With any substantial bathroom remodel, it's usually necessary to replace the bathtub or shower. Refinishing or re-lining the bathtub can extend its life a few more years, but for a total transformation that adds aesthetic value to the bathroom and resale value to the home, you'll want to replace the bathtub.
Bathtub replacement is a major project because it consists of several minor projects: demolition, plumbing, light carpentry, as well as fitting the tub into position and attaching it to the wall. Yet it's entirely manageable by most do-it-yourselfers,
Organizing the workflow into separate stages, giving yourself enough time, and calling for help when needed make this a rewarding, cost-saving, and skill-building do-it-yourself project.
Before You Begin
When shopping for your new bathtub, be aware that some tubs are marked as either left-side or right-side tubs, meaning the drain hole is either on the left side or on the right side.
It's important to purchase the correct tub because alcove bathtubs are not interchangeable. What appears to be a four-sided box actually has only one side—the front apron.
It is always less mess, less work, and far less cost to keep the bathtub plumbing in place. Moving the water supply and drainage from one side to the other will substantially add to the project cost. If you have any concerns about your ability to complete this project, which is rather advanced, hire a professional to do it for you to ensure it's done properly.
When to Replace a Bathtub
In a full bathroom remodel, replace the bathtub before installing the bathroom vanity and toilet. This permits easier removal of the old bathtub and helps with positioning the new bathtub.
Turn off electrical circuits and water to the bathtub perimeter before you begin. Be careful when removing the old bathtub: Cast-iron and steel tubs are very heavy. A common practice with removing cast-iron bathtubs is to first break them apart with a sledgehammer, then remove the tub pieces.
Equipment / Tools
- Drain wrench
- Cordless drill
- Caulk removal tool
- Allen wrench set
- Channel-lock wrench
- Oscillating multi-tool
- Tape measure
- Chalk snap line
- Shop vacuum
- Circular saw or electric miter saw
- Caulking gun
- Self-leveling underlayment
- Roofing nails
- 1-1/2-inch waste and overflow drain assembly
- Plumber's putty
- Bathroom-grade silicone caulk
Turn off Water
Shut off the water supply at the main water shut-off valve. Your bathroom may have a separate valve for the bathtub located in an access panel. If so, shut off the water here instead of at the main shut-off valve.
Remove Drain and Overflow
Remove the tub drain stopper. Remove the tub drain with a plug wrench. With the screwdriver, turn out the screw holding the overflow drain cover and remove.
The tub faucet may have a set screw underneath that turns out with an Allen wrench. If not, you should be able to unscrew the faucet by hand by turning it counterclockwise.
If you intend to remove the entire bathtub surround, you will need to remove the tub controls, as well.
Access Tub Drain
To detach the bathtub from its drain, you will need access to the area underneath the bathtub. Do this through a wall in an adjoining room or from a room underneath the bathtub.
Disconnect Tub Drain
Use a channel lock wrench to unscrew the tub drain fittings under the tub. Be gentle to avoid breaking the fittings. The entire section comprising the tub drain and the overflow drain should come off in one piece, leaving the rest of the drainage system that leads to the main waste line in place.
Remove or Cut Away Tub Surround
If you intend to replace the entire bathtub surround, remove it now. If not, remove only the bottom few inches of the surround that meet the top of the bathtub.
With the tape measure, measure upward 6 to 8 inches at several points along the bathtub surround. Then, use a straight edge or a chalk snap line to mark it continuous line. With an oscillating multi-tool or a manual drywall jab saw, cut away this lower section of cement board or drywall. Use the caulk stripping tool to first remove the caulk, then pull out the lower section.
If the surround is covered with tile, this section of tile will first need to be removed so that you can gain access to the cement board or drywall underneath.
Remove Tub-to-Stud Fasteners
Nails or clips will be holding the top flange of the bathtub to the wall studs. Use the pry bar or hammer to pull out the nails or clips.
