Electric UFH UFH help! Wrong SLC used - Tile Advice

[Dipesh]

Hi all, I'm hoping you can advise me on a few things.

We have recently had underfloor heating installed. All was going well however whilst the builder was fitting the system, I noticed that he was using Everbuild 708 levelling compound to embed the wires. I could see anywhere on the packet that it is suitable for UFH.

The current situation is that the UFH is down and covered and 708 and looks well. However...

I rang Everbuild and they have confirmed to me that 708 is not suitable for underfloor heating and may potentially crack in the future!

This leads me to a few questions.

How likely is the 708 to crack when the UFH is in use?

Secondly, I have read about Durabase matting. Is it worthwhile me getting this put over what I currently have to ensure it doesn't crack?

The builder refuses now to do anything more and it is a fair size area (20+ sq m) so I'm looking for a cost effective solution as it will cost me a fair bit to get it taken up.

My plan was to have Karndean tiles fitted over this surface.

I hope you can advise me in the right path as I'm pretty anxious and feel really let down and my kitchen is in a right state!

Thank you.

 

[Qwerty]

If it's not flexible then it could very likely crack. Only time will tell.

Is there are expansion gap on the perimeter? Do you not have any comeback with the builder?

 

[Old Mod]

How can the builder refuse to correct his mistake?
If it's wrong and he's used unsuitable materials that he has chosen, then he's at fault, end of!

 

[Dipesh]

Thank you for your reply.

There may be a very small gap in some places but I don't think there has been any allowance made for expansion.

He seems to think it will be fine. It's only after I have called Everbuild to confirm they have told me this. I've not paid him for any labour, just materials (mats, adhesive, insulation mats)

I assume the insulation mats would be shot if it has to be lifted?

 

[J Sid]

as has been said, the builder (as happens to often) has used the wrong materials and has no option but to take everything up and start again at he's cost.

 

[Spacey]

He's used the cheapest stuff he could get his hands on there.

It's only suitable up to 6mm in thickness
Encapsulated UFH must have a 8-14mm coat to except karndean and the floor temp must not exceed 27°c max.

Builders are nobs in my experience and should keep away from floors full stop they only cocktail things up and cost people time and money.

Has your UFH Been commissioned?

I'd be tempted to turn it up full belt to give the screed a thermic shock.
Guessing he won't have used and primer either or not properly anyway. There's a good change it blow off the floor with out damaging the UFH.
Then ring him and tell it's all his fault
Don't mention what you've done though

 

[One Day]

No need to take it up. Get an uncoupling membrane such as BAL Rapidmat and fix that to the dodgy leveller, then cap that with 5 or 6mm of proper leveller.
Remove the cost of that from what you owe the builder and give him an invoice.

 

[Spacey]

I'd see if it'll blow first before you go any further Theres a good chance it wont be bonded. Also it's Karndean going down so would be laid in a wet set high temperature adhesive. When karndean gets hot it tries to expand If the screed isn't bonded well enough it will take it with it when it expands

 

[Dipesh]

Thank you gents. I will look at the Bal rapidmat.

The currrnt floor is at 5mm, when they fit the Karndean fitters will going over with a further level at 3mm to give it 8mm.

I saw him prime the floor, that bit looked proper and it was very sticky.

Would an uncoupling mat be ok with a 3mm levelling compound on top? I'm thinking floor height could be getting quite high with anymore!

 

[One Day]

Good point Spacey makes - if it is badly bonded it will ruin anything ontop. Best get it heated up and cooled down before deciding how to proceed.
As for minimum depth on top of Rapidmat, I'd suggest a call to BAL technical, they're always helpful: 0845 600 1 222

 

[Spacey]

Seriously don't go any further until you know what happening with this everbuild gear. It will only cost you more money in the long run.

What colour was the primer ?
Green or blue ?
Or was it white ish ?

 

[Dipesh]

Thanks guys. The primer was from the underfloor heating store that came with the kit. It was white and very running.

Do you suggest a procedure for getting it up to temp? How hot and for how long would you say run the heating for?

 

[Spacey]

OK I know what it is.

It the UFH visible or even still sticking up through the screed ?

 

[LM]

Everbuild is a cheap diy make, I completely agree with @Spacey with this. This will fail and anything you do above it will be relying on a sound substrate which this is not. The builder has cut the wrong corner here I'm afraid.

 

[LM]

If the leveller isn't flexible it won't survive.