Thin Large format porcelain - Tile Advice

[StevDev]

Looking to lay large format (900x900mm) thin (5.5mm) porcelain floor tiles onto a sand and cement screed (SR1). The tiles have a fibreglass backing. The screed is fully dry and has wet ufh.

Would you recommend a crack isolation membrane e.g., Ditra or similar, or lay the tiles directly onto the screed?

Proposing to back butter the tiles with 4mm notched trowel and apply adhesive to the screed with a 12mm U comb. Any comments? Thanks.

 

[Joy2019]

Would always recommend that any underfloor heating is tested and commissioned prior to tile installation, prime as required, Decoupling matting with S2 adhesive or recommended similar for best results.
Would use 3mm trowel to backbutter and 6mm on floor with slim tech tiles of 5.5mm thickness.

 

[StevDev]

Would always recommend that any underfloor heating is tested and commissioned prior to tile installation, prime as required, Decoupling matting with S2 adhesive or recommended similar for best results.
Would use 3mm trowel to backbutter and 6mm on floor with slim tech tiles of 5.5mm thickness.

Thanks for the advice. So I guess I'm looking at around 13.5mm in total height with tile, adhesive and Ditra?