Minimum Interior Door Opening Size

[Bruce Ramsey]

IRC specifies that the main egress door must be 3' wide and 6'8" tall, hinged on one side. But I could not find any minimums regarding interior doors or doors to bathrooms.

16 year old house. Half bath is located under stairway. As a result the stairs intrude into the path of the door way. Dumb design. There is a pantry closet to the right of the bathroom that could be sacraficed to allow the bath to expand so the door could be relocated and would not be blocked by the stairs. Anyway...

Are there any IRC references to the minimun opening size to interior rooms, the size of doorways, or access to bathrooms?

[Jerry Peck - Codeman]

Hi Bruce,

IRC specifies that the main egress door must be 3' wide and 6'8" tall, hinged on one side. But I could not find any minimums regarding interior doors or doors to bathrooms.

This is why you could not find any sizes for "other doors" than the required egress door:

From the 2006 IRC. (underlining and bold are mine)
- R311.4.2 Door type and size. The required exit door shall be a side-hinged door not less than 3 feet (914 mm) in width and 6 feet 8 inches (2032 mm) in height. Other doors shall not be required to comply with these minimum dimensions.

Even the 2006 IBC includes exceptions to the required door widths stated in it:
- 1008.1.1 Size of doors. The minimum width of each door opening shall be sufficient for the occupant load thereof and shall provide a clear width of not less than 32 inches (813 mm). Clear openings of doorways with swinging doors shall be measured between the face of the door and the stop, with the door open 90 degrees (1.57 rad). Where this section requires a minimum clear width of 32 inches (813 mm) and a door opening includes two door leaves without a mullion, one leaf shall provide a clear opening width of 32 inches (813 mm). The maximum width of a swinging door leaf shall be 48 inches (1219 mm) nominal. Means of egress doors in a Group I-2 occupancy used for the movement of beds shall provide a clear width not less than 41.5 inches (1054 mm). The height of doors shall not be less than 80 inches (2032 mm).
- - Exceptions:
- - - 1. The minimum and maximum width shall not apply to door openings that are not part of the required means of egress in Group R-2 and R-3 occupancies.
- - - 2. Door openings to resident sleeping units in Group I-3 occupancies shall have a clear width of not less than 28 inches (711 mm).
- - - 3. Door openings to storage closets less than 10 square feet (0.93 m2) in area shall not be limited by the minimum width.
- - - 4. Width of door leafs in revolving doors that comply with Section 1008.1.3.1 shall not be limited.
- - - 5. Door openings within a dwelling unit or sleeping unit shall not be less than 78 inches (1981 mm) in height.
- - - 6. Exterior door openings in dwelling units and sleeping units, other than the required exit door, shall not be less than 76 inches (1930 mm) in height.
- - - 7. In other than Group R-1 occupancies, the minimum widths shall not apply to interior egress doors within a dwelling unit or sleeping unit that is not required to be an Accessible unit, Type A unit or Type B unit.
- - - 8. Door openings required to be accessible within Type B units shall have a minimum clear width of 31.75 inches (806 mm).

Thus, while the IRC does not specifically disallow reduction in height for a doorway to below 80 inches (6 feet 8 inches) or even below 78 inches (6 feet 6 inches), a correlation for similar areas to the IBC does specifically disallow a reduction in height below 78 inches (6 feet 6 inches) while allowing a reduction in width.

Therefore one could infer that the minimum allowable height is 78 inches *for the given width of the door*, or, stated another way, the height of the door needs to be 78 inches for the width of the door.

Here is another way to address it: "ceiling height".

From the 2006 IRC.
- R305.1 Minimum height. Habitable rooms, hallways, corridors, bathrooms, toilet rooms, laundry rooms and basements shall have a ceiling height of not less than 7 feet (2134 mm). The required height shall be measured from the finish floor to the lowest projection from the ceiling.
- - Exceptions:
- - - 1. Beams and girders spaced not less than 4 feet (1219 mm) on center may project not more than 6 inches (152 mm) below the required ceiling height. (Jerry's note: 7 feet less 6 inches equals 6 feet 6 inches or 78 inches, the minimum height of a door in the exceptions allowed in the IBC.)
- - - 2. Ceilings in basements without habitable spaces may project to within 6 feet, 8 inches (2032 mm) of the finished floor; and beams, girders, ducts or other obstructions may project to within 6 feet 4 inches (1931 mm) of the finished floor.
- - - 3. For rooms with sloped ceilings, at least 50 percent of the required floor area of the room must have a ceiling height of at least 7 feet (2134 mm) and no portion of the required floor area may have a ceiling height of less than 5 feet (1524 mm).
- - - 4. Bathrooms shall have a minimum ceiling height of 6 feet 8 inches (2036 mm) over the fixture and at the front clearance area for fixtures as shown in Figure R307.1. A shower or tub equipped with a shower head shall have a minimum ceiling height of 6 feet 8 inches (2036 mm) above a minimum area 30 inches (762 mm) by 30 inches (762 mm) at the showerhead.

The end result is that there are several code references establishing a minimum overhead height of 6 feet 8 inches (80 inches, which is standard door height) with a limited number of exceptions allowing that height to decrease to 6 feet 6 inches (78 inches) and only one exception to reduce the overhead height to 6 feet 4 inches, which is for limited to a basement and "beams, girders, ducts", etc.

Cutting off a doorway at a 45 degree angle increases the odds of someone hitting their head to even greater than if the entire opening had been reduced to the lower height, which even the builder/remodeler/homeowner who did that realized was just plain dumb, ... so they did it like shown in the photo.

This is one of those cases where code skirts the issue, showing all the heights for other things which would offer similar head banging experiences, but does not address that specifically, leaving to common sense not to do something that dumb.

[Bruce Ramsey]

Thanks for the research.

I understand the code cannot anticipate every dumb thing a builder/architect can do. Technically the doorway is 6.8", its just the ceiling behind the doorway that is goofy. The exception regarding sloped cielings over toilets creates an exception to allow for the ceiling height. Within code but still goofy. Saftey hazard, skull buster, head banger, by whatever name you call it, it is just plain dumb. OF course the architect will say a creative way to squeeze the most out of space within the footprint.

[Jerry Peck - Codeman]

Hi Bruce,

The exception regarding sloped cielings over toilets creates an exception to allow for the ceiling height.

I'm not following you there.

The minimum headroom over a plumbing fixture is 6 feet 8 inches, just like a standard height doorway.

I do agree that the IRC SHOULD address the minimum height and minimum width of a doorway, with an exception for storage areas with lower ceiling. Such as if a storage area has a 4 foot ceiling, installing a 6 feet 8 inch door makes no sense, so the door could the the height of the highest low ceiling less 2 inches (to allow for head jamb and trim), and the width could be a minimum of 24 inches except for limited use closets of 24 inches width, which could be allowed to reduce the minimum door width to 20 inches.

There could be some good usable standards developed, and some good sensible exceptions.

In the case of your photo, the door could be allowed to be down to the lowest height of the slope which crosses the door, meaning that you know it is storage area and the door, while shorter, is level across the header with no ceiling obstruction beyond it.