again from wunda, so no grooves were left empty with unperforated foil over. Basically a solid piece of sample floor 0.4m x 0.4m. I then worked out the ratios as per the Mapei instructions exactly to the g of screed and the ml of water using scales. I cast what the ratio said would give me 10mm, once dried it ended up at 6mm.
The reason I did this was I’m about to cast 100m2 over a floor and want to get good coverage, but everyone had mentioned the screed doesn’t go as far as the Instructions. Guess that is true.
I only thought I’d mention because I did my sample accurately and thought it might be of use to you. Once Installed and the pipes pushed into the groove as far as they would go, some of the curves on the pipes also stood proud by 2/3mm. This is a problem I’m going to have to account for.

I can only assume that this may be your issue and the thickness of screed was the issue as a lot of people on here have advised. As a result I’m now going to add another 20 bags of screed to my job and cast at “15mm” in the hope of achieving a uniform 10mm.

Hope this helps you and possibly anyone else using these boards in the future.

Tom


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If the pipe Sat proud then the installer would have seen them unless he just thought sod it and besides that, they told her 6mm!!!

 

...but I do get what you mean but from an installers point of view it should be common knowledge

 

To be honest it looked flush until I ran a spirit level over it, but 2 or 3 mm is a lot when the screed is already thin.


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