Hi All,
I am looking to build a bathroom in our basement. The room will be positioned right next to the sewer line which exits just above the concrete floor. We have a drain pipe in place for a toilet and have to begin framing the floor and walls.
The toilet will have to be 9" off the concrete floor.

My question. The basement floor is not exactly level and I am wondering the best way to frame for the floor to get it level. I am thinking of going somewhere between 6 and 8" off the floor for the main flooring and then putting in a small pedestal to take up the rest of the space to get the 9" clearance where the toilet will sit by the back wall.

Should I frame the walls first then build up the floor or build the floor first then add the walls around it?
The bathroom will be as small as possible accomodating a corner shower, toilet and a sink with storage cabinet. Probably close to 6'x7'.

Any suggestions on approach?
The toilet will be attaching right next to the exiting sewer drain pipe so we do not have to get extra height, just clearance for the pipe and bend and I want to keep the main portion of the floor a little lower to give a little more head room in the shower which will not need much more than 6" clearance and still have adequate space for the trap and slight drop for draining.

It is not clear to me why you need more clearance for a closet bend than a shower trap.

You might want to also post this in "plumbing." "Speedball" is the local expert and extremely helpful on these issues.

The size of the drain pipe for the toilet makes the difference. It does not have to have the bend as a vapor trap but the pipe is very large and by the time it makes the full 90 degree turn up it is 9" from the floor whereas the shower trap only needs about 6" because the pipe is so much smaller.

I could post in plumbing but the question is really about how to setup the raised floor and attach the walls. The plumbing I should not have an issue with, I just gave details so it is clear what issues I have to address for the flooring.

Owl, I'd frame the walls first then the floor framing. This way you can attach the floor framing level to the sides of the walls studs. Then if there are any problems with the slab you can shim between the joists and the slab where needed. (use 2x8's and shim where needed. 7 1/4 (joist) 3/4" (plywood) = 8" close to what you need)
This way will also give you an easier way to run your plumbing because all the framing will be exposed. If you were to do the floor first, you'd have to plywwod the floor then build your walls thus concealing anything under the floor.

This help?

I have very little experience with construction but am reading up on things as I go so please excuse me if I use inaccurate terminology.

What I am mentally picturing from your description is this.
The existing ceiling joists are front to back.
I frame the walls with 2x4s with whatever the standard spacing is (I have the info, just do not remember offhand) attaching the top of the front and back walls to the ceiling joists. Not sure where the left/right walls will land yet and if they will be under a joist or not.
Then use 7 1/4" joists for the floor connected across the left/right wall studs, shimming each one to level it as I go then leveling the next with the previous so it is level side to side and front to back.

How would the floor joists connect to the wall studs? Would the end of the floor joist butt up to the side of the wall stud or drop in beside it? If butted up do I use something to assist holding them together similar to joist hangers?

I have a few books and lots of web articles for framing the walls but very little info for a raised floor.
What is sufficient spacing for the floor joists? Same as the walls or every other stud when using 3/4 plywood?

Recommendations on attaching the walls to the floor? I have seen some say to nail to the concrete and others to just glue down.

My preference would be to run the floor joists front to back rather than side to side since that is the slope of the floor and if there was ever a water problem it would drain more readily down the slope. I would just have to figure how the wall framing will work with the doorway there. I figure the bottom of the door should be level with raised floor, not with the basement floor so I would frame in that lower section anyway. That makes for an unusual height door though.

Oh, and when shimming the floor joists how do you ensure the shims stay in place? It's not like cabinets when you screw right through the wood and shims.

I have looked for examples of a basic room framing with a raised floor but have not found anything yet, just wall framing info. I could figure most of it out on my own if I could find some examples.

Thanks much for the info. I am hoping to start the project soon. The second phase of the project is recovering a goodly portion of the basement to use as my work area so I can expand out of the 8X12 space I have now. Little enough room there to store tools let alone use the table saw. :)

Joist spacing is typically 16" o.c. (on center) This means each stud will be center from the next 16". The easiest way to lay out walls, floors, roofs that require a 16" o.c. layout is hook the tape on one end of the wall plate and mark 15 3/4". Then at this mark, hammer a nail in the plate and hook your tape. Then when you pull the tape you mark evey 16" (16, 32, 48 etc). If you start from the right and pull left, as you mark the 16" locations put an "X" to the left of the line. This is the side of the line your stud will go on.

As for the floor joist, you can nail them to the side of the studs as you go. But, now you just increaes your floor height by 1 1/2" (plate thickness). If the final height is too high, you can knotch each joist end 1 1/2".

You can secure the wall plates to the concrete with glue, tapcon screws or use a remington 22 caliburn power driver.

If the joist goes acroos the door way either you'll have a step up or place the door on the floor if you have the headroom. You can always cut the door to height if need be.
The shims under floor stay put by a nail or screw and the weight of the floor.

Hope this helps. I have to type quick because sometimes my post won't post.

Anymore questions, post back.