Plumbing set up help.?

Hope this helps. I am in the process of rebuilding my bathroom. there is no crawlspace under the house for maintence. So I am putting in a stem wall all the way around the room to put the plumbing inside of. Not only will the plumbing be in the house where it is warmer but it will also give me a 4 inch shelf to put things on. The drains is the only thing that will be under the house when i finish.