hey all, i'm about to begin my shower install. I have yet to research one areae, the sheklf. I have a shelf that is built from 2x4 timber that runsa along one side wall and then along the front wall of the shower. It sticks out about 6 inches, and is about 6 inches high. Since this is built entirely of 2x4's, how should I waterproof this area prior to tiling? Should i use extra 40 mil liner material and staple to the walls, than cover with lath and then deck mud?

Good idea ... but use "fat mud" which can be made from a bag of "mortar mix" (same stuff used for masonry work). It's easier to use on vertical areas because it clings to the lath beter.