Hello again a.h.r.,
I'd like to thank the usual suspects in this forum who have answered many of my questions lately, and answered them well.
Almost always, I find the need to mention that I'm in albuquerque, where the relative humidity is 20% after the evaporative cooling. The dryness is almost mind-boggling for this product of Chicago, and there are features in this town that not many others have. I bet you don't know the one I mean yet, so I'll try to write the story well.
Leaks disappear in this town. There's no clay anywhere. My lawyer buddy left his hose on for 2 days and had a simultaneous leak in the city water going out to him. It all ends up in the same place: the rio grande.
The drain underneath the slab on grade is now exposed: 2" PVC. Around it is the adobe dirt that is everywhere else. It is porous and dense. I don't think I need weep holes in my drain if this shower cries to the rio grande. Furthermore, no weep holes allowed me to buy my client's drain at lowe's, where she prefers that I buy things, as she has a charge account that gets a modest discount, and, much more importantly, allows me to make purchases without having to treat the receipt like the ark of the covenant.
Anyways, (the heat of the day seems to be taking its toll), so if the object of the shower is not to be a complete dam but more of a funneler, then what do I for water-proofing, with an eye to the fact that I'm spending somebody else's money here, and you could either imagine that person as a sister or the person who feeds me, and I like to have money leftover so there's grub for all of us. I would think that a shower might make at most 2 cm^3 of water that soaks into it, and the rest goes down the drain, unless you f*ed up the plumbing or tiling in a big way.
A liter of water disappears near this drain in a less than five minutes. I'm a little concerned that I might check how quickly sand and water disappear in this region, but that's a separate post.
I'm convinced that I can use building paper to achieve what I could do with the shower pan liner that I bought today. So many times in my construction career I have seen people but vapor barriers where there doesn't need to be one, and this has the odd effect of undermining the vapor barrier. Tja!
As I think about it the matter more, I don't think I need a vapor barrier at all on the bottom. Matter of fact, I think I should get out the hammer drill and make several relief holes around the perimeter that penetrate the slab. Not unlike the city of abq does to mitigate the exxon valdez that the air force dumped on us. Now that I think about it, since I'm north and east of the base, it might not be relevant to our location.
I learned last night that the rio grande is mostly underwater. It goes down a 1000 feet deep at the middle of the valley.
Am I thinking crazy?