What Is the Standard Run for Deck Stairs?

Unit Run

• Horizontal unit runs are the length of each stair, from front to back, that sit parallel to the ground. They should be no less than 10 inches, according to recommendations from the Council of American Building Officials as well as the 2000 International Code Council. The key to using a standard 10 inches for the horizontal stair run distance is to select a riser that will produce a comfortable stepping angle within local code regulations. A basic configuration is to use a 10-inch run with a stair riser measuring between 7 and 7.5 inches between each stair.

Unit Riser

• The stair riser is the vertical element found in a set of stairs, measured from the bottom to the top. It runs perpendicular to the ground. The CABO and the Code Council recommend that unit risers be no more than 7.5 inches. In fact, the United Brotherhood of Carpenters reports that stair risers range between 4 and 7 inches, so be sure to check what local codes are required in your area.

Outdoor vs. Indoor

• Most deck stairs are outdoors. Standard measurements still apply; unit runs should be no less than 10 inches and risers should be no more than 7.5 inches high. Many people, however, build longer, shorter stairs, such as stairs with a 12-inch run and 6-inch rise. It really just depends on your preference, deck size and stair location, as well as the elevation change from the ground to the deck floor. Short decks might only need one or two stairs, while tall decks require more stairs. You might consider narrower and taller stairs for taller decks so you use less material and have less stairs, thought if you live with children or elderly people, it might be worth the extra materials to build longer, shorter stairs for safety reasons.

Riser and Run

• Figuring out the right riser and run measurements can get confusing. Local building codes are a good start to the right measurements. One way to figure it out is by dividing the distance from the top of the deck to the bottom. For example, if the distance measures 37 inches, a riser height of seven and three-eighths should be used because it divides evenly five times into 37 inches (or close enough). So when 37 is divided by 5, the result is 7.4, which indicates this project needs 5 steps, each seven and three-eighths inches tall.

Other Considerations

• You should keep safety considerations to keep in mind when planning a deck stair project or other stair project. The CABO 1996 model code states that "open risers," which are stairs consisting of only treads, are no longer permitted because of safety concerns for young children and the elderly. It should also be noted that nosing projections are also considered hazardous to the elderly. The standard width of stairs is 3.5 feet. Stairs wider than 44 inches require handrails on both sides. Landings are commonly required by most fire codes for stairs rising higher than 12 feet.