Help! SLC fail - Self levelling compound failed Pro 50

[Budha7]

Hi All

I have an issue which I would like to hear your thoughts on.

I have had a floor fail on me, and need to get to the bottom of what has happened.

The floor is timber, screwed to joists and checked for deflection.
Then overlaid with 10mm backer board, screwed to floor. No primer.
UFH loose wire system laid and covered with Norcros Pro 50 leveller.
Ardex AF200 adhesive for holding Ditra mat.
Norcros Rapid flex ontop for tiles.

The tiles are all moving, and on cutting a tile out, it is the SLC which has failed.
It has big cracks in it, which are curled at the ends. Raised around 5mm on the edges.
The only way I can describe it is if you can imagine a dried out lake bed?
The room never got above 15c when i was working there, the windows were closed and the customer was on holiday, so all heating was off and no hot water was being used (warm pipes).

I have photos and will try to upload, but i am unsure how at the moment, bear with me.
Can somebody please help!!

Thanks for the great forum!

 

[TJ Smiler]

So you had timber floor (what type? floorboards, chipboard etc?) then you over boarded with backerboard, then layed the UFH then applied SLC, then layed Ditra, then tiled. is that the order you done it in?

 

[TJ Smiler]

What type of tile?

 

[Budha7]

22mm t and g moisture chipboard flooring, laid opposite way to joists, offset, glued and screwed, with additional screws at 300mm centers.
Porcelain tiles.

 

[Budha7]

thanks for the quick replies, im trying to post pics now

 

[Budha7]

 

[TJ Smiler]

Did you put the UFH under the Ditra?

 

[Budha7]

Hi TJ
Yes ufh under ditra

 

[Rosco100]

Did you put the UFH under the Ditra?

dito

 

[Budha7]

So you had timber floor (what type? floorboards, chipboard etc?) then you over boarded with backerboard, then layed the UFH then applied SLC, then layed Ditra, then tiled. is that the order you done it in?

yes, correct.

 

[White Room]

What backer boards, hardie don't do 10mm....

 

[Ajax123]

That looks like it's been cooked. Underfloor heating too soon or too hot. What you are describing is classic thermal shock. I suspect some one is not telling you the truth about the sequence of heating post tiling...

 

[AliGage]

Any put the UFH on?

 

[Budha7]

floor was down nearly 3 weeks before it was turned on.
I have checked the customers stat (intelligent), as far as i can tell it hasnt been above 27c.

 

[TJ Smiler]

It could just be me not seeing your photo clearly but it looks like there is not a shread of adhesive underneath your ditra.

The SLC could have cracked if it was to dry. Others may not agree with me but i never put anything on chipboard, even the moisture board. How wide apart are the joists and were you able to screw down all the corners of all boards? or was it just screwed down every 300mm along the joists?

 

[Ajax123]

floor was down nearly 3 weeks before it was turned on.
I have checked the customers stat (intelligent), as far as i can tell it hasnt been above 27c.

it is either thermal or early drying shrinkage which you would have seen before you tiled. The dry lake bed though is absolute classic symptom of over heating too early in the process. Someone isn't saying something IMO.

 

[AliGage]

That looks like it's been cooked. Underfloor heating too soon or too hot. What you are describing is classic thermal shock. I suspect some one is not telling you the truth about the sequence of heating post tiling...

My thoughts exactly

 

[Budha7]

The adhesive for holding the ditra is Ardex AF200 - ditras specified glue.
The SLC was made using the manufacturers spec as to the amount of water.
400mm joists. all corners screwed and full length down sides and centers.
its all very strange.
thankyou for the replies!!

 

[demi34]

Underfloor heating should be on top of ditra and not under

 

[Spud]

get the norcross technical involved they will be able to tell you what went on i would have thought

 

[Ajax123]

Underfloor heating should be on top of ditra and not under

I don't think it really matters from a purely mechanical point of view.

 

[White Room]

Underfloor heating should be on top of ditra and not under

Not necessarily, Schluter state either....preference below ditra.

 

[Budha7]

whoa. if thats the case, how do I prove that?
On turn on the floor was 20c, I turned it on, as far as I am aware, i then programmed it to 24c for 3 days, then upped it to 27c. Which as far as i am aware is where it is stayed?

 

[Budha7]

 

[Spud]

whoa. if thats the case, how the F. do I prove that?
On turn on the floor was 20c, I turned it on, as far as I am aware, i then programmed it to 24c for 3 days, then upped it to 27c. Which as far as i am aware is where it is stayed?

was it turned on prior to the thermastatic control being fitted ? it happens a lot some sparks wire it to a plug end for testing i had one try it on my job last week

 

[Budha7]

Thankyou all very much for your replies, im trying to reply as quick as I can while putting my daughter to bed.

 

[AliGage]

Underfloor heating should be on top of ditra and not under

Why???

 

[Budha7]

I have actually been in contact norcros technical prior to being on here.
I am not happy with their response.

 

[Budha7]

I wired it up, so i know it is correct, but good point.

 

[andyb1]

What was teir response then.