Colorado State Building Codes for Stairs

By Kimberly Wylie

When constructing a new building, whether commercial or residential, state and federal regulations give details on how buildings are to be designed and constructed. These building codes ensure the safety of the occupants that utilize the buildings. Stairways are one area that building codes focus on because of the potential hazard they create. In Colorado, there are several building codes that dictate the design and construction of stairs.

Make your staircase Colorado ready.

No More or Less

Colorado dictates the range of measurements associated with stairways. They must be at least 36 inches wide. The treads must have a run of at least 10 inches and cannot have a rise greater than 7 3/4 inches. Treads also may not have a slope greater than a 2 percent grade. The run and the rise of the staircase also has to be fairly consistent over the course of the stairway, with less than a 3/8-inch deviance on either dimension. Open risers are permitted in staircases; however, that opening must be less than 4 inches. A nosing must be provided on treads less than 11 inches in width and must be at least 3/4-inch in width but not more than 1 1/4-inch. The head room from stair tread to ceiling must be 6-feet-8-inches or greater. A single flight of stairs should not have a rise of more than 12 feet, between the floor levels and/or platforms. Staircases also must be illuminated properly.

Railing Codes

Railings are required on stairways to prevent falls and provide support. Colorado has adopted the International Code Council's guidelines for these regulations. Railings along the stairs shall not extend beyond the stairway, more than 4 1/2 inches on either side. Handrails cannot be less than 31 1/2 inches from the stair tread, if there is only a handrail installed along one side of the stair, or 27 inches in height if there are handrails installed along both sides of the stairs. Spacing between balusters should not exceed 4 3/8 inches. When a base rail is used, the opening between the bottom of the base rail and the stair tread must be small enough that a 6-inch sphere could not pass through. Railings are required on open sides of staircases. If both sides of the stairway are enclosed, a handrail is required on at least one side.

Guardrail Codes for Landings

Guardrails are required in Colorado on landings and any level walking areas that are 30 inches or more above the floor or grade below. The handrail on the railing must be at least 36 inches high. In addition, the spacing between the balusters must be less than 4 inches. All railings--guardrails and stair rails--must be built to withstand at least 200 lbs. of pressure on the handrail.