large 60x30cm porcelain tiles on suspended plywood with backerboard?

[Mirjam]

Dear Tilers Forum,

On our ground floor - for various reasons, which I don't explain here, we want to put down:

- existing concrete
- vapour and radon barrier
- insulation boards and 70x25mm wood battens
- 18mm hardwood plywood
- 6mm hardiebacker

then the question: CAN WE USE LARGE PORCELAIN TILES (30X60X9mm) ????
or are smaller tiles preferable? (30x30x9mm) for example?
if so, why?
Thanks,
Alexander and Mirjam.

 

[Andy Allen]

why dont you just tile to he concrete ?

 

[Mirjam]

2 reasons:

- we want floor insulation, since it is the ground floor
- there is bitumen based aspestos glue on the concrete which we prefer not to scrape off, but rather cover it up as we have been told by aspestos experts. because of the bitumen we cannot glue anything onto it (otherwise we could use strong insulation boards instead of the ply construction.

why dont you just tile to he concrete ?