Lay external slate tiles directly onto insulating board?

[rarem]

I need to lay a small (6sqm) patio. I wondered if can lay my slate tiles directly onto Marmox or Wedi insulating backer board?

I would like to do it this way because it's for a small roof terrace and I'd like to keep the weight down - if I can avoid using a mortar or cement bed I will save a lot of weight.

Any thoughts?

 

[tictic]

when you say its a "roof terrace"..what is the substrate made of?...

 

[rarem]

Hi tictic - the substrate will be 100mm of kingspan h350r - this is a completely waterproof insulation foam. I was going to lay the tiles on 50mm of concrete mix on top of the kingspan but the marmot would save me a lot of weight.

What do you think?

 

[mikelyonstiling]

Rarem
It doesn't sound as though the base is going to be that stable so I'd suggest using an exterior ply, Ditra matting (or similar) and a good adhesive like 'Rapidflex' from Nicobond with a high quality flexible grout.

The base must have NO movement whatsoever, other than minimal flexing or expansion/contraction.

Mike Lyons