On 2009-04-12, MiamiCuse wrote:

I have a bathroom with an exterior concrete block wall that I intend
to fur out 3" or so. The shower valve, the recessed medicine
cabinets etc...are all going to be taking up that space. I intended
to have a PT 2x4 as top and bottom plates and just use regular studs
every 16" or so.

However, along this 12' long bathroom, I have a PVC drain that goes
across about 9' of that 12' length. It is a lav drain but also
serves as a wet vent, hence it needs to be 2". The fittings that
fits outside of the 2" pipe makes it even wider.

Since you are furring out the wall, it seems like you should have
space for a proper vent line. This would also have the advantage that
both the vent and the drain would be smaller in diameter. You could
build the stud wall as you are running the DWV lines, to minimize the
number of couplings you use in the horizontal DWV runs.

With this pipe running across much of this wall about 18" or so
above the floor, there is no way I can put any studs on the bottom
plate without cutting 90% of that stud out.

The simplest method is this: Frame around the pipe like you are doing
a window opening. Put a long 4x6 header (solid or built up) over the
pipe, supported by jack studs, and a flat 2x4 "sill" under the pipe,
with cripple studs above and below. For extra strength, you could put
some concrete block anchors into the 4x6 header along its length,
counterboring them as needed. 9' is a long span, but for a non load
bearing wall 4x6 should be fine.

Cheers, Wayne