Replacing shower floor - questions

Hi all:

I just discovered that my existing tiled shower has been leaking for some time, and has rotted part of the subfloor. The existing shower is in a corner of the bathroom, with tile along two walls, an adjacent tiled tub surround and a tile curb and floor. There is a custom glass & chrome surround on the two outer sides that fits over the tub surround and curb.

Once I repair the damaged subfloor, I plan to install a single-piece fiberglass (or other synthetic material) pan so this doesn't happen again. I have removed the lower 8" of tile on all three sides of the shower (2 walls and tub surround), and am completely removing the existing curb structure (which is partially rotten). I plan to cut the existing tile backer just below the lowest remaining tile, install the new pan, build a new curb, install new tile backer overlapping the flange of the pan, and re-tile down to the pan. I need to put back the curb or the existing glass surround won't fit. I have no desire (and no budget) to have a new surround made. Some questions are...

1: I can't find a shower pan without a threshold on at least one side. Does anyone make a one-piece 36x36 shower pan with flanges on all 4 sides (no threshold)?

2: If not, how do I waterproof the joint between the new tiled curb and the pan threshold since there's no flange? I am concerned that this might become my new leak point.

3: As I said, I will have to remove the lower part of the tile backer from the walls to get the new pan in place. How far up should this seam in the tile backer be from the pan? I'm thinking 8-12 inches.

Thanks in advance,

John.

Thanks for all the help.

Update:

As info, I do not believe anyone makes a pan with no threshold. I searched the internet for days, and consulted with every plumbing supply house within 25 miles of here. No one had ever heard of such a thing. The closest I got was a custom made cultured-marble pan, which was $400 and 3 weeks, plus 2 more people to install because of the weight. Also, the marble pan had no flanges, so I was concerned that it would leak if the bottom tile joint ever failed.

After completing the demolition, I found that a 42x36 fiberglass shower pan fits perfectly. Rather than trying to build up the threshold with tile, I plan to build up the subfloor beneath the pan so that its threshold is at the height of the original curb. The old glass surround should go back in just fine. No chance for leaks with this solution, as there will be no horizontal fiberglass-to-tile joint any longer. The new tile backer will extend about 20 inches above the pan.

My only complaint is that home centers don't stock 42x36 pans. Since it special ordered, it costs more than twice as much as the 36x36 pan that's in stock ($196 vs. $91). And, it take two weeks to get it.

As an aside, while investigating the adjacent wall cavities for rot, I found a beer can someone had left there. Perhaps this is why my old shower leaked. Seriously, from what I have learned recently while considering putting the tile shower back, I don't see why anyone would want one. You have to do all 50 steps of the installation exactly right. Get any one of them wrong, just a little bit, and the thing will leak. No thanks.

Regards, John.