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Presentation 36:. STAIR RISE AND RUN. Unit Run. Unit Rise. Unit Run. Total Rise. Unit Rise. Unit Run. Total Run. Unit Rise. Rise and Run. Stairs have a rise and run. Similar to rafters, rise is vertical and run is horizontal. Rise and Run.
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Presentation 36: STAIR RISE AND RUN
Unit Run Unit Rise Unit Run Total Rise Unit Rise Unit Run Total Run Unit Rise Rise and Run • Stairs have a rise and run. • Similar to rafters, rise is vertical and run is horizontal.
Rise and Run • Unit rise and unit run do not include the tread nosing. Nosing Tread Unit Run Riser Unit Rise
Stair Design • Building stairs involves several options. Second Floor • In this design there are threetreads and four risers. First Floor
Stair Design • Another set might have four treads and five risers. • Deciding which to use depends on stair usage. Which is best?
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″
TotalRise Starting Information • Total rise must be measured. Second Floor • Assume for now there is ample room to land the stairs on the first floor. First Floor
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.
Number of Risers • Then the unit rise could be either 30″ ÷ 4 = 7 ½″ with 4 risers or 30″ ÷ 5 = 6″ with 5 risers
Determining Unit Run • Tread width may be found from the Rise/Run rule. • 17″ – 7 ½″ = between 9 ½″and 10 ½″ • 17 – 6 = between 11″and 12″ 9 ½″–10 ½″ 11″–12″ 6″ 7 ½″
Example • What are the possible unit rises and runs for a stair with a total rise of 102″?
Example • 102 ÷ 8 = 12.75 13 risers.
Example • Also 14 or possibly 15 risers.
Example • 102 ÷ 13 = 7.86 7 7/8″ unit rise.
Example • 17 – 7 7/8″ = between 9 1/8″ and 10 1/8″ unit run.
Example • 102 ÷ 14 = 7 5/16″ unit rise. • 17 – 7 5/16″ = 9 11/16″ and 10 11/16″ unit run.
Example • 102 ÷ 15 = 6 13/16″ unit rise. • 17 – 6 13/16″ = 10 3/16″ and 11 3/16″ unit run.
Design • Deciding which to use depends on the intended use and available total run. • 7 7/8″ steep • 7 5/16″ medium • 6 13/16″ gentle • Check local building codes for more guidance.
Conclusion • Stairs have a rise and run. • Unit rise = total rise ÷ # of risers. • Unit run may be found using Rise + Run = between 17″ 18″