[mieno]

Hi
If I was to use insulation boards over the vermiculite concrete layer (to improve the insulation effect), do I need to glue or mortar the boards to the vermicrete? If so, what is the material to use?

Also, do you spread an underfloor paste of sand and fireclay over the boards if you are laying down a modular refractory concrete floor as opposed to a brick floor?

Thanks in advance.