Standard Layout for Stairs

Standard

• Standard-incline stairways are the most popular layout in homes but take up a lot of room. According to the International Residential Code, stairways must be at least 36 inches wide and have at least 80 inches of headroom, as measured from the handrail. At least one continuous handrail is required on one side of each flight. However, a handrail cannot project more than 4.5 inches into the stairway. The minimum clear width of the step below the handrail must be at least 31.5 inches if there's one handrail or 27 inches if there are two handrails.

Spiral

• Spiral staircases take up far less space than a standard stairway and can be bought pre-built from the factory. They must have a minimum clear width at and below the handrail of 25 inches. The top of each step must be at least 7.5 inches from the edge to the riser at its widest point. The rise between each step must be no more than 9.5 inches. The minimum headroom must be 78 inches. Spiral staircases must also have at least one continuous handrail.

Bulkhead Enclosure

• Standard or spiral stairways that allow access to a basement must follow the same standards as those in above-ground spaces. However, one stair type that doesn't have to meet these standards is the bulkhead enclosure stairway. This type of stairway connects an outside grade level such as a backyard or driveway to a lower level, such as a basement. It cannot be the only way to enter or exit a basement, it must be less than 8 feet long, and it must have at least one hinged doorway covering the bulkhead entrance that swings outward.

Lighting

• Stairways of all types require artificial lights. At minimum, the light source must be near each landing. For exterior stairways, the light source needs to be near the top of the landing. If the stairway provides access to a basement from outside, a light at the bottom landing is required. If an artificial light is directly above a stairway section and can light each tread and landing according to minimum standards, then the top and bottom landing do not need separate lights.