Home Improvement Interior Remodel Flooring & Stairs

How to Keep Your Stairs up to Code

Standard Stair Width, Riser Height and Depth, and More

Staircase code requirements not only help you build a safe staircase, but they also assist in building a comfortable staircase that you can use day in and day out, for years to come. Staircase measurements are determined by common practice and by building code, which itself is often informed by generally approved practices. Critical measurements like stairway width, riser height, and tread depth are critical when remodeling or building any home that has multiple levels.

White staircase with a wood and metal railing on wooden steps closeup

The Spruce / Ashley Poskin

Local Codes and Permitting

Not all staircase measurements are universally the same in all parts of the country, though. Be sure to check with your permitting agency about building codes that apply to your locality. Many communities adopt the International Building Code wholesale, while others make modifications. In any case, the local code is what you must follow to pass inspections.

How to Make Sure Your Stairs Meet Code

The following staircase code requirements refer to straight-run stairs. Winding stairs and spiral stairs have several different code requirements.

  1. Measure Staircase Tread Depth

    Measure horizontally from the front edge (or nosing) of a stair tread backwards to the stair riser. This distance must be at least 10 inches. However, the ICC notes that if the steps do not have nosings, and the steps have solid risers, not open risers, the minimum tread depth is 11 inches.

    A step tread is the flat, horizontal surface that you walk on. The tread depth is the distance from the front edge, or nosing (a tread projection that overhangs the riser below), of one step to the front edge or nose of the next step, measured horizontally.

  2. Measure Staircase Riser Height

    With the tape measure, measure the vertical distance of one of the stairs: from the top of one tread to the top of the tread above it. The distance should be no more than 7-3/4 inches.

    This vertical span is the stair riser. A stair riser is the back, vertical part of a step. Staircase riser height translates to the distance you move your foot either up or down from one step to an adjacent step.

  3. Check For Riser Height Consistency

    With the tape measure, check the height of every riser on the staircase.

    It's best if every stair riser is exactly the same height, but they can vary by as much as 3/8-inch and remain within code.

  4. Measure Staircase Width

    Hold the tape measure horizontally and measure from one wall to the adjacent wall, not including handrails. The distance must be 36 inches or more.

    Tip

    Staircase code measurements do allow for some flexibility since most measurements are accompanied by minimums or maximums.

  5. Measure Staircase Headroom Height

    Measure vertically from the top of any stair tread to the lowest point on the ceiling. This distance should be 6 feet, 8 inches minimum.

Staircase Code Requirements

Staircase Width: 36 Inches, Minimum

Staircase width refers to the side-to-side distance if you were walking up or down the stairs. According to the IRC, this distance must be at least 36 inches and does not include handrails.

Staircase Riser Height: 7-3/4 Inches, Maximum

A stair riser is the back, vertical part of a step. Staircase riser height translates to the distance you move your foot either up or down from one step to an adjacent step. This should be no more than 7 3/4 inches.

This code specification was developed to prevent stairs from being too high if walking upstairs or too low if descending. Additionally, the riser measurement of all of the treads should be as close as possible to identical. The greatest riser height within a flight of stairs cannot exceed the smallest by more than 3/8 inch. A stairway in which there is a noticeable variation between the risers is a safety hazard.

Open Risers

If the stairs have open risers, the open space between the steps cannot be large enough to allow a 4-inch sphere to pass through. In other words, the space must be slightly less than 4 inches high.

Staircase Tread (Run) Depth: 10 to 11 Inches, Minimum

Staircase risers should be adequately deep to allow a majority of your foot to have enough room to rest on the stair. Stair tread depth is more of an issue for descending, rather than ascending, stairs. 

The tread measurement of every tread in a stairway should be as close as possible to identical. The greatest tread depth within a flight of stairs cannot be more than 3/8 inch larger than the smallest tread depth.

Nosing Projection

Nosings must project at least 3/4-inch and no more than 1-1/4 inches beyond the riser below. The largest nosing projection cannot be more than 3/8-inch greater than the smallest nosing projection.

Staircase Headroom: 6 Feet, 8 Inches, Minimum

Anyone walking up or down the stairs should have plenty of clear headroom without having to duck down. 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.

Staircase Landings and Lighting

Staircase Landings

Every staircase should have a landing at the top and bottom. The width of the landing, measured perpendicular to the direction of travel, must be no less than the width of the staircase. The minimum depth, measured in the direction of travel, is 36 inches.

Staircase Lighting

The treads and landings of all straight-run staircases should have an artificial light source capable of lighting the treads and landings to no less than 11 lux (approximately 1-foot candle). For any staircase that has six or more risers, there must be a wall switch at each floor level to control the light source.

Staircase Terms

  • Stringer: The stringer is the entire sawtooth-shaped member upon which risers and tread rest. You will need at least 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 that 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. The board that encloses the back of the step is also called a riser.
  • Tread: The tread is the horizontal section of each stair, sometimes called the run. This is the surface that the user steps on.
  • Landing: A landing is a platform between two flights of stairs. It is also the approach space at the top and bottom of the stairs.
  • Nosing: The section of the tread that overhangs the riser below.
  • Staircase width: Width refers to the length of risers and treads from side to side. For code requirements, the minimum staircase width is the horizontal dimension between the sidewalls of a staircase, measured above the handrail(s).
  • Headroom: Headroom is the vertical dimension from the stair treads to the ceiling directly above. It is measured from a sloping imaginary line that connects all of the stair nosings.