Measurements for the Rise & Tread of Wooden Steps

Code Requirements

• Always check local building codes before planning a stairway or steps, indoors or out. Many codes will specify width of treads and height of risers, based on the length of the stairs and the total vertical rise. The total rise will affect both tread and riser dimensions. Steep steps generally have taller risers and narrower treads; gradual inclines use shorter risers and wider treads.

Sizes the Same

• Stair risers and treads must be the same for the length of the stairway; varying heights can be a hazard, because people, especially older ones, tend to expect to step the same every time. Risers that are open or only partly covered can also be a hazard, especially if the opening is more than 4 inches. Tread boards must be at least 1-inch thick and 1 1/2 inches for open risers.

Preferred Height and Width

• A National Institutes of Health publication says an experiment with stairs found the optimum riser height to be 7.2 inches, the optimum tread to be 11 or 12 inches. Risers of 4 inches were unacceptable to almost all study participants; so were heights over 9 inches. Many building codes set riser heights at 7 3/4 to 8 1/2 inches and treads at 8 1/4 to 9 inches, but allow slight variations to accommodate different situations.

Landings

• Stairs that must change directions present special problems. A frequent solution is to use an L-shaped stairway with a landing at the point where directions change. Any stairway that rises 12 feet or more requires at least one landing. Landing widths can vary but should be at least as long as the width of the tread. Landings at the top of a stairway must be wide enough to allow clearance for a door to open.

'Winders'

• Curved or winding stairways present more problems because one side of the treads must be smaller, which creates a hazard. Many building codes specify minimum widths for the small tread end. These vary. Some require that the width of the tread 18 inches from the narrow end be at least the width of the full tread; others specify a minimum of 6 inches of tread at the narrow end. Many stairs need safety handrails, but they are always essential with "winders."