Critical measurements such as standard stairway width, riser height, and tread depth are not a matter of guesswork when you are remodeling or building a home. Staircase measurements are determined by common practice and by building code, which itself is often informed by generally approved practices. These rules are aimed at making stairways as safe as possible, so they should never be ignored or bypassed.
At the same time, staircase code measurements do allow for some flexibility, since most measurements are accompanied by minimums or maximums. A prime example is standard stair width. Code states that staircases must be three feet wide or wider. As long as the three-foot width standard is met, you can expand the stairs' width as far as you wish.
Not only do suggested standards help you build a safe staircase, they assist in building a comfortable staircase that you can use day in and day out, for years to come. Not all staircase measurements are universally the same in all parts of the country, though. Be sure to check with your local permitting agency about building codes that apply to your structure. Many communities adopt the International Building Code wholesale, while others make modifications.
Staircase Width: 36 Inches, Minimum
Staircase width refers to the side-to-side distance if you were walking up or down the stairs. This distance must be at least 36 inches and does not include handrails. Handrails will narrow that distance.
Stairs that are too narrow are a hazard in many ways. Narrow stairs make it more difficult to carry items up and down the stairs. Awkward positioning of these items may lead to falls. Most importantly, stairs that are not wide enough are a fire hazard, as they might impede escape.
Staircase Riser Height: 7 3/4 Inches, Maximum
Staircase riser height means that the distance you move your foot either up or down from one stair to an adjacent stair should be no more than 7 3/4 inches.
This piece of staircase code was developed to prevent stairs from being too high if walking upstairs or too low if descending. Additionally, the riser measurement of each tread in a stairway should be as close as possible to identical. A stairway in which there is noticeable variation between the risers is a safety hazard.
Staircase Tread (Run) Length: 10 Inches, Minimum
Staircase tread is the flat, horizontal distance from the edge of the stair to the back part where it stops (called the riser). This distance should be at least 10 inches long.
Staircase risers should be adequately deep to allow a majority of your foot to have enough room to rest on the stair. Stair tread length is more of an issue for descending, rather than ascending, stairs. Further, the tread measurement of each tread in a stairway should be as close as possible to identical. A stairway in which there is noticeable variation between the treads is a safety hazard.
Staircase Headroom: 6 Feet, 8 Inches, Minimum
At any point on the staircase, a user should have a full 6 feet, 8 inches minimum vertical distance between the top of the stair tread and the bottom of the ceiling.
Anyone walking up or down the stairs should have plenty of clear headroom without having to duck down. Low headroom may result in staircase users hitting their head on their way down the stairs. This may also lead to a user looking away from their path in order for their head to clear the obstruction.
Common Stairway Terms
- Stringer: The stringer is the entire sawtooth-shaped member upon which risers and tread rest. You will need two per staircase. Some utility stairways, such as basement stairs or deck stairs, may not use a sawtooth stringer design. Instead, they may use solid side stringers which anchor the treads using metal connectors.
- Riser: A riser is the vertical measurement of each stair. Risers can either be enclosed or left open, as in deck stairs or basement stairs.
- Tread: The tread is the horizontal section of each stair, sometimes called the run. This is the section that the user steps on.
- Staircase Width: Width refers to the measurement of risers and treads from side to side as if you were walking up or down the stairs.
- Headroom: Headroom is one dimension that often gets ignored. Imagine drawing a sloped line along the noses of each tread. The vertical measurement above this sloped line is the headroom.