Shower surround questions

[Rcassidy]

We just had to replace our showerpan due to a leak (which ended up in a complete bathroom remodeling due to subfloor issues.) I'm down to the studs and understand the process of installing tile backerboard, but I'm confused about the sizing. Do I get backboard at a width to match my drywall, butt it against the showerpan, and make up the difference in width with thinset? When I look at the studs, there's about 1/8"-1/4" gap between the pan and the studs. Is that a problem, or am I overthinking?

Also, we ripped out the fiberglass insulation because of mold. We found that there is just flashing and our siding on the other side of the studs. Should I replace the insulation with fiberglass sheets?

This is the current state: http://imgur.com/a/S5OAX

 

[Reach4]

I suggest that you search for references to XPS.

 

[Sponsor]

 

[Jadnashua]

If that's an outside wall (and even if it isn't and you want some help with sound attenuation), you need to put insulation in there. you could use unfaced fiberglass insulation. Then, install a moisture barrier, typically a heavy plastic sheet or roofing felt making sure that it drapes over the lip of the tiling flange into the shower pan. Then, you'd install the cbu on the walls...you can terminate it just shy of the tiling flange IF the tile you are planning to use will be more than 50% supported by the cbu on the wall. If your selected tile will be too small, then you'd need to shim the walls out so you can bring the cbu down on the inside of the tiling flange. That will make trimming the edges at the outside of the shower more difficult, since that wall will then be thicker, not just by the tile, but by the cbu edge sticking out.