Polystyrene boards

[Oddy1968]

I am about to prepare a floor with 10mm polystyrene boards, an electric heat mat and then tiles, do I go over the joints in the boards with wide masking tape or do you tape the mats to the floor from underneath?

Thanks Mark

 

[Monsoon]

Doing a similar job myself.

Taping the joints with a duct tape from the top