I have a post and beam house and want to install a new bathroom upstairs. The visible beams in my first floor are what support the second floor, hence no joist space. My question is related to the plumbing for the tub. I figure I need to build a platform for the tub to sit on. I want to know how tall should this platform be to accommodate the plumbing underneath, i.e. the trap and drain? And how much larger then the rim of the tub should this platform extend for safety of entering and exiting the tub?

Thanks for your help/suggestions.

Good question ! You are thinking like a pro...

From your description I am assuming you are planning on installing Self-Rimming tub (SRT). Yes, this type of tubs require platform.

Height of Platform: Most of the SRTs are plastic. So, measure from bottom of the tub lip to the bottom of the tub. Add 2". Build rough frame according to this dimension. When tile finished, you will be setting tub into bed of light weigh concrete. That extra space under the tub will be absorbed by concrete.

Thickness of front wall: You can use 2x4 framing (actually it measures 1 1/2" x 3 1/2" ). Once tub installed it will overlap the wall by about an inch. Therefore you will have about 2 1/2" of tiled parapet wall to cross to get into the tub. However, I have seen this front wall framed with 2x6 and even wider. But, yes, the wider the front wall is - the harder it will be to cross over it.

Drains: Do not worry about drains. They are 2" and always fit within existing joist space. You may want to make sure you don't end up with drain directly on top of joist. Position the tub so you by-pass it. You certainly don't want to notch joists supporting bath tub.

I appreciate your answer, but I do not feel it applies to my situation.

I have no joist space between my 1st and 2nd floor - house is a post and beam with exposed beams.

The plan is to install a clawfoot tub, so there is some room under the tub, but as the sink has an S trap I would venture to say the tub would have one too as the legs on the tub are not that tall and the pictures of the hardware for the tub don't show this trap, so I imagine it must typically be in the floor and since I don't want to look at a trap hanging in my living room downstairs I believe I need to build a platform.

Now I can picture you situation much clearer...

Claw Foot Tub has enough space between bottom of the tub and floor to accommodate Overflow Assembly. However, trap is needed and required. Trap has to go under floor. So you will have to build about 6" - 8" high pedestal to hide the trap. Tub would be then standing on top of the pedestal.

However, there is a possibility that if your new tub stands close to one wall, you could run Tub Overflow drain all the way to the wall and install trap inside the wall. It would require "creative plumbing" approach and eliminate the pedestal. See the enclosed drawing for better visual of this option...

Ok - so basically I'm looking at the height of a typically step and not taller, so I think height you suggest would be resonable and safe. So I just need to understand how much bigger then the edge of the tub would be safe to allow someone to not feel like they would step blindly out of the tub and catch the edge of the step and risk falling off the step.

I am not familiar with Code regarding size of steps in this situation. However, this is definitely custom situations so I would do the following: Make a makeshift wall out of 2"x4" stock imitating edge of the tub. It should be as high as the finished height of the tub. Have the shortest person in your household to step over it. See, and measure, how far he/she steps + add few inches for comfort.

I can do that . And thanks for your patient help and explainations. I think I can this framed in next weekend.

Sure... no problem... that's why we are here ! If you need any help in the process, come back ! Milo