Tiles sound hollow under underfloor heating

[One Day]

200m2 with no expansion/movement joints! Even if everything else was done correctly this is wrong and could be the cause of adhesive bond failing and the tiles becoming loose.

Pretty sure that Ajax would say you don't need expansion joints actually. Anhydrite screed expands far less than usual. I'd still insist on ditra at that size though.
(yes, I know it's contrary to bs5385)

 

[J Sid]

but still need movement joints ? As the tiles would expand at a different rate to the screed but the Ditra may accommodate this movement

 

[Spacey]

Anhydrate isn't really a screed it's more related to plaster.
Its a bi product they needed to find a use for Builder's love as it's cheap pre mixed a great thermal conductor goes down smooth but most importantly for Builder's it dries quickly Randomly but quickly

 

[Old Mod]

yes, I know it's contrary

Not having that Mark, would never describe you as contrary!

 

[Spacey]

How do we deal with Anhydrate, Hemihrdyate subfloors?

 

[Kyle Knowles]

I don't I'd be skint

To be honest so would I I have a filthy mouth I'm trying to stop tho coz Mt 4 year old keeps copying me lol

 

[Simons70]

How do we deal with Anhydrate, Hemihrdyate subfloors?

Apply 2 coat of Kerakoll Primer A Eco Water-based surface primer that neutralizes the expansive chemical reaction of gypsum or anhydrite based plasters and screeds on contact with cement-based adhesives

 

[WetSaw]

Apply 2 coat of Kerakoll Primer A Eco Water-based surface primer that neutralizes the expansive chemical reaction of gypsum or anhydrite based plasters and screeds on contact with cement-based adhesives

...after removing the laitence of course!

 

[One Day]

The most bullet-proof method I know is
1 Remove laitence
2 Vac thoroughly
3 One coat chosen primer diluted (to reduce absorbtion)
4 Fix ditra with tm anhyfix adhesive
5 Fix tiles using whatever you like to use.
6 Good job, well done, sleep easy.

 

[Kyle Knowles]

The most bullet-proof method I know is
1 Remove laitence
2 Vac thoroughly
3 One coat chosen primer diluted (to reduce absorbtion)
4 Fix ditra with tm anhyfix adhesive
5 Fix tiles using whatever you like to use.
6 Good job, well done, sleep easy.

I wonder if this guy is ever gonna come back online I was actually looking forward to goin to represent the tilersforums and let him know what's what