Standing by for the Orange Kool-Aid.
This I got to hear.
Please John Bridge tell us how your little label on Kerdi will trump Tom's building department?
I can't wait.....
Tom what city are you in. I'm going to call and speak with the city inspector just as a double check for you. I do love my calling plan!
While we wait for John to chime in here is some resource information for you.
Letter of approval for Hardie Board from the city of Los Angeles - http://www.jameshardie.com/homeowner/pdf/larr24862.pdf
This list of requirements from The City of Concord - http://www.cityofconcord.org/pdf/per...om-remodel.doc
Moisture Resistant Gypsum Board (blue/purple board can be used for solid surface materials only)
Backing that is permitted to be used as a base for wall tiles and panels in showers are covered as follows:
All products must extend at least 70 above the drain inlet.
All products must comply with ASTM C 1178, C 1288 or C 1325.
All products must be installed in accordance with the manufacturers installation instructions.
So no drywall in this list for tile - shocking. The requirements C1178, C1288 and C1325 do not list regular drywall. These references are for denshield like products and cementious products only.
A. Fiberglass Mat Backer Board (DensShield, GlasRoc or other approved products)
Do not install a water-resistive moisture barrier behind Fiberglass Mat Backer Board.
INSPECTION: Required after completion of taping
I love this. California is so ahead of the nation. Mine and yours. Inspections for backer boards I love it. Note that California does not want a water - resistive moisture barrier behind the fiberglass mat backer board.
B. Cement and fiber-cement Backer Boards (Hardi-backer, Glas-crete, Durock)
A water-resistive moisture barrier is required behind cement board (such as 15# roofing felt or Grade D building paper).
INSPECTION: Required after mesh tape is applied.
Note that California does want a water - resistive moisture barrier behind cement board.
C. Original Mortar Backed Ceramic Tile (Lath and plaster)
A water-resistive permeable barrier with a performance of one layer of No. 15 asphalt felt, or Type 1 felt or other approved materials is to be installed behind lath.
A water-resistive permeable barrier with a performance of at least to two layers Grade D paper is required behind lath applied over wood base sheathing.
INSPECTION: Required prior to mortar application.
No drywall for tile - anywhere. And since you need an inspection before covering with mortar there is no way to sneak Kerdi in over drywall!