With the walls of the old closets removed, the framing could begin to form the layout and physical boundaries of the new bathroom.  It also meant that the design could be modified (easily) so we had to be certain about our plans.

Photo: Screws used for framing
I have a small compressor that's great for finish and brad nailing, but not framing.  I decided that it'd be cheaper and easier for my small project to use screws for the framing instead of renting a larger compressor and framing nail gun.  I had picked up a nice Bosch impact driver that did the trick -- it's light and plenty strong enough to whip through the project I had.

The framing was straightforward, the only delay was laying down some new oak flooring to patch in where there was plywood on the floor (hidden by our washer and dryer).  In addition to the framing, we put in a new window so there would be some natural light into the bathroom.  We didn't want a full size window because it'd be in the shower area and the water would destroy it pretty quickly.  We decided upon a vinyl window and I'd use some waterproof material to frame it in the tiled bath.
Photo: Starting to frame bathroom wall
The window went in quickly, as did the rest of the wall.  I put in insulation, plastic/waterproof layer and then finished with some felt paper.  I had to use some odd spacing to make sure there was stud walls where I need them, but those were in addition to the 16" OC walls I had.  I wanted to make sure I had something to nail into at the end of the tub as well as decent blocking for my sink!
Photo: Electrical for fan and sconce lights
Photo: Insulation on wall
I had also decided to add some sound-blocking insulation since the kid's playroom would be just opposite one of the walls.  This would keep things quiet and personal in the bathroom even if it wasn't really critical or necessary.

The electrical was pretty straightforward.  I had put in a fan at the end of tub so I made sure it was UL approved for a wet location -- which it was, as long as it was on a GFCI circuit.  I also made sure the GFCI outlet was on a different circuit breaker than the lights in the bath per code.

With the walls in place and some insulation on them, I could really see the shape of the bath and get a feel of the space.  The plumber came in and put in the tub and roughed in the other plumbing.  Things were really moving along!