tiling over two diffrent subtrates

[Freeze]

John, had a similar job 4 years ago up in Derwent Bay, 185m2 floor of which 110m2 were on to a new screed with UFH. When we arrived we were shocked at the size of some of the settlement cracks, and the levels, 35mm out in places, to cut along story short, we overboarded with. 12mm hardi backer, plugged and screwed, with a two part flexi, leveled with a 50mm fibre based screed, then ditra.
At the time Hardi had never heard of anyone doing this, and when I posted it on another forum it was met with a few oohs and ahhhs, that floor is perfect, not one crack, Jaipur grand opus.

 

[Freeze]

Just to clarify, when I said screed, we used an Slc that went up to 50mm in one hit, researched it and got the one with the highest newton strength we could find

 

[afright]

I will be doing a 100m2 balcony end of next month screeded floor to ply floor so I will be using ditra overall then Schluter movement joint profiles between the two substrates.

 

[beanz]

John, had a similar job 4 years ago up in Derwent Bay, 185m2 floor of which 110m2 were on to a new screed with UFH. When we arrived we were shocked at the size of some of the settlement cracks, and the levels, 35mm out in places, to cut along story short, we overboarded with. 12mm hardi backer, plugged and screwed, with a two part flexi, leveled with a 50mm fibre based screed, then ditra.
At the time Hardi had never heard of anyone doing this, and when I posted it on another forum it was met with a few oohs and ahhhs, that floor is perfect, not one crack, Jaipur grand opus.

How did you avoid the pipes?

 

[Freeze]

They were buried in the screed 65mm so just used a 40 mm fixing

 

[beanz]

Just curious, but what's the purpose of the Hardy in this situation!?!

 

[Freeze]

We originally refused to tile because of some of the settlement cracks, and the levels, this was a 4 million £ house, with a half million refurb, ripping up the screed and underfloor heating and doing it again was out of the question at this stage, after two days of discussions with the main contractor, architect, screed suppliers etc, we were asked how we could move forward and start tiling, we decided that the best way was to bridge the settlement cracks with 12mm hardi, we didn't think 6mm would be man enough, we then levelled the floor with a SCL which could go up to 50mm, then ditra matted, out method of thinking was we were decoupling from the screed in effect twice, like Johnny said, sometimes you can't put a garuntee on your work which we were not prepared to do, the screed suppliers and underfloor heating company covered all our material and labour costs, and the main contractor out in writing to every one concerned that he would take sole responsibility if their were any issues with the tiling

 

[Freeze]

John, sorry to high jack your thread mate

 

[beanz]

I think if you fix mechanically, you aren't decoupling, as the hardy will have to go with the screed. Maybe the hardy screwed either side of the cracks would add some structural integrity though... I must admit, I wonder if the fibre reinforced SCL and the Ditra would be enough to do the job, but wouldn't like to be the Guinee pig in this situation.

 

[beanz]

I hope John doesn't see this as hijacking... Just discussing the problem!?!