Installing a tub isn’t an easy do-it-yourself project because it involves working with a large, heavy object in a small space. If you have any misgivings about doing it, hire a plumber who has the experience to install it and the license to hook up the fixtures.
Placing the ledger board
The first step in installing a tub is to set in place a ledger board that supports the edges of the tub that contact the walls of the tub enclosure.
Push the tub into the enclosure and mark the top of the flange on the wall studs with a pencil.
Measure and mark the location for the top of the ledger, usually about 1 inch below the first mark.
Use the manufacturer’s specifications or measure the distance from the top of the flange to the underside of the tub; it’s usually 1 inch.
Use coarse drywall screws to fasten the ledger board horizontally and level across the back wall of the alcove.
Fasten shorter ledger boards to the ends of the enclosure, level with the board you install on the back wall.
Doing so creates a continuous ledge on the tub enclosure wall for the tub to rest on.
Hooking up the plumbing
It’s easier to install the drain and overflow pipes on the tub before it’s permanently installed in the enclosure. Turn the tub over or rest it on its side and then follow these steps:
Follow the manufacturer’s directions and assemble the shoe fitting, which is placed under the tub and the waste pipe.
Assemble the overflow fitting with the overflow pipe.
Insert the ends of the overflow pipe and waste pipe in the T-fitting.
Put this assembly in place to check that shoe and overflow align with the openings in the tub.
Place a bead of plumber’s putty around the drain flange and wrap Teflon pipe tape around the threads on its body.
Place a rubber washer on the shoe and position the shoe under the tub in alignment with the drain flange.
Screw the drain flange into the shoe.
Tighten the drain flange.
Place the handles of a pair of pliers in the drain flange. Insert the blade of a large screwdriver between the handles of the pliers and use it as a lever to tighten the drain flange.
Place a rubber washer on the overflow drain and install the overflow cover with the screws provided.
You may want to leave the drain linkage and pop-up assembly out of the tub until you set it in place.
Securing the tub
Follow these steps to apply mortar to the subfloor of the tub:
Mix a batch of mortar according to the package directions.
With a notched trowel, spread a 2-inch layer of mortar on the subfloor where the tub will sit.
Lift the tub in place and position it so that it’s tight against the walls.
Hold a carpenter’s level on the tub and check that it’s level. If not, adjust it by placing wood shims under the tub.
After the tub is level, you secure it to the enclosure to keep it that way. Secure the flange to the studs by driving 1-inch galvanized roofing nails through the holes in the flange. If the tub is fiberglass, drill holes at each stud. If it’s a steel or cast-iron tub and it has no holes, or they don’t align with the studs, drive the nails above the top of the flange so that the head of each nail engages the flange. Hammer carefully so as not to damage the tub.