I will be roughing in a bathtub drain under a newly constructed, raised foundation. The joists and ghirders are already in place. I am not sure how to locate the tub and shower drains since I do not yet have the dimensions of these fixtures (in particular, the tub). Do I install the P-trap when roughing in, or is there another strategy for doing the rough-in in this case? I know where the vent line will be located, but only have a ball-park for the drain itself (especially for the tub). I looked at another construction site's rough-in plumbing, and think the drain line was just angled up to the general facinity and capped, w/o the P-trap installed; I believe it came off the sanitary tee, from which the drain line was connected.

Any tips/suggestions or references would be greatly appreciated. FYI, the code enforced where I am located is UPC 2000.