Kerdi Board. Kerdi. Kerdi DS
I wonder why the TTMAC specifies cement board in steam shower builds? Perhaps they feel that backer boards should not dissolve with heat and steam. In the TTMAC Specification Guiodelines there is only one backer board listed - It's Cement Board.
If you want Kerdi Board then make it. Use cement board and then cover it with Kerdi. You want a better board. Use cement board and cover it with Kerdi DS!
The facing on Kerdi Board is waterproof not vapour proof. Think about that - do you want a backer board that relies on cardboard to have that cardboard get we with vapour. Take a piece of cardboard - hold it over a boiling pot of water. What happens to the cardboard, I'll tell you - it weakens and then drops or bends down.
There is not Kerdi on Kerdi Board
Kerdi Board contains no Kerdi. It is a Kerdi looking fabric, Special reinforcing layer (looks like mdf), foam, Reinforcing layer and then Kerdi looking fabric. I believe the waterproofing comes from the glue that holds the fabric to the reinforcing layer. Kerdi Board is weakened once this MDF or reinforcing layer gets wet.
They use a paper like product to make Kerdi Board
This is Kerdi Fix (White Stuff)
Days and Days and Days later no leaks.
Tested the MDF layer with the orange fabric set with Kerdi Fix. This is waterproof, if you like using paper based products in your waterproofing systems...