2 Effective Ways to Level an Alcove Tub

Co-authored by Eric Shipe

Last Updated: July 10, 2022 References

A new alcove tub is a great addition to any bathroom and something you can install yourself with a little DIY know-how and a helping pair of hands. Of course, you’ll want your new tub to drain properly, so make sure you get it completely level in the alcove before securing it in place! The manufacturer should give you an idea in the owner’s manual of the best way to get that particular tub model level.

Method 1

Method 1 of 2:

Setting a Tub in Mortar

1
Drill holes in the tub lip that correspond to stud locations in the alcove. Measure the distance between the studs in the alcove to confirm their spacing, which should be 16 inches (41 cm) apart. Use a stud finder if the alcove is finished and you can't see the studs. Measure and mark the spacing along the tub’s raised lip. Use a power drill to carefully drill a hole at each stud location.^{[1]
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- Note that the alcove framing and plumbing, including the drain opening, must be finished before you fit and level the tub.
- Use the appropriate drill bit for whatever material the tub is made out of. For example, if it’s a fiberglass tub, use a bit meant for fiberglass. It’s as simple as that!
- Make the holes the same diameter as the screws you’re using to mount the tub on the studs. For instance, if you use #6 gauge screws, the diameter would be 3.5 mm.
2
Mix a 55 lb (25 kg) bag of thinset mortar to a firm consistency. Read the packaging for the recommended amount of water and pour the water into a bucket. Add the mortar powder and stir it with a trowel for a few minutes until it is thick and pliable, but not runny.^{[2]
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- Thinset mortar is also known as tile mortar, so keep that in mind when you’re getting your supplies for this project.
- A 55 lb (25 kg) bag of mortar is enough for most standard-sized tubs, but you may need more if you’re installing a larger tub.
- If the mortar is too runny, you risk it spreading out too much and getting in the plumbing, which could clog it up and cause a lot of expensive problems!
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3
Pour the mortar onto the subfloor away from the drain opening. Slowly pour out the mortar towards the middle or back of the subfloor. Make sure it’s at least 3 inches (7.6 cm) away from the drain opening, so it doesn’t accidentally go down the pipes.^{[3]
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- If any of the mortar gets too close to the drain opening, scoop it away with a trowel and move it to another part of the subfloor.
4
Spread the mortar out into an even 2 in (5.1 cm) thick layer. Use a trowel to spread the mortar out using side-to-side strokes. Cover the whole subfloor in an even layer, keeping the mortar at least 3 in (7.6 cm) away from the drain opening on all sides.^{[4]
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- The mortar spreads out a bit when you set the tub in it and level it, so that’s why it’s important to leave plenty of space around the drain opening.
5
Push the tub firmly down into the mortar. Get a helper to assist you and lift the tub up together. Remember to bend at your knees and lift with your legs, so you don’t hurt your back! Carefully move the tub into the alcove, line up the drain holes, and set it down onto the mortar. Push it down until it’s securely in place.^{[5]
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- Thinset mortar takes 24 hours to cure, so don’t rush through the next steps of leveling the tub. You have plenty of time to work!
6
Check the levelness on all sides of the tub and adjust its position as needed. Lay a carpenter’s level along both short sides and both long sides of the tub. Check the levelness horizontally across the middle of the tub too, just to be safe. Adjust the tub by lifting it up slightly and pressing it down further into the mortar or wiggling it back and forth. Keep checking the levelness and making adjustments until the tub is perfectly level.^{[6]
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- Some tubs have adjustable feet that you can shorten or lengthen to raise or lower it in the front corners. You just screw them in or out by hand to adjust them.
- If you need to make any large adjustments, put wood shims under the edges of the tub to lift it higher out of the mortar in certain areas. Leave the shims there permanently—don’t worry, they’ll be hidden under the tub and won't affect its sturdiness in the mortar in any way.
7
Screw the tub to the studs with 2 in (5.1 cm) galvanized screws. Use a power drill to drive a screw through the first hole in the back corner of the tub lip, which you pre-drilled earlier. Check the levelness again, make any adjustments as needed, and do the same for the hole in the opposite corner to help keep the tub level. Continue to drive screws through each of the pre-drilled holes into each one of the studs.^{[7]
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- If there are gaps between the studs and the lip anywhere, place wood shims in the gaps and drive the screws through the shims into the studs to avoid damaging the tub’s lip.
8
Wipe away excess mortar and let the tub set in the mortar for 24 hours. Use a rag to wipe away any mortar that may have seeped out from underneath the front edge of the tub. Resist the temptation to try out your new tub and leave it alone for at least 24 hours to give the mortar time to cure, so the tub sets in place levelly.^{[8]
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- Some mortar can take longer than 24 hours to cure. Refer to the manufacturer’s instructions for the mortar you used to be sure.
- After the mortar cures, you can proceed to install the tub drain, caulk around the edges of the tub, and perform any other work that needs to be done in the alcove.

