Moving a tub and installing a shower

[MasterPlumbersKeymaster]

I am in the prelim stages of a major bathroom renovation. I am thinking about moving a tub 36″ inches in a straight line. Where the tub was, I will be installing a shower. Where the new tub location is, I will need to bring in water lines and hook up the drain. I was told that if the floor joists run in the same direction as the straight line the tub is moving in, there should be no problem hooking the new drain position up with the old drain position. However, if the joists run perpindicular, this will most likely pose a problem. Their solution was to open the ceiling of the floor below. Obviously, I would like to avoid this. Is there any other way? How about raising the floor where the new tub location is. If this is possible, how much do I need to raise the floor. Many thanks

[Retired plbg1Participant]

You will have to be judge of raising your floor, but let you know you need a 2″ drain and vent and trap, if you raise floor the trap will govern your hight.

[nicktheplumberParticipant]

As you note, the best way to reroute the drainpipes is to work from below. If you have an unfinished basement below your current bath, the job will be easy. It sounds like you have some sort of finished room below, since you mehtion opening up the ceiling. If that is the case, you will either have to open the ceiling or you can work from above by removing the floor in your bathroom.

If the joists runn parallel to the length of the tub, you will have plenty of room to lay out the new drain extension. If not you will have to notch or bore the joists to admit the new drain extension. The shower requires a 2″ drain, but you can get by with a 1 1/2″ drain for the tub. If you have to bore or notch up to 2″ holes in an 8-10″ joist, you should be OK, especially for a 3-4 foot run. For added strength you may want to sister the cut joists and add blocking on both sides of your cuts. The joists under a tub or shower should be sistered in any case to bear the extra weight.

You will need to pay attention to the slope of your drain extension (min. of 1/4″ per foot). With a 36″ extension you should be OK.

It is possible to build up the floor under a tub/shower if you have enough ceiling height in the bathroom, but this is not an ideal way to go. The extra height of the fixrures creates a clumsy step up. And when the entire bathroom floor is raised in this manner, it leads to a clumsy step up into the bathroom.

NtP

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