Toilet Rough In Dimensions to Consider When Replacing a Toilet

Installing or replacing a toilet may appear to be a difficult task. With various styles and types to choose from, it is simple to get carried away by the options. 

Luckily, with a couple of basic toilet rough in dimensions, you can select and configure a lavatory that will perfectly suit your bathroom, be it in your office, home, or commercial establishment.

4 Toilet Rough In Dimensions to Measure

If you want to rough in your toilet, there are four crucial rough in dimensions you have to know:

  • The distance between the bowl and the back of the wall where you need to set your toilet frame.
  • The required space from right to left.
  • The space you should leave in front of your toilet bowl.
  • The location to install the cold-water connection line.

With no further ado, let us begin with each of these dimensions.

1. The Distance Between the Toilet’s Bowl and the Back Wall

You should set the middle of the water gasket just 12 inches from the end of the back wall. Also, don’t take your measurements from the foundation molding! This dimension should be taken from just the beginning of the completed back wall.

Now, if you are taking measurements from stud walls, do not forget to take the width of your back wall into account. The most prevalent drywall thickness is ½ inches, and if this is the scenario, the dimension ought to be 12 ½ inches. Moreover, the measurements should begin from the end of the stud wall.

It is crucial to note that this dimension is typical lavatories with a 12-inch rough-in. The specification sheet of your lavatory contains a detailed description of these dimensions, but the most common rough-in size for a toilet is 12 inches.

It is important to be aware that lavatories are also available in other rough-in sizes, such as:

  • 8 inches
  • 10 inches
  • 14 inches

If you are going to replace your lavatory and realize that the middle of the gasket is only ten inches away from the end of the back wall, then you do not need to move the gasket. All you have to do is purchase a bathtub with a rough-in measurement of ten inches.

Assume you are roughing in a lavatory, and a floor joist gets in your way. You might be smart enough to avoid the framing by using a varying toilet rough-in. Being aware of such information would help you save both money and time. 

Wall-mounted toilet
Wall-mounted toilet

2. The Distance Between the Middle of the Lavatory and Surrounding Fixtures

The lavatory should be at least 15 inches from any neighboring fixture or back wall from both sides of the toilet. Take the measurement from the middle line of the toiled and not from its outside edge. 

It is also important to measure the actual distance before installing the toilet. For instance:

  • If your bathroom vanity is in front of your lavatory, provide a clearance space of 13 inches.
  • If your bathtub is in front of your lavatory, allow a clearance space of 15 inches.
  • If a back wall is in front of your lavatory, create a clearance space of 15 inches.

Remember to include the width of your back wall if you are taking measurements in front of a stud wall. A good example is to assume that you are assembling ½ inch drywall with a 3/8-inch mosaic tie. Find the sum and then add the total width of the wall to the needed 15 inches.

According to building codes, there is minimum spacing required between neighboring fixtures and the middle of the toilet. The distance between the lavatory and the back wall is specified during the design stage, and the architects’ blueprints must reflect this.

The Americans with Disabilities Act (ADA) restricts building regulations in commercial and public places to allow disabled individuals easier access to the toilet. The distance between the middle of the lavatory gasket and the toilet framing must be 12-1/2 inches. 

However, the least space towards the edge rises to 18 inches for either side of the toilet. That should be from the toilet’s middle line to the edge of the wall. Building surveyors strictly enforce ADA specifications that entail minimal clearance around a toilet unit.

3. The Distance Between The Toilet and Any Obstruction In Front of the Bowl

Your available local plumbing code determines this clearance. Typically, you will require a minimum of 21 inches of clearance if your specific municipality follows the International Plumbing Code (IPC). On the other hand, you will require a minimum of 24 inches of clearance if your specific municipality follows the Uniform Plumbing Code (UPC).

This distance is taken just from the edge of the lavatory towards the obstruction, and round toilet bowls often provide adequate clearance than their elongated counterparts. Examples of obstruction that might be present include:

  • A door
  • Walls
  • A different drainage fitting

So perhaps you are curious to know if you still require a clearance of 21 inches next to the lavatory when your washroom door is kept open. No, it is not necessary. The main aim of the clearance plumbing code is to provide ample space for you to use the lavatory more comfortably. 

Fortunately, the door normally gets shut while using the toilet. And provided you have 24 or 21 inches of clearance once the door gets closed, you should be fine. 

Round bowl toilet
Round bowl toilet

#4. Where to Install the Cold Water Supply Pipe

When installing a cold water supply pipe, you should make sure to measure 6 inches towards the left from the middle line of the bathtub flange and measure 7 inches just above the floor surface. This is the most appropriate height as it clears the modeling sizes of the toilet base.

The water pipe often comes lower, necessitating trimming. Undoubtedly, this normally results in an ugly appearance. Therefore, 7 inches above the floor surface provides ample space for an emblem and base cut up to 5.25 inches.

It is usually fine for plumbers to go 6 inches above the floor surface. If you have a 5 ¼ inches base molding installed, you will need to reduce the trim.

How to Measure a Toilet Rough-in Size

When you talk about toilet rough-in, a regular toilet refers to one that is assembled against the washroom wall and has a floor outlet vent. These are by far the most popular types of lavatories. To get rough in dimensions, you require to take the measurements of the length between the completed back wall of the toilet and the middle of the drainage pipe. 

It’s very important that you take the measurements from the edge of the completed wall. If you take measures starting from the flanged wall, a ½ inch plasterboard will most likely get assembled. As a result, expect an approximate error of almost ½ inch. 

Thus, if your rough measurements read 12.5 inches, the precise rough-in measurement from the flanged wall will be 12 inches. This also applies for lavatories with 14 inches or 10-inch rough-ins, even though it is still critical to take measurements from the completed wall rather than the molding.

Standard toilet rough-in
Standard toilet rough-in

How to Measure the Rough-in for a Corner Toilet

To determine the rough-in dimensions for a corner toilet, measure the length between the completed wall of any of the two adjacent walls and the middle of the drainpipe. Unlike a regular toilet, the rough-in dimensions of a corner toilet cannot be measured from the completed wall to the lavatory bolts. Most corner lavatories toilets, like regular toilets, have a 12-inch rough-in.

You may have to relocate the flange prior to installing the corner toilet if you have additional tilling on the washroom wall. If the width of your bathroom wall increases by more than ½ inches, you will most likely need to relocate the flanges. Because the ½ inch should be from both exterior walls, the length from the corner will be approximately 17 inches. If you do not want to relocate the flanges, you can go with a 10-inch rough-in lavatory.

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Rough-in for corner toilet and wall-hung toilet

Wrapping Up

As mentioned earlier, installing a toilet necessitates a great deal of precision, know-how, and good handiwork. Installing too far from the molding is the last problem you want to have while roughing in a toilet. Despite the high popularity of 12-inch rough-in toilets in today’s market, 14-inch rough-ins have their advantages. Sometimes, it is necessary to minimize the space occupied at the back of the toilet tank. Hopefully, you’ve learned everything you need to know about the most important toilet rough in dimensions to be aware of before roughing in a lavatory.


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