Though sometimes constructed of brick, concrete or metal, stairs in the home are usually constructed of wood. The typical components of wood stairs are the stringer, tread and riser. The stringer is the long, diagonal supports that run the entire length of the stairs. The supports are blocked, cut or notched to accept the individual treads and risers. There are usually two stringers, one on each side and occasionally a third in the middle. The tread is the flat surface that is stepped on; the width of the tread is equivalent to the run. The riser is the vertical component; the height of the riser is equivalent to the rise. Stairs without risers are called “open” stairs.
For safety and accessibility reasons, stairs are required to be constructed according the following general guidelines:
- The maximum height of the riser (or rise that a person needs to step up to the next stair) is 8 to 8-1/4 inches.
- The riser’s height should not vary more than 1/2 inch between the shortest and tallest risers.
- ‘The minimum width of the tread (or run) on which a person places their foot is 8 1/4 to 9 inches.
- Tread should be level with a maximum deviation of a 2% slope.
- To ensure stability, the minimum width at any point of stringer should be 3-1/2 inches.
- A vertical clearance of 6 feet 8 inches needs to be maintained between the stair and ceiling at all points.
- The stairwell must be a minimum of 36 inches wide.
Landings are designed to provide a safe standing area on each side of a door and allow easy opening and closing of the door. A landing area is required on both sides of all exterior/exit doors of the home. In addition, interior doors that open towards a stairwell (at the top) require a landing at the top of the stairs to provide a safe standing area when the door is opened. The minimum size of the landing is a 3-foot by 3-foot area.
Exterior landings should provide a minimum step up to the threshold of 1-1/4 inches to 6 inches in order to prevent water penetration from rain or snow.
For safety reasons, the maximum step down distance for all landings (from the top of the threshold to the landing) is 8-1/4 inches.
Handrails and guardrails are sturdy handholds and barriers that follow the outside, and sometimes inside, perimeter of the stairs and landings. The rails are designed to prevent falls and to provide a handhold, especially when walking up or down the stairs.
For safety reasons, handrails are required on all stairs with a total riser height greater than 24 inches (2 or 3 steps) and guardrails are required on open stoops and landings that are more than 24 inches above the floor or grade. (Handrails on an open stairwell also act as guardrails.) To function as an adequate barrier to prevent falls, stairs are required to have a minimum height of 34 inches, and guardrails on all porches, balconies, or raised floor surfaces are required to have a minimum height of 36 inches .
In addition, to prevent injury to children, balusters or spindles should:
- be vertical so as not to create a climbing grid, and
- have a space or gap no greater than 4 inches to prevent children from squeezing through or getting stuck in the opening.