You may need to cut through joists to accommodate the standard 4 by 3 closet bend beneath a toilet or the drain assembly under a standard tub. In that event, reinforce both ends of severed joists with doubled headers attached with double-joist hangers. This beefed-up framing provides a solid base for the toilet as well.
If joists are exposed, you can also add joists or blocking to optimize support.
A minimum 6-in. by 6-in. opening provides enough room to install a no-hub closet bend made of cast iron (41/2 in. outer diameter) or plastic (З1/? in. outer diameter). The center of the toilet drain should be 12 in. from a finish wall or 1232 in. from rough framing. If joists are exposed, add blocking between the joists to stiffen the floor and better support the toilet bowl, even if you don’t need to cut joists to position the bend.
A 12-in. by 12-in. opening in the subfloor will give you enough room to install the tub’s waste and overflow assembly. Ideally, there should be blocking or a header close to the tub’s drain, that you can pipe-strap it to. To support the fittings that attach to the shower arm and spout stub-outs, add cross-braces between the studs in the end wall. To support tub lips on three sides, attach ledgers to the studs, using galvanized screws or nails. Finally, if there’s access under the tub, add double joists beneath the tub foot.
a sleeve onto each end of the combo. Align the combo takeoff so it is the correct angle to receive the fixture drain you’re adding. Finally, tighten the stainless-steel clamps onto the couplings.
After modifying the framing, assemble branch drains and vents. Here we’ll assume that the new DWV fittings are plastic.
The toilet drain. After framing the tub drain opening, install the 4 by 3 closet bend, centered 12 in. from the finished wall behind the toilet. Install a piece of 2×4 blocking under the closet bend, and end-nailed through the joists on both ends. Use plastic plumber’s tape to secure the bend to the 2×4. What really anchors the closet bend, however, is the closet flange, which is cemented to the closet bend and screwed to the subfloor.
The flange screws to the subfloor yet will sit atop the finish floor when it’s installed. If the finish floor is not in yet, place scrap under the flange so it will be at the correct height. If, on the other hand, the flange is below the finish floor, you can build up the flange by stacking plastic flange extenders till the assembly is level with the floor. Caulk each extender with silicone as you stack it and use long closet bolts to resecure the toilet bowl. (Check with local codes first, because not all allow extenders.)
