How to Set a Bathtub in a Bed of Concrete

Measure the length and width of the base of the bathtub with a tape measure. Mark the floor with the tub measurements using a piece of chalk.

Cover the floor area where you’re installing the bed of concrete with roofing felt, if the subfloor beneath the tub is made of wood. If the subfloor is concrete, then no felt or wire covering is necessary. Cut the felt to fit the floor area with a utility knife, and then staple it into place using a hammer tacker. Position the staples every 6 inches throughout the felt surface.

Cut a sheet of wire mesh to fit the same area as the felt using a pair of tin snips. Place the mesh over the felt and then staple it into place as well, spacing the staples every 6 inches.

Mix the two bags of mortar with water in a wheelbarrow. Turn the water into the mortar using a spade, adding a small amount of water at a time until you have a mix about the consistency of a thick batter.

Spread the mortar over the wire and felt, or over the bare concrete if installing the tub onto a concrete bed. Make sure you don’t get any of the mortar into the drain area for the tub. Build up a layer of mortar about 2 inches thick.

Cover the mortar with 6-mil plastic sheeting to keep the concrete from sticking to the tub, making it possible to remove the tube easily at a later date if desired. Cut the plastic sheeting with a utility knife to fit over the bed.

Place the bathtub in the center of the bed, and then push it down into place. Place a carpenter’s level across the rim of the tub and adjust the tub’s placement to make certain it lies level in the bed. The mortar bed will conform around the tub’s body, holding it snugly in position. Leave the mortar for 48 hours to allow it to cure firmly.

Make the pipe connections to the tub as needed, and screw the tub to the wall studs surrounding it using a drill containing a screw bit and wood screws to secure it in place.