- Draw your complete stairway on paper! It’s a lot easier to erase pencil lines than to tear out wood.
- The sum of all unit runs (tread less nosing) = TOTAL RUN
- The sum of all unit risers = TOTAL RISE (measured from FINISHED floor to FINISHED floor).
- As the angle of a stairway changes, so does the riser-tread ratio.
- Three general rules for Riser-Tread Ratio (excluding Tread nosing, which extends 1in. to 1 ½ in. beyond riser):
a. Rise plus tread width = 17 in. to 18 in.
b. Rise times tread width = 72 in. to 76 in.
c. Sum of two risers plus tread width = 24 in. to 25 in. - An “ideal” ratio is 7 in. rise and 10 in. tread. These dimensions may vary slightly if the rise and/or run of a stairway must be held within certain limits.
- Avoid going more than 8¼ in. rise or less than 9″ wide tread. Try to keep around the 34° to 37° angle.
- A main stairway should be at least 36 in. wide, or even 42 in. if possible, with 6 ft. 8 in. headroom. This width and height is needed for moving furniture as well as people.
- Handrails should be 30 in. to 34 in. above nosing of steps, and 34 in. high on landings.
- If you must turn a stairway 90°, using a landing is more desirable and safer than three winding steps (called winders). A landing is treated as a regular step with a larger tread. The landing can be supported by legs going down to the floor below, and it should be at least as wide and long as the width of the stairs. If you are making a “U” turn in the stairs, the landing will have to be at least two times the width of the stairs in order to accommodate the second set of stringers that lead on down. These stringers are tied into the framework of the landing in the same manner as though you were coming from the regular floor. Maintain the same rise and tread width all the way down.
- Using three winders, each tread tapers from a wide to narrow, but not pointed, tread at inside of turn. At a point 15″ to 18″ from the narrow end, where you normally walk, tread width on the three winders should be the same as the rest of the stairs. To determine proper size and shape of the three winders, first layout three full size winders on template of paper or cardboard and fit them into your turn.
Please check with your municipality to make sure your design complies with all building codes.