If you are installing a bathtub yourself, you will need to build a frame to support that tub. Maybe the tub you are buying is quite lightweight itself. When it is full of water, however, it will be very heavy, so it needs support underneath.
It also needs framing around the top so that the tile, water resistant paneling, or tub-surround you use will fit nicely up next to the tub itself. This article will include some tips and ideas for framing a bathtub.
Building a Framework to Support the Bathtub from Underneath
Of course, one of the most important aspects of building the framework to support a bathtub is that you measure carefully. Measure the area where the tub is going to fit and build the support. This is done by making a rectangle of two-by-fours and topping it with a piece of three-quarter inch plywood. The two-by-fours are to be standing on their narrow edge so that the resulting “box” is about 4 inches tall (not 2 inches tall.)
Add more two-by-fours within the rectangle (about every 12 inches) to further strengthen this “box” which will be used to hold up the tub. For best results, use screws to attach the plywood top to the base.
You will have to make a hole in the plywood to accomodate the drain pipe. Before setting the tub on the base, make sure the base is level. You can use shims to make it level if it is not. (The floor of the tub itself when properly installed will be slanted so the water is able to drain.) Then attach the frame to the wall and floor where you are about to place the tub. Attach it with long screws placed at an angle.
Around the Tub
Tubs come in different varieties, but the most common basic bathtub is designed to be attached to three walls. It has a flange around the three built-in sides. This edge needs to rest on two-by-fours which are attached horizontally to the studs of the wall.
Again, measurements must be as close as possible. Measure up from the floor and attach the studs around the sides. If you do this, you will have both a firm support beneath the tub as well as two-by-fours around the lip of the tub to support it there as well.
You will add wall board afterward so that it comes down over the flange to the top of the tub. The tub first needs to be nailed or screwed to the side supports.
Do be sure the wall board you use is of a variety that will not be damaged by water, and then make sure you seal it off well with caulk. Do not place the final bead of caulk in place, though, until you are real sure you have everything in place like you want it.
If your fix-it job merely consists of replacing an old bathtub with a new one, you may not have to do any new framing. If the old framework is rotted or damaged, you will probably want to replace it with new two-by-fours.
In addition, if the old floor supports are inadequate or non-existent, you may need to frame in the new tub much as you would if you were starting with new construction.