Read This Before Building or Renovating Your Staircase

A staircase is an important part of any multi-storey building. Before building or renovating the stairs, there are certain regulations for stairways from both the International Residential Code (IRC) and The International Building Code (IBC). This code helps in building a safe staircase with the right step height, width, and depth. This article will walk you down through the important codes to be followed for your staircase.

Understanding Stair Riser and Stair Depth Building Codes

Stair Tread Depth

IBC defines tread depth as the horizontal distance between the vertical planes of the foremost projection of adjacent treads, seen from a 90-degree angle to the tread’s leading edge. It refers to the flat surface where a person places their foot. The Industrial Building Code (IBC) and the Occupational Safety and Health Administration (OSHA) have different specific stair depth codes.

According to OSHA, any standard stair (apart from alternating tread stairs, ship stairs, or spiral stairs) should have a minimum stair tread depth of 9.5 inches or 24 cm. On the other hand, according to IBC, stair tread depth must be at least 11 inches or 27.94 cm deep. Group R-2, R-3, and U being the exception, should have a minimum tread depth of 10 inches or 25.4 cm.

• OSHA Minimum Stair Tread Depth: 9.5″inch (240 mm)

• IBC Minimum Stair Tread Depth: 11″inch (279 mm)

• IBC Exceptions (Group R-2, R-3, and U): 10″inch (254 mm)

Stair Riser Height

OSHA has defined a stair riser as the upright (vertical) or inclined member of a stair that is located at the back of a stair tread or platform and connects close to the front edge of the next higher tread, platform, or landing. IBC has described riser height as the distance measured vertically between the nosings (the leading edge) of adjacent treads.

Similar to stair tread depth, stair riser height also varies according to OSHA and IBC, depending on the type of stairway. According to OSHA, standard stairs must have a maximum riser height of 9.5 inches or 24 cm. The minimum and maximum stair riser heights according to IBC must be 4 inches or 10.16 cm and 7 inches or 17.78 cm respectively. In exception groups of R-2, R-3, and U occupancies, the maximum riser height should be 7-3/4 inches or 19.7 cm according to IBC.

• OSHA Maximum Stair Riser Height: 9.5″inch (240 mm)

• IBC Minimum and Maximum Stair Riser Height: 4″inch (102 mm) – 7″inch (178 mm)

• IBC Exceptions (Group R-2, R-3, and U): 7-3/4″inch (197 mm)

Other Stair Code Requirements

Stair Width

• Minimum Width of Stairways Above the Permitted Handrail Height and Below the Required Headroom Height - 36 inches or 914 mm

• Minimum Width of Stairways at and Below the Handrail Height, Including Treads and Landings - 31.5 inches or 787 mm (where a handrail is installed on one side) 27 inches or 698 mm (where handrails are installed on both sides)

Headroom

• Minimum Headroom in Stairways Measured Vertically From the Floor Surface of the Landing - 6 feet 8 inches or 2032 mm

• Minimum Headroom in Stairways Where the Nosings of Treads at the Side of a Flight Extend Under the Edge of a Floor Opening Through Which the Stair Passes - 43/4 inches or 121 mm

Vertical Rise

• Maximum Vertical Rise Between Floor Levels or Landings - 151 inches (3835 mm)

Walkline

• Distance of Walkline From the Inside of Turn - 12 inches or 305 mm

The 12-inch dimension shall be measured from the widest point of the clear stair width at the walking surface.

Handrails

• Minimum and Maximum Height of Handrail - 34 inches or 864 mm and 38 inches or 965 mm

• Maximum Handrail Projection - 4.5 inches or 114 mm on either side of the stairway

• Minimum Space Between the Wall and the Handrails for Handrails Adjacent to a Wall - 1.5 inches (38 mm)

Staircase Landing Width

• Depth in the Direction of Travel - Minimum 36 inches