South Carolina Residential Stair Code: Risers, Rails, Landings

The South Carolina residential stair code is the 2021 International Residential Code (IRC), which the state’s Building Codes Council adopted effective January 1, 2023.¹ It fixes the exact numbers for risers, treads, handrails, guards, landings, headroom, structural loads, and lighting in one- and two-family homes. Local building departments enforce those rules through permits and inspections, so getting a dimension wrong on paper or in the field usually means rework before a certificate of occupancy is issued.

Riser and Tread Dimensions

Risers can be no taller than 7 3/4 inches.² South Carolina carries one state-specific exception: masonry stairs may have risers up to 8 inches.³ Treads must be at least 10 inches deep, measured horizontally between the front edges of adjacent treads.

Uniformity is enforced as tightly as the individual measurements. Within a single flight, the tallest riser cannot exceed the shortest by more than 3/8 of an inch, and the same 3/8-inch tolerance applies to tread depths.² Small variations between steps are enough to cause falls once a person has settled into a walking rhythm, and inspectors verify these with precision tools.

Nosings

When treads are less than 11 inches deep, which describes most residential stairs built to the 10-inch minimum, the leading edge of each tread must project past the riser below by at least 3/4 inch and no more than 1 1/4 inches. A curved or beveled nosing edge cannot have a radius greater than 9/16 inch. Projections must be uniform along the flight to within 3/8 inch. Treads 11 inches deep or more don’t need a nosing at all.

Open Risers

Open-riser stairs are allowed, but the gap between treads must be small enough that a 4-inch sphere cannot pass through it.

Stairway Width and Headroom

Stairways must be at least 36 inches wide, measured above the handrail height and below the required headroom. Handrails may project up to 4 1/2 inches from each side, so the clear width at handrail level narrows to 31 1/2 inches with one handrail, or 27 inches with handrails on both sides.

Headroom must be at least 6 feet 8 inches throughout the stairway and at landings, measured vertically from the sloped line connecting the tread nosings up to any ceiling or obstruction above.⁴ In older homes with low floor-to-floor heights, this is the requirement stair renovations most often collide with, and the fix usually means raising framing above or adjusting the stair’s pitch.

Handrails

Any stairway with four or more risers needs a handrail on at least one side.⁵ The top of the handrail must sit between 34 and 38 inches above the nosing line.

The rail must be continuous for the full length of the flight, from directly above the top riser to directly above the bottom riser. Ends must return to the wall or terminate in a newel post or safety terminal, so nothing can catch on an exposed end. Newel posts are allowed to interrupt continuity at turns, landings, and winder transitions, and a volute or turnout can terminate the rail over the lowest tread.⁶

Two graspability profiles are recognized. Circular Type I handrails must have an outside diameter between 1 1/4 and 2 inches. Non-circular Type I rails need a perimeter between 4 and 6 1/4 inches. Type II handrails, with a perimeter over 6 1/4 inches, must have a finger recess on each side that starts within 3/4 inch of the tallest point and provides at least 5/16 inch of depth.

Guards and Baluster Spacing

Guards prevent falls from elevated walking surfaces. On porches, balconies, and landings, guards must be at least 36 inches high, measured from the walking surface. Along the open side of a stairway, guards may be as low as 34 inches, measured from the nosing line. Where a stair guard doubles as the handrail, its top must fall inside the 34-to-38-inch handrail range.⁷

Baluster spacing follows the 4-inch sphere rule: openings from the walking surface up to the required guard height cannot allow a 4-inch sphere to pass through. Two exceptions apply on stair guards. The triangular opening formed by the riser, tread, and bottom rail may be as large as 6 inches. Other openings on the open side of the stair are held to 4 3/8 inches rather than 4.⁸

Landings

Every stairway needs a floor or landing at the top and the bottom of the flight.⁹ One exception: an interior flight (including garage stairs) doesn’t require a landing at the top so long as no door swings out over the stairway.

For a straight-run stairway, the landing must be at least 36 inches deep in the direction of travel, and it cannot be narrower than the stair it serves.⁹ No single flight can rise more than 12 feet 7 inches between floor levels or landings.¹⁰ Standard 8- and 9-foot ceilings easily fit under that number; tall foyers and split levels are where intermediate landings start becoming necessary.

