All walls of whirlpool surrounds can be prepped using sheetrock.  However,
any ledges or steps must be prepped with cementboard or backerboard as
follows:
1.  Clean the floor of all debris.
2.  Mix latex modified thinset and spread on plywood with 1/4'' to 3/8'' trowel.
 
3.  Cut and place backerboard on thinset.
4.  Use 1 1/4'' to 1 1/2'' roofing nails every 8'' to secure board.
5.  Tape all seams using 2'' fiberglass mesh tape.
6.  Determine layout and patterns.
7.  Tile can then be installed using a 1/4'' square notched trowel or larger.  
It is recommended that you use a latex-modified thinset.
8.  Grout after 24 hours.  
9.  Seal grout after 72 hours.
Whirlpool Surrounds
TM
touchdowntile.com
touchdowntile.com
Whirlpools
2011.  Touchdown Tile is a Minnesota tile company.  All rights reserved.  All pictures of installed tile are Touchdown Tile installations.