Detach All Other Obstructions
Look around the front face and apron of the bathtub for any other fixed objects that might obstruct bathtub removal such as baseboards, vertical trim, shoe molding, or trim along the bottom of the bathtub. Strip out any caulk between the bathtub apron and flooring.
Pull out the old bathtub. In some cases, enough of the obstructions may have been removed so that you can pull the bathtub straight out.
If not, you may need to tip up one side of the bathtub to a vertical position, then remove it from the alcove that way.
Remove Bathtub Stringer
With the hammer or cordless drill, remove the fasteners holding the horizontal bathtub stringer from the wall studs.
Assess and Prepare Tub Area
Clean out the tub area with the shop vacuum. Assess the entire tub area for needed repairs. Wall studs and insulation around top areas often are moldy. Eliminate the mold and replace any poor structural elements, including studs, subfloor, and joists.
Level Tub Area
The floor under the bathtub must be level in all directions. Check the level with a bubble level. If you are rebuilding the joists and subfloor, you can create a level floor this way. If you are not rebuilding but the floor is out of level, pour a self-leveling underlayment on the floor of the bathtub area.
What Is Self-Leveling Underlayment?
Self-leveling underlayment, also known as leveling compound, is a viscous masonry product that settles, self-levels, and hardens to create a flat, level installation surface.
Mark Tub Flange on Studs
Slide the bathtub in place. With the pencil, mark along the top of the bathtub flange across all of the wall studs. Remove the tub.
Measure Bathtub Flange Height
On the bathtub, use the tape measure to measure the distance from the top of the tub flange to below the flange. It may help to lay a piece of scrap two-by-four under the flange to help visualize where the tub stringer eventually will be.
Install New Tub Stringer
Take the measurement from the previous step and transfer it to the wall studs. Begin at the marks on the studs made earlier and measure downward.
Use the circular saw or electric miter saw to cut a two-by-four to the length of the tub. Nail or screw the new tub two-by-four stringer on the wall at the lower marks.
Install Tub Drain
Place the bathtub on its side. Roll a bead of plumber's putty between your hands to form a ring to go around the tub drain flange.
Put the tub drain flange into place from the top (the basin). Screw the drain shoe into place from the bottom of the tub.
Tighten it with the drain plug wrench. With your finger, scrape off excess plumber's putty.
Attach Overflow Drain
Add the rubber gasket to the overflow drain. Hold the overflow drain to the back of the tub and screw it into place from inside the tub.
Connect Overflow to Drain
Connect the overflow pipe to the drain pipe.
Attach Tub to Studs
With an assistant, move the tub into place, being careful not to damage the drain pipes.
Attach Drain Assembly to Rough-in Drain
Underneath the tub, check that the drain assembly perfectly lines up with the plumbing rough-in. Attach the two pieces.
Secure Bathtub to Studs
Nail the bathtub flange securely against the wall studs. Check with the bathtub instructions, as some may require you to nail through the flange and into the studs, while others may require you to nail over the top of the flange with roofing nails or clips.
Fill in the removed portion of the wall surround or install an all-new tub surround. Reinstall all baseboards and trim. Caulk between the bottom of the wall surround and the top of the tub. Caulk between the tub apron and the bathroom flooring.
Tips for Replacing a Bathtub
For easier installation, look for matching bathtubs and wall surrounds. Since these tend to be brand- and model-specific, you won't be able to match one manufacturer's tub with another manufacturer's wall surround.
If the bathtub does not have easy access from a floor below, create a permanent access panel in the adjacent room. This helps if you ever need to check on or repair the bathtub plumbing in the future.
It's not necessary to build the 1-1/2-inch waste and overflow drain assembly from scratch with individual pieces. Complete kits are available that contain all parts to attach the tub to the rough-in plumbing.
When to Call a Professional
You may want to have a licensed plumber perform the bathtub rough-in work. The plumber can also attach the overflow and drain assembly to the tub. If the bathroom floor or walls are in poor condition and need replacement, hire a contractor or a carpenter for this job.