wedi board on studs

[ladwey]

I was advised by a guy in the shop to get 6mm wedi board for tiling a shower cubicle. After attaching the wedi to studwork on one of the walls I called wedi just to check and they advised that it should be 10mm minimum on studwork. The studs are sizeable, closely spaced, and very well fixed. Am I ok to fix a second 6mm board on top to make up the necessary strength? I can use adhesive and screw through. The enclosure is already tanked, but if the second board is installed on top I'm assuming that will take care of it as there will be nowhere for the water to go, if I take care of the new screw holes. Thanks!

 

[foxhole]

What do you call close spacing?