1. 1 Presentation 36: STAIR RISE AND RUN

2. 2 Rise and Run Stairs have a rise and run. Unit Rise Unit Run Total Run Unit Rise Unit Run Unit Rise Unit Run Total Rise Similar to rafters, rise is vertical and run is horizontal.

3. 3 Rise and Run Unit rise and unit run do not include the tread nosing. Riser Tread Nosing Unit Rise Unit Run

4. 4 Stair Design Building stairs involves several options. First Floor Second Floor In this design there are three treads and four risers.

5. 5 Stair Design Another set might have four treads and five risers. Which is best? Deciding which to use depends on stair usage.

6. 6 Rise/Run Rule A formula is used to keep the stairs at a safe and comfortable angle. Rise + Run = between 17″ and 18″ Run + two Rises = between 24 and 25 may also be used. The first one will be used for this demonstration. 7 ½″ rise and 10″ run are numbers that fit the formula. 7 ½″ + 10″ = 17 ½″

7. 7 Starting Information Total rise must be measured. First Floor Second Floor Total Rise Assume for now there is ample room to land the stairs on the first floor.

8. 8 Number of Risers Unit Rise = Total rise ÷ # of Risers # of Risers = Total Rise ÷ 8 (Rounded up) (8 is used as a starting point) e.g., If the total rise is 30″, then: # of risers = 30 ÷ 8 = 3.75 Rounding up gives 4 risers. Note that 5 risers may also work.

9. 9 Number of Risers Then the unit rise could be either 30″ ÷ 4 = 7 ½″ with 4 risers or 30″ ÷ 5 = 6″with 5 risers

10. 10 Determining Unit Run Tread width may be found from the Rise/Run rule. 7 ½″6″6″ 11″–12″ 9 ½″–10 ½″ 17″ – 7 ½″ = between 9 ½″ and 10 ½″ 17 – 6 = between 11″ and 12″

11. 11 Example What are the possible unit rises and runs for a stair with a total rise of 102″? # RisersUnit RiseUnit Run

12. 12 Example 102 ÷ 8 = 12.75  13 risers. # RisersUnit RiseUnit Run 13

13. Example Also 14 or possibly 15 risers. # RisersUnit RiseUnit Run 13 14 15

14. 14 Example 102 ÷ 13 = 7.86  7 7 / 8 ″ unit rise. # RisersUnit RiseUnit Run 137 7 / 8 ″ 14 15

15. Example 17 – 7 7 / 8 ″ = between 9 1 / 8 ″ and 10 1 / 8 ″ unit run. # RisersUnit RiseUnit Run 137 7 / 8 ″9 1 / 8 ″ & 10 1 / 8 ″ 14 15

16. 16 Example 102 ÷ 14 = 7 5 / 16 ″ unit rise. 17 – 7 5 / 16 ″ = 9 11 / 16 ″ and 10 11 / 16 ″ unit run. # RisersUnit RiseUnit Run 137 7 / 8 ″9 1 / 8 ″ & 10 1 / 8 ″ 147 5 / 16 ″9 11 / 16 ″ & 10 11 / 16 ″ 15

17. 17 Example 102 ÷ 15 = 6 13 / 16 ″ unit rise. 17 – 6 13 / 16 ″ = 10 3 / 16 ″ and 11 3 / 16 ″ unit run. # RisersUnit RiseUnit Run 137 7 / 8 ″9 1 / 8 ″ & 10 1 / 8 ″ 147 5 / 16 ″9 11 / 16 ″ & 10 11 / 16 ″ 156 13 / 16 ″10 3 / 16 ″ & 11 3 / 16 ″

18. 18 Design Deciding which to use depends on the intended use and available total run. –7 7 / 8 ″ steep Check local building codes for more guidance. –7 5 / 16 ″ medium –6 13 / 16 ″ gentle

19. 19 Conclusion Stairs have a rise and run. Unit rise = total rise ÷ # of risers. Unit run may be found using Rise + Run = between 17″  18″