How to Frame a Whirlpool Bathtub Base

Consult the manufacturer’s instructions for the recommended height of the framing. Mark this height with a carpenter’s pencil on your wall studs, which can adjoin one, two or three sides of the whirlpool. Double-check that your marks are horizontal with a spirit level.

Cut 2-by-4s to fit on your wall studs to act as ledger -- boards that essentially create a ledge of support for the whirlpool bathtub’s lip. Install the cut 2-by-4s with the long side vertical just under and snug to your height marks, by screwing two 1 1/2-inch wood screws through the ledger and into the wall studs.

Mark the subfloor at the manufacturer’s recommended distance for the width and depth of the unit; you won’t need to measure the width if the alcove already surrounds three sides of the whirlpool. Measure this distance from the wall if the alcove is finished or from the sole plate -- the 2-by-4 framing already on the floor -- if the wall is unfinished. Cut a 2-by-4 and screw it into the subfloor with its inside edge touching the mark. Cut additional 2-by-4s as needed if the whirlpool is not surrounded on three sides by an alcove.

Cut identical 2-by-4s to those now installed on floor, which are called sole plates in framing terminology. These newly cut boards will serve as top plates. Stack these nearby temporarily.

Subtract from the manufacturer’s instructions for the recommended framing height the depth of your cement backer board, the depth of your tiles, the thickness recommended for your tile and backer board mastic, and finally 3 inches for the depth of your top and sole plates. Cut short studs to this measurement, one for either end of the frame and additional ones every 16 inches on center.

Mark the locations of the short studs on the sole plate. Screw them into place by angling 2 1/2-inch wood screws through the bottom of the short stud into the sole plate and subfloor. This technique is called toe-screwing. Lay the top plate across the tops of the short studs and screw into place with two 1 1/2-inch wood screws through the top plate and into the short studs.