Escaliers: Termes, Localisation et Calculs de Base

• Study notes on staircases including terminology, localization, and basic calculations.

Terms and Localization

• Terms:
  • Épaisseur du plafond: Ceiling thickness.
  • Chevêtres: Header joists.
  • Longueur du puits: Well length (stairwell).
  • Giron: Tread depth.
  • Contremarche: Riser.
  • Profondeur de marche: Tread depth.
  • Échappée: Headroom.
  • Marche: Tread.
  • Nez: Nosing.
  • Butoir: Stair base stop.
  • Course: Run.
  • Limon: Stringer.
  • Elévation: Rise.

Basic Terms

• Escalier: Series of steps of equal height used to ascend or descend.
• Puits: Opening arranged between the joists of an upper floor, allowing the passage of the staircase and its users.
• Elévation: Height between two finished floors.
• Limons: Piece of wood or metal supporting the treads and risers.
• Giron (G): Horizontal part of the stringer on which the tread rests.
• Marche: Pieces of wood or metal, placed horizontally on the giron, the tread of the stair.
• Contremarche (CM): Vertical part of the riser. Piece closing the opening between 2 treads.
• Course: Horizontal distance between the faces of the first and last risers.
• Nez de marche: Edge of the tread extending beyond the risers by 1 inch.
• Épaisseur du plafond: Total thickness of the ceiling including finishes.
• Échappée: Vertical clear height between the finished underside of the ceiling to the end of the well, and the imaginary line passing through the edge of the treads.
• Profondeur de marche: Total tread depth = giron + nez.
• Chevêtres: Pieces of wood that are part of the floor structure, placed at the ends of the stairwell on which the stringers rest.
• Butoir: Piece of wood fixed to the floor at the bottom of the staircase against which the stringers abut.
• Volée: Series of steps between two floors or landings, a flight of stairs.
• Ligne de foulée: Imaginary line representing approximately where the feet are placed when going up or down the stairs.
• Main courante: Handrail, pieces placed at an angle following the angulation of the staircase on which the hand is placed, the handrail angle matches the stair angle.
• Garde-corps: Guardrail, pieces placed horizontally supported by bars or balusters preventing a fall.
• Barreaux ou barrotin: Balusters, pieces placed vertically supporting the handrail or guardrail. When these measure 1 inch by 1 inch, they must be placed 5 inches center/center.

Important Notes

• According to the CNB, the minimum and maximum heights of the risers for a PRIVATE staircase are:
  • (125 MM and 200 MM) or (5 15/16 "and 7 7/8").
• According to the CNB, the minimum and maximum heights of the risers for a PUBLIC staircase are:
  • (125 MM and 180 MM) or (5 15/16 "and 7 1/16").
• The IDEAL riser height is: 170 MM or 6 11/16".
• According to the CNB, the minimum and maximum depths of the treads for a PRIVATE staircase are:
  • (210 MM and 355 MM) or (8 4/16 "and 14").
• According to the CNB, the minimum and maximum depths of the treads for a PUBLIC staircase are:
  • (280 MM and NO LIMIT) OR (11 "AND NO LIMIT).
• The MINIMUM headroom above stairs, ramps and landings is: 1950 MM or 76 12/16".
• The MINIMUM AND MAXIMUM handrail height is: (865 MM and 965MM) or (34 "and 38").
• When the top of a balcony is located more than 60 CM (2 feet) from the finished ground, the guardrail must have a minimum height of 90 CM (36 inches). When the top of a balcony is located more than 180 CM (6 feet) from the finished ground, a guardrail of at least 107 CM (42 inches) is required.

Basic Calculation for Stair Design

• Rise = Riser.

Formula in Imperial Measurement

• Rise DIVIDED BY 7.25 Inches = NUMBER OF RISERS.
  • Example: 101 inches DIVIDED by 7.25 inches; 13.93 CM round up to 14 CM.

Formula in Metric Measurement

• Rise DIVIDED BY 185 MM = NUMBER OF RISERS
  • Example: 2565 mm DIVIDED by 185 mm = 13.86 cm round up to 14 CM.

Run = Tread

• Formula in Imperial Measurement: When we have an unlimited run, we start with the number 9.25 inches.
• Formula in Metric Measurement: When we have an unlimited run, we start with the number 235 mm.
• When we have a LIMITED run, we divide the run by the number of treads.
• Note: TO FIND THE NUMBER OF TREADS YOU MUST TAKE THE NUMBER OF RISERS MINUS 1: Example 13 CM = 12 treads.
• Example: 122 inches DIVIDED BY 12 TREADS: 10.166 OR 10 3/16". 3099 mm DIVIDED BY 12 TREADS: 258 mm.

Stair Calculation Example

Given

• Rise: 109 INCHES (9 FEET 1 INCHES).
• Run: 140 INCHES (11 FEET 8 INCHES).
• Tread thickness: 1.125 or 1 1/8.

To find the number of risers

• Rise divided by (7 ½ or 185 mm).
• 109 divided by 7.25 = 15.03 risers rounded to 15.

To know the height of the risers

• Rise divided by the number of risers chosen.
• 109 divided by 15 = 7.266 or 7 and 1/4 inches.

To know the height of the first riser

• Riser height - tread thickness + floor finish of the lower floor.
• 7.266 - 1.125 = 6.141 or 6 and 1/8 inches.

To know the height of the last riser

• Riser height + tread thickness - floor finish of the upper floor.
• 7.266 + 1.125 = 8.391 or 8 and 3/8 inches.

To find the Number of Treads

• Number of risers - 1 =.
• 15 risers - 1 = 14 treads.
• Run divided by the number of treads.
• 140 inches divided by 14 = 10 inches.
• Important: IF WE DO NOT HAVE A RUN, WE WILL TAKE AS A STARTING IDEAL VALUE 9⅛ OR 235 MM.

Recap

• Number of risers: 15.
• Riser height: 7 ¼.
• Height of the first riser: 6 and 1/8 inches.
• Height of the last riser: 8 and 3/8 inches.
• Tread length: 10 inches.
• Once the staircase has been calculated, it must be checked to see if it is comfortable to use, for this you need two elements, (THE TREAD RUN) AND THE HEIGHT OF THE RISER.
  • First calculation: 1 tread + 1 riser: 16⅝ to 18 1/8 is equal to 425mm to 460 mm.
  • Second calculation: 1 tread + 2 risers: 23 7/8 to 25 is equal to 605 mm to 635 mm.
  • Third calculation: 1 tread x 1 riser: 70 to 75 is equal to 45000mm to 48500 mm.
  • Stair step calculation plan NO 3133-V-1.
  • First Calculation: 10 + 7 ¼ = 17 ¼ OK.
  • Second Calculation: 10 + 7 ¼ + 7 