Method 2

Method 2 of 2:

Using Ledger Boards

1
Measure and add the height of the tub and the height of the finished floor. Use a tape measure to measure from the bottom edge of the tub to the underside of the lip at the top. Measure the thickness of the flooring in the bathroom. Add the two numbers together to get the height for the tub.^{[9]
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- The reason you measure both of these and add them to get the height of the tub is because you want the tub to be level at the height of the flooring in the bathroom. If you just measured the height of the tub, it would sit on the subflooring a bit below the finished floor.
- If the floor in the bathroom is already finished, you can skip the math. Just measure the height of the tub right now and measure up from the level of the finished floor in the next step.
2
Mark the height of the tub at one corner of the alcove walls. Measure the distance you got in the last step up from the subfloor, using your handy dandy tape measure again. Make a mark on the wall or on a stud with a pencil or a marker.^{[10]
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- If the bathroom flooring is already installed in the bathroom, you can instead measure only the height of the tub up from the top of the flooring near the corner of the alcove to make your mark.
3
Trace a level line around the alcove at the tub height with a carpenter’s level. Hold a carpenter’s level horizontally with the bottom edge lined up levelly on the first mark you made. Trace along the bottom edge on the alcove’s wall or studs. Move the level along the wall, lining the corner up with the previous line and adjusting it so it’s level as you go, and continue tracing along the bottom edge all around the alcove.^{[11]
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- This gives you a level line that the underside of the tub’s lip will be at in the alcove for the tub to be level.
4
Screw lengths of 2x4 lumber around the 3 sides of the alcove. These pieces are 2 in (5.1 cm) thick by 4 in (10 cm) wide by default, so just cut them to fit in the alcove. Line 1 long 2x4 up underneath the height line you marked on the back of the wall and drive 3–4 in (7.6–10.2 cm) galvanized screws through the wood into each stud behind it. Do the same for each side wall of the alcove to finish installing the ledger boards that hold the tub level.^{[12]
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- If the studs in the alcove are not exposed, used a stud finder to locate them.
- The boards should be slightly shorter than the length and width of the tub, so they fit underneath the lip.
- If there is drywall over the studs, apply a bead of wood glue along the back of each ledger board as well to help them adhere to the wall nice and securely.
5
Lift the tub into the alcove and set the lip on top of the ledger boards. Get a helper to assist you in lifting and moving the tub. Bend at your knees and lift the tub together with your legs. Lift it up over the ledger boards, making sure the drain hole in the tub is lined up with the one in the floor, and set the tub carefully into place on top of the boards.^{[13]
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- The tub should be supported by the ledger boards and the front edge of the tub should be flush with floor. If the tub has legs on the bottom, they should be sitting on the subfloor underneath it.
- If the tub has adjustable legs, screw them out or in by hand as needed for them to rest on the subfloor of the alcove.
- Lay your level along all edges of the tub and across the middle to verify that it’s completely level.
6
Put a bead of caulk along the edge of the tub where it meets the flooring. Use a caulk gun to squeeze an even bead of silicone caulk along the whole front panel of the tub where it sits flush against the bathroom flooring. Smooth it out with a putty knife and let it dry for at least 1 day for a good seal.^{[14]
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- This only applies if the bathroom flooring is already installed. Otherwise, wait until it is to caulk around the bottom edge of the tub.
- If there is a finished wall behind the tub, apply a bead of caulk along the whole top edge of the tub’s lip as well to seal it.
- If you want to replace an old bathtub, check if the replacement tub fits your space well, and you can move it through all doorways.^{[15]
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- Remove toilets or sinks that may be in the way. Disconnect the drain and the waste-and-overflow unit, and check if you need to replace any damaged parts.^{[16]
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- Since tile damage is possible, you can purchase the replacement tiles beforehand and complete the work quickly.

Warnings

Always refer to the manufacturer’s installation instructions for your specific tub to find the preferred method of installation.

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