Custom Shower Pan with Membrane (Threshold Question)


Hi all,
I am currently building a custom shower, and have been following the directions from a DIY book, and getting useful information off the web. For the most part, the instructions from all sources are consistent: 1. Layer of mortar sloped to the drain 2. Felt paper over mortar to protect membrane 3. Membrane, with proper seal around drain assembly 4. Backerboard on walls, down over membrane, but 1 1/2 inches off the pan floor 5. 2 - 2 1/2 inches of mortar with pea gravel around weep holes to prevent cement from getting in the holes
What I haven't seen explained is what happens to the inside of the threshold to prepare it for tile? Should a narrow strip of backboard be screwed to the inside of the threshold (but kept 1 1/2 inches off the floor), and mortar over the top like the other interior walls? It seems like screwing the backerboard on the inside of the threshold would compromise the membrane? I've seen a few pictures of the steps involved, and it seems that everytime they get to the final bed of mortar, the threshold and inside of the threshold appear to be exposed membrane. Can you simply tile over the membrane???
Any help would be greatly appreciated!
Thanks and Best Regards, Todd
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At the thresholed wire lath in a single or double layer is bent to fit snugly over the lumber framing the threshold, NO FASTENERS PENETRATE THE MEMBRANE Mud is trowelled on and pushed through the lath and a slight inward slope is created. three-eight-hotel wrote:

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Thanks for the reply! That makes total sense!
Would it be adviseable to put the lathing in place before I mud the floor (with the thought that the floor mud would hold the lathing in place at the threshold), or does it not really matter?
Another question I had was with respect to the threshold sides (and top)... Is green-board sufficient, as a base for tile, or is backerboard typically used in those places as well?
Thanks again for any advice!
Best Regards, Todd
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I would use mud on the threshold inside and top. You want no nails through the membrane. I wrapped the lath over the top and down about 1" on the outside of the shower, so that it would hold itself in place over the membrane. I nailed backerboard below that to help guide the trowel for shaping the mud.
I did see a pro who glued some kind of backerboard (siliconized gypsum?) to glued down membrane over the threshold. I believe he clamped backerboard to the threshold to press the membrane into its glue to attach it, with weights on the top. He used special glue for this.
Bob
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Thanks Bob! This seemed like a logical thing to do, so I did exactly that last night, except I didn't wrap the lath over and down, on the outside. I mudded the floor, which seems to have held the lath in place, just fine. Tonight, I will mud the threshold, and get ready to move on to tile! ;-)
I'm sure I'll be back soon, with some tile questions!
Best Regards, Todd
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