Spiral and Winder Stairs

Spiral and winder stairs have their own dimensions because the geometry is different from a straight flight.

Spiral

A spiral stairway must be at least 26 inches wide at and below the handrail. Each tread must have a clear depth of at least 6 3/4 inches measured 12 inches from the narrow edge, and risers can be as tall as 9 1/2 inches. Headroom must be at least 78 inches. Spiral stairs are limited to serving a floor area of no more than 400 square feet.

Winders

Winder treads, the pie-shaped treads that turn a corner without a landing, must be at least 10 inches deep at the walk line, measured 12 inches from the narrow side. At the narrowest point within the clear stair width, they can be no less than 6 inches deep.¹¹ The 3/8-inch uniformity tolerance still applies to those walk-line depths.

Structural Loads

Stair framing must carry a minimum uniform live load of 40 pounds per square foot. Each tread must independently support a 300-pound concentrated load applied to a 2-inch by 2-inch area, and the design must use whichever load produces greater stress.¹² Handrails and guards must resist a 200-pound concentrated load applied in any direction, and guards must also handle 50 pounds per linear foot applied uniformly. Undersized stringers, fasteners, or baluster connections can fail a structural inspection even when every visible dimension is right.

Fire Protection Under Stairs

Enclosed space under a stairway that’s accessible through a door or access panel must be finished on the enclosed side with 1/2-inch gypsum board on the walls, on the underside of the stair, and on any soffits. Under-stair storage tends to accumulate combustibles, and an unprotected stair structure can burn through and cut off the primary escape route from upper floors. It’s one of the most overlooked requirements in residential work, because the space usually looks finished from the room side once drywall goes up.

Lighting and Switches

Interior stairways need an artificial light source that illuminates treads and landings to at least 1 foot-candle, measured at the center of the treads and landings. When a stairway has six or more risers, a wall switch must be installed at each floor level so the light can be turned on before stepping onto the stairs from either direction.¹³ Shorter stairs can get by with one switch. Remote, central, and automatic controls are accepted in place of standard wall switches. Exterior stairways are covered by a separate lighting provision, not R303.7.

Permits, Inspections, and Existing Stairs

State law directs municipalities and counties to enforce the code through permitting and inspection, and allows them to contract with other jurisdictions or consultants to do so.¹⁴ Building a new stair or doing a major stair renovation almost always requires a permit from the local building department. Work done without a permit, or work that doesn’t pass inspection, can bring stop-work orders, mandatory tear-out, or problems at resale.

Existing stairs that met code when they were built are generally grandfathered and don’t have to be brought up to the current standard. Substantial renovation of those stairs is the point at which current requirements typically apply.

1
South Carolina Department of Labor, Licensing and Regulation. Building Code Adoption
2
ICC Digital Codes. South Carolina Residential Code R311.7.5.1 Risers
3
Legal Information Institute. South Carolina Code of Regulations 8-1210 IRC R311.7.5.1 Risers
4
International Code Council. 2021 International Residential Code IRC R311.7.2 Headroom
5
International Code Council. 2021 International Residential Code IRC R311.7.8 Handrails
6
International Code Council. 2018 International Residential Code IRC R311.7.8.4 Continuity
7
International Code Council. 2018 International Residential Code IRC R312.1.2 Height
8
International Code Council. 2021 International Residential Code IRC R312.1.3 Opening Limitations
9
International Code Council. South Carolina Residential Code 2018 R311.7.6 Landings for Stairways
10
International Code Council. 2021 International Residential Code IRC R311.7.3 Vertical Rise
11
International Code Council. 2021 International Residential Code IRC R311.7.5.2.1 Winder Treads
12
International Code Council. 2024 International Residential Code IRC R301.5 Live Load
13
International Code Council. 2018 International Residential Code IRC R303.7 Interior Stairway Illumination
14
South Carolina Legislature. South Carolina Code of Laws Title 6 Chapter 9 Building Codes