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Tub Rough Opening Too Big or Small: A Complete Guide

Without a proper rough-in space a tub will not fit properly. Also, too much rough opening will create a gap between the wall and the tub. But sitting around isn’t going to solve the problem. You’ve to take the necessary steps as soon as possible. 

But what to do if the tub rough opening is too big or small? 

The standard rough-in dimension for a bathtub is 60-¼”. But if there’s a gap, you can attach furring strips to the stud wall. You can also apply some cement or plywood. Finally, if the rough-in space is too small, you have to tear the stud wall down or replace the bathtub. 

That was nothing but just a preview of the discussion. Read along if you want to fix your faulty tub rough opening. 

Let’s stop beating around the bushes and head right in:

The Standard Rough-In Dimensions For Your Bathtub

Rough-in dimension means the total length of space between one wall to another. This definition may vary for other installations. 

The standard size of bathtubs is 5 feet or 60 inches. But if the rough-in dimension is 60inches, the bathtub might not fit. 

At least, it’ll be really hard to fit it. The bathtub is going to get scratched regardless. This is something you don’t want at all. 

Also, you may have to retile the shower if you’re installing a new bathtub. Fortunately, it doesn’t take that long to retile the shower

That’s why experts keep an extra quarter of an inch gap while framing for bathtubs. There are a lot of bathtubs of different sizes. 

Here are some common bathtubs and their recommended rough-in dimensions: 

  • Alcove Bathtubs: The alcove bathtubs are pretty common and quite luxurious. The rough-in length for this bathtub will be 60-¼”. The rough-in width for this bathtub will be 32-¼”. 
  • Whirlpool Bathtubs: The whirlpool bathtubs are oval. So, take the highest diameter from the center then add ¼”. The length and width of the rough-in are usually 60-¼” and 32-¼” or 36-¼” respectively.
  • Cornered Bathtubs: For a cornered bathtub, you have to add space only once. First, place the bathtub in the corner and measure it. Normally, it takes around 60-⅛” inches in both width and length. If you want to add a stud wall, keep ⅛” extra space for it.  

Hopefully, this information will help you rough frame a bathtub.

How To Fix A Bigger Rough-In Space 

That was about how to frame a proper rough-in for a bathtub. But what to do if the rough-in is already too big for the bathtub? Well, in that case, you’ve to make adjustments by adding new stud walls. 

Also, make sure the gap between the tub and floor is optimal. Otherwise, you’ll have to close the extra gap between floor tile and tub

This is a pretty easy method when it comes to leveling the stud walls. But there are some calculations. You might have to do them a couple of times till it gets fixed. 

Now, gather these necessary tools and get started:

  • 2×4 Lumber Wood
  • Wood Cutter 
  • Measuring tape 
  • Frame Ruler 
  • Nail Gun or Hammer 

Step #1: Take Measurements of the Extra Space

First, place the bathtub and connect it to one corner. Now, there are multiple stud walls in a frame so take measurements for all of these. 

Each of these walls needs to be leveled properly. For that, you’ll need the same amount of wood pieces. They’ll be attached to the stud walls later. 

Step #2: Cut the Lumber into Pieces

Take a frame ruler and divide the wood into pieces. After that, take the woodcutter and a 2-5” wood to cut it. 

The length of the wood has to match the height of the wall. 

Step #3: Attach the Stud Walls 

Now, you have all the pieces and it’s time to hammer it. When finished, take the frame ruler and hold it against the stud walls. 

Check for any gaps for all the stud walls. If there’s a gap, just take the measuring tape again and measure it.

Repeat the process and your wall will be a perfect fit for the bathtub. By the way, if the extra space is too small, you can add a cement backer board to the stud wall

How to Fix A Smaller Rough-In Space

There are two ways to fix a smaller rough-in space. Both of them require quite a sum of money and a lot of time.  

Method #1: Replace or Trim the Stud Walls

First, you can replace the stud walls and make new ones. For this, you’ve to undo one of the frames. While making a new stud wall, be sure to calculate properly. 

Or you could trim down a stud wall if replacement is too hard to get. It takes a while to do it but the end result is what matters the most. 

Method #2: Get a Bathtub Replacement 

Another way is to get a replacement for a bathtub. There are multiple sizes available for almost all types of bathtubs. 

There are also smaller bathtubs such as 48 inches to 54 inches. But you might have to order them as they might not be available at all times. 

By the way, you may also have to tile around the floor drain if the sizes are different.  

Anyways, if these seem too time-consuming to you, be sure to hire a professional. 


Question: What is a good size for a soaking tub?

Answer: Average soaking tubs come in 60 inches long and 32 inches wide. But there are multiple variations and you can choose whatever you like. 

Question: How far off the wall should a tub drain be?

Answer: A tub drain should always be 12 inches far from the wall. This gives enough space for a drain installation and proper flow. 

Question: What is the standard width of a bathtub?

Answer: Almost all bathtubs have a width of 30 inches. This is considered optimal as it doesn’t take too much space. 


That is all you can do if your tub rough opening is messy. We hope that this information and these procedures will help you fix the issue. 

Last but not least, best of luck!