It all depends on the technique that both you and the contractor settle on.

The two most common are..

Poly sheeting or tarpaper are attached to the studs with a cement-type board fastened over it.

Or, the wallboard or cement board is fastened with NO backing, but the face is covered with a "SAM." or Surface Applied Membrane. Examples of this would be Hydroban liquid from Laticrete or Kerdi waterproofing membrane from Schluter.

I prefer the SAM, simply because moisture never penetrates the wallboard as it will in the first example, and the shower dries out much quicker. Both products mentioned have their own proprietary drain that should be used.

Videos for both systems can be seen on YouTube under Kerdi or Hydroban Showers.

Here's a great thread on the Surface Applied Membrane technique.

My contractor is going to do the poly sheeting behind the cement board, because that's the most I feel like insisting on (he doesn't think he needs it because we're using a shower pan). But I have a question: do you put the poly sheeting behind the shower valves/water supply lines, etc., or in front? If in front, how do you seal off the holes you need to make for shower fittings?

Here is a link that might be useful: Kerdi Instructions

but the face is covered with a "SAM." or Surface Applied Membrane.

What a difference a few years makes. :-) In another lifetime, my ship had launchers that could send 4 of those off at a time. (surface to air missiles) :-)

Surface-to-air missles? Sure, you might have shot them at the other side. But the "other side" used to shoot them at me!

Most definitely, in "our world" of SAMs, it's better to give than to receive...

My ship:
U.S.S. Harry E. Yarnell C-17

Launchers fore and aft with missiles on the rails are the SAM launchers.

Back to our regularly scheduled tech talk. :-)

THANK YOU for you service!!!!

Thanks for the blast from the past, you guys! I, too, did a double take when I saw SAM, though my relationship was not nearly as close as Bill's.

You want close?

This is just the training birds (the caption is a reference to the aircraft carrier on the left of the ship-- the U.S.S. JFK-- our main duty was as carrier escort):

This is the real thing at a firing range in southern waters:

Well, in Joyful-Life's opening post, she did write:

"We want to be armed..."

Though maybe not armed with SAMs?

Here's my old ride, the good ole' A-10:

Okay, Bill and I have air and sea covered. Any land warriors out there? lol

(Sorry Joyful-Life, but every once in a while we shed our cyber-identities and come out to reminisce...)

Reminiscing is certainly allowed! The pride of serving your country is evident. I think you guys are awesome (and I'm from Canada).

Mavericks are pretty sweet, too! :-) (BTW-- those particular DSAMS are Terriers)

Those A-10s have always impressed me bigtime. Not as fast or sleek as most of the other warbirds, but man, what a sh*tstorm those things can create!! One of my two favorite aircraft (the other is the F-14-- even WELL before top gun). First time I ever went out to sea, we were doing practice exercises off Va. Capes ("playing" war games). We were out there with several other cruisers and destroyers, as well as the carrier U.S.S. America, and she was sending planes in on us on mock attack runs to test our radarmen and lookouts (as a lookout, it was wild-- all you'd see is something right on the horizon that resembled a mustache, as they kick in the afterburners, 13 miles away. Five seconds later, they're already past you). Well, first morning out to sea, I was clueless as to what was going on. I was a slaphappy nonrate (deckape), polishing brass on the stbd side of the ship when all of the sudden, I look up, and here's this F-14, supersonic, about 50 feet off the surface of the water, and maybe 100 feet off the side of the ship-- so close we could see the pilot waving as he was going by-- as quiet as a whisper. When he reached the nose of the ship he yanked back on the controls, and went ballistic (straight up) in a spiral. About that time, the sonic boom caught up with us. Think of what it would be like to be standing in your yard, and oddly enough a bolt of lightning harmlessly stikes right next to you. Imagine the thunderclap you'd experience. Now imagine stretching that out for about 5 seconds. That's about what it was like, and not knowing WHAT the hell was happening, I hit the deck, face first. Of course I never lived that down. :-) TO THIS DAY, on my ship's facebook page, I STILL hear about that. :-)

Just to show I wasn't exaggerating. :-)

Here is a link that might be useful: Supersonic flyby