Stairs can be dangerous. People fall on stairs every day and the consequences can be serious. Senior citizens are especially at risk and the effects for them can be long lasting. Children under the age of 5 are also prone to falls on stairs. While there are a variety of ways to minimize the risk of falling, one of the key elements you should consider is using safe stair step dimensions.
Regulations
Guidelines in the United States on stair design are established by a variety of governmental organizations. These requirements may vary depending on the state and city in which you live and whether the stairs are for a home or commercial building. The Americans with Disabilities Act offers guidelines as does the U.S. Department of Labor, Occupational Safety and Health Administration. You should also consult your state and city building codes.
Riser
The riser is the vertical element in a stairway. Riser height must be the same within each flight of stairs, including the foundation to the first tread. The variation in riser height cannot be over 1/4 inch in any stairway system, according to OSHA. The maximum and minimum height may vary based on local building codes. In New York State, for example, the minimum height is 4 inches and the maximum height is 8 1/4 inches. According to OSHA, the overall slope of a stairway should be between 30 to 50 degrees.
Open risers are not permitted under the ADA guidelines. However some local building codes allow them and some allow them provided the opening will not pass a 4-inch sphere. This is for child safety reasons.
Tread
Tread is defined as the horizontal element in a stairway. As with the riser, tread depth must be the same within each flight of stairs. The allowable difference in tread depth cannot be over 1/4 inch in any stairway system, according to OSHA. ADA regulations state the tread cannot be less than 11 inches deep measured from riser to riser. The tread should be not be slippery and should allow for drainage; however the pitch of the tread should not exceed 2 degrees. The tread should have a solid surface.
Nosing
The nosing or leading edge of the tread should not project more than 1 1/2 inches beyond the riser, according to the ADA. Additionally, the underside of the nosing should not be abrupt. The radius of the curvature cannot be greater than 1/2 inch. Alternatively the riser can be sloped so that the underside of the nosing can have an angle of not less than 60 degrees from the horizontal.
For additional safety, do not use visually distracting patterns on the treads. You can paint the nosing a different color, but do not use tape as it may become a tripping hazard.
