Residential Bathroom Code Requirements & Design Tips

If you're thinking about redesigning your bathroom, you're not alone. Bathroom remodels are one of the top home-improvement projects in the U.S. And with good reason. A well-designed bathroom can have a tremendous impact on your enjoyment of your home.

There are, however, many considerations that go into designing a bathroom that not only looks great but is ergonomic and safe. Bathroom design may seem simple enough, given that it's usually a small space, but size can be deceiving. I encourage you to seek the help of an experienced interior designer to ensure that your bathroom is perfectly designed to your needs and follows best practices.

Read on for 17 of the most essential bathroom layout guidelines and code requirements. I'll be delving into dimensions, spacing between walls and fixtures, ceiling height, and much more. To give you the full picture, I'll be covering residential bathroom building codes, as well as bathroom design recommendations from the National Kitchen and Bath Association that serve as excellent rules of thumb.

What's the difference between building codes and NKBA guidelines?

Building codes are the law

Building codes are an area's official rules on building safety. Anyone tackling a construction project (including a homeowner doing DIY work) is legally required to follow these rules. For all but the most minor cosmetic building projects, city inspectors will check to make sure that building codes were followed.

International building codes keep things uniform

Most cities and municipalities choose to adopt a set of universal building codes for residential construction that are developed and updated by the International Code Council (ICC). Collectively, these are referred to as the International Residential Code (IRC). Municipalities can they layer more specific rules on top of the IRC or otherwise amend certain rules.

When planning a project, the IRC is a good starting point, but always check your local codes. Here in Seattle, for instance, we have the Seattle Residential Code (SRC) that includes many amendments to the IRC.

The NKBA offers best practices for bathroom design

The National Kitchen and Bath Association (NKBA) publishes planning guidelines to help interior designers create bathrooms that are both functional and safe. These are not legal requirements, like building codes, but they are extremely helpful in ensuring that a bathroom is not only safe but enjoyable to use. NKBA members, like CRD Design Build, refer to these guidelines regularly, as well as our own experience, to design bathrooms that are as functional as they are beautiful.

Bathroom Building Codes and NKBA Recommendations

While you always have to follow your local code, you'll find that NKBA guidelines either take the code and build upon it or offer recommendations on which the code is silent. Below is a summary of what I consider 16 of the most important NKBA bathroom design guidelines. I also included the relevant codes for comparison.

1. Entry door openings

IRC

• The  IRC doesn't mention anything about the minimum size of bathroom doors.

NKBA

• The minimum size of a bathroom doors should be at least 32" wide. 
• For 32" of clear width, the door width (from jamb to jamb) should be 34".
• Since 34" is not a standard door width, most designers spec a 36" door, which is not usually a special order.
• To meet ADA universal design standards, plan on 34" of clear opening, or a 36" door.
• The NKBA makes an exception for situations where it's impossible to fit a 34" door, allowing a 24" door in those circumstances.  
• NOTE: If you are remodeling an existing bathroom, most cities will allow the existing door width to remain, even if they have a local code in place requiring a wider door. However, if the location of the door is moved, it usually will have to follow the code.

2. Door interference

IRC

• Again, the IRC doesn't have any requirements relating to doors bumping into each other in the bathroom or a recommended minimum size of a bathroom door.

NKBA

• Good design dictates that the entry door doesn't bump into the shower door or cabinet doors or drawers.
• NOTE: A good way to ensure that you can meet this guideline, even in a small bathroom, is to design an entry door that swings out into the hall instead of into the bathroom.

3. Ceiling height

IRC

• Bathrooms must have a minimum ceiling height of 80" in front of fixtures, which is less than the 90" ceiling height  required in most rooms.
• The 30" x 30" area in front of a shower head must also be 80" in height.

NKBA

• The NKBA doesn't have anything to add to the IRC requirement in this case.
• The recommended ceiling height over sinks and other fixtures (basically, wherever you can't walk) is only 60".

4. Clear floor space

IRC

• At least 21" is required between the toilet, bidet, and sink and any opposite wall or other fixture.
• At least 24" is required in front of the shower  entry.

NKBA

• Building code only requires 21" of floor space in front of the toilet or sink, but that feels quite cramped, so the NKBA recommendation is 30".
• NOTE: If you are remodeling an older bath that's just 5' wide, a smaller 21" or 24" clear space may be all you can fit. A wall-hung toilet can help free up space, however.

5. Sink spacing

IRC

• The minimum distance from the centerline of the sink to a wall is 15".
• There must be 4" between  the edge of a free-standing or wall-hung sink and the wall. (This makes it easier to clean between the edge of the vanity and the wall.)

NKBA

• The NKBA recommends 20" from the center of the sink to the closest wall or other tall obstacle.   This extra bit of elbow room makes it more comfortable to wash your hands.

6.   Distance between double sinks

IRC

• The distance between the centerlines of two sinks  must be at least 30".
• Freestanding or wall hung sinks should have at least 4" of space between them.

NKBA

• The NKBA recommends at least 36" between the centerlines of two sinks.  When in doubt, go with smaller sinks so there is more room in between. This extra space ensures that you won't bump elbows with the person using the sink next to you.

7.   Vanity height

IRC

• No code requirement for vanity height.

NKBA

• Vanities should be 32" - 34" in height.  In the old days, 32" vanities were the norm, with the goal of accommodating both kids and adults. Nowadays, standard practice is to customize them to be comfortable for adult users. Kids can use stools, which can even be on a pull-out mechanism built into the vanity.

8. Countertop corners

IRC

• The IRC is silent on this one.

NKBA

• Countertop corners shouldn't be sharp.
• Chamfered or rounded corners should be installed for safety.

9. Shower size

IRC

• The minimum interior shower size is 30" x 30" or 900 square inches, in which a disk of 30" in diameter must fit.  (In most places, the shower head must also be inside this imaginary disk.)

NKBA

• The code minimum is 30" x 30", but 36" square is much more comfortable.

10.   Grab bars

IRC

• There are no international code prescriptions for grab bars.

NKBA

• Plan grab bars.  Even if you don't need them now, grab bars (or blocking within the walls) should be installed 33" - 36" above the floor in the shower.

11. Non-slip floors

IRC

• No international code requirements for flooring type.

NKBA

• The NKBA recommends non-slip floors.  Don't install any slippery flooring in your bathroom (including your shower floor). Ceramic tile floors should have a coefficient of friction (COF) rating of at least 0.5 when wet.

12. Toilet placement

IRC

• A minimum distance of 15" is required from the centerline of a toilet  to any bath fixture, wall, or other obstacle.

NKBA

• Give your toilet some space. The distance from the centerline of your toilet bowl to the nearest wall or obstacle should be at least 18".  Only use the 15" minimum code requirement if you have a very small bathroom and can't accommodate the extra distance.

13. Toilet compartments

IRC

• The minimum size for a separate toilet compartment is 30" by 60".
• Again, there are no guidelines for the minimum size of a bathroom door.

NKBA

• When it comes to toilet compartments (also known as water closets or WCs), the NKBA recommends a larger space of 36" x 66".
• If you have a swing-out or pocket door, you can use these minimum dimensions. If the door swings in, add the width of the door to the depth of the WC.

14. Bathroom accessories

IRC

• The IRC doesn't require the placement of any accessories.

NKBA

• The NKBA recommends the placement of  accessories with an eye to ergonomics. 
• A mirror should be placed over the sink with eye height in mind, the toilet paper holder should be 8" - 12" in front of the edge of the toilet bowl, and towel holders and soap dishes should be conveniently located.

15. Ventilation

IRC

• Minimum ventilation for the bathroom is to be a window of at least 3 sq. ft. of which 50% is operable, or a mechanical ventilation system of at least 50 cubic feet per minute (cfm) ducted to the outside.

NKBA

• An exhaust fan that is vented to the outside of your home should be placed in each bathroom.
  • If your shower compartment or WC is fully enclosed, they are considered their own room and should have their own exhaust fans.

See also: A Practical Guide to Window Placement

16. Heating

IRC

• All bathrooms should have an appropriate heat source to maintain a minimum room temperature of 68° Fahrenheit (20° Celsius).

NKBA

• The NKBA recommends that the bathroom should be about 10 degrees warmer than the rest of the house when someone is bathing.
• Consider installing a supplemental heat source in the bathroom if needed.

Putting it all together

Bathroom design and space planning is often not given the thought it deserves. If you are planning to remodel your bathroom or add a bath to your home, these 16 rules of thumb are a great place to start. But don't stop here. I encourage you to speak to an experienced interior designer to truly dial in your new bathroom space (and ensure you don't run afoul of your local building code). It's amazing how much a thoughtfully planned bathroom can add to your enjoyment of your home and quality of life.

My interior design colleagues and I here at CRD Design Build would be happy to discuss your bathroom remodeling plans. Please feel free to  drop us a line  to discuss your dreams for your bathroom space. We would love to be of service.