I am preparing to install a bath tub in a new basement bath. The groundwork is done, dirt's back in the hole and my next step is to re-pour the concrete. I know I need to leave a box around the tub drain and vent connections for hook-up later and have a few questions on the details.

1. How large and deep should this box be?
2. Should the box be centered on the approximate location of the tub drain?
3. Do the box walls need to be concrete, or is wood sufficient?
4. And, finally.. . When all is said and done, what do I do with this exposed box and dirt under my new tub? Is this left exposed, or do I fill in the trap box and top with a thin slab to seal the floor?

Thanks for your advice on these details.

- Peter

1. How large and deep should this box be?
2. Should the box be centered on the approximate location of the tub drain?
3. Do the box walls need to be concrete, or is wood sufficient?
4. And, finally.. . When all is said and done, what do I do with this exposed box and dirt under my new tub? Is this left exposed, or do I fill in the trap box and top with a thin slab to seal the floor?


1) this hole/box is called the tub "dap-out". And is usuallya 12 to 14" square hole as deep as the trap.
2) It should be centered on the traps raiser.
3)We do not build walls in a dap-out. The walls and deck are left bare, (more about that in #4.
4)You leave the hole open so the tubs drainage can be serviced. However if you're concerned about bugs and termites you can coat the walls and deck with roofing cement.
Good luck, Tom