Check the dimensions of the tub to determine how big you need to make the tub frame. Tub frames are normally built to the length of the tub cubby -- the area framed into the home’s bathroom specifically for the tub -- while you determine the height and the depth -- front to back -- based on personal preference.
Allow at least 3 to 4 inches extra in height to provide a mortar/mud base for the tub to rest in and add depth, according to how much of a deck platform you want to include. Tile is usually installed on the platform with the tub installed on top of the tile, or the tile is added up to the edge of the tub after it is installed.
Cut down 2-by-4 horizontal material, according to your dimensions. Use the tape measure along with a pencil and carpenter square to mark the pieces then cut them down to size with a miter saw. You need four pieces cut to the length of the tub and four pieces cut to the depth of the tub.
Make the vertical cuts for the studs that support the horizontal pieces, according to the height of the tub. Remember that the bottom and top horizontal pieces add a total of 4 inches to the height, which means you should take that into consideration when cutting the pieces. You need enough vertical supports to place every 16 inches along the frame, just like wall studs.
Screw the bottom horizontal pieces into the subfloor, according to the dimensions of the tub frame. Use a drill and 3-inch wood screws. Once those are in place, you can mount the vertical support pieces. Angle in the screws to mount the pieces to the base support pieces and along the wall studs where the tub frame meets the walls of the home on the sides and back of the frame. Check the pieces for plumb with a level.
Place the top pieces of the tub frame on top of the vertical supports. You can drill straight down through the top of the support piece into the vertical sections to mount these pieces and angle the screws into the wall studs where necessary. Use the level and adjust the overall frame, as necessary, before sinking the final screws into the wall studs as you need to have the frame plumb and level.
Cut a piece of plywood, according to the dimensions of the tub deck. Apply wood glue on top of the tub framing. Screw the piece of plywood down in place with 1 1/2-inch wood screws. Use the template provided with the tub to mark the tub deck and cut out the hole for the tub with a jigsaw.