Minimum Stairway Width

Okay here's another one of those tricky stairway building codes that I tried to simplify.

The minimum width for any stairway is 44 inch, for any buildings with more than 50 occupants. This building code might apply to large public buildings that would require people to pass each other as they walk up and down the stairs, without being inconvenienced.


Reference: 2012 International Building Code - 1009.4 page 253

The minimum width for any stairway that has less then 49 occupants is 36 inches. This would include individual dwellings or houses.

I simplified the verbiage used in most building codes, so that almost anyone could understand it. When you read the building codes in the I.B.C., they're confusing and hard for me to validate.


There are other exceptions to and for this building code, but these are the basics.

I suggest that you check out the maximum hand rail projection page, because I also found a building code that requires a minimum distance of 36 inches in between handrails and this would be a problem for anyone planning on building a stairway smaller than 45 inches wide.

Yes, to answer your question, these building codes are confusing and can only be interpreted by your local Building Department officials.


Decorative trim and skirt boards can't protrude more than an inch and a half into a stairway.

To measure the minimum clear width of any stairway, measure from finished wall to finished wall. In the picture above, this measurement would be from the right side of the finished drywall or wallboard to the left side.