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What are the minimum code requirements for residential stairs?
Monday, March 21, 2022
Here are the minimum code requirements for residential stairs:
• The stair riser (vertical piece) cannot exceed 7-3/4-inches in height (IRC R3184.108.40.206)
• The minimum tread (horizontal piece) depth is 10-inches.
• A nosing is required on treads that are less than 11-inches long (IRC - R3220.127.116.11). See When is a nosing required on a stair tread? for full details.
• The steepest stair allowed has 7-3/4-inch risers and 10-inch treads, but the treads require a nosing.
• The longest stair run allowed has a maximum of 147-inches (12’-3”) of vertical height between floor levels or landings.
• Stair headroom cannot be less than 6-feet 8-inches, as measured vertically from the sloped line adjoining the tread nosing or platform on that portion of the stairway (IRC R311.7.2).
• Headroom for spiral stairs can be slightly less, at 6-feet 6-inches (IRC R318.104.22.168)
• A landing is required at the top and bottom of stairs that is at least the width of the stairs and minimum 3-feet deep (IRC R311.7.6), with two exceptions: 1) A landing is not required at the top of an interior flight of stairs, including stairs in an enclosed garage, provided the door does not swing over the stairs [IRC R311.7.6(1)], and 2) A landing is not required where a stairway of two or fewer risers (one tread) is located on the exterior side of an exterior door. (FBC R311.3.2)
• Interior stairs with six or more risers require lighting that is 3-way switched at top and bottom landings. Exterior stairs require lighting at the top landing that is switched from inside home. (IRC R303.7 and R303.8). Go to What is the lighting requirement for stairs? for full details.
• Receptacle outlets are not required at stairs or stair landings.
• Open risers are allowed, as long as “the opening between the treads does not permit the passage of a 4-inch diameter sphere” (IRC 1011.5.5.3).
• A handrail is required for a stair with four or more risers, must be at least on one side of the stair, and 34-inches to 38-inches above the tread (IRC R311.7.8). There are multiple other requirements you can read about at What are the building code requirements for a handrail at stairs?
These requirements are based on the International Residential Code (IRC) and the National Electrical Code (NEC). Other codes and local jurisdiction amendments may be different. Also see Frequently Asked Questions (FAQ) about Minimum Code Requirements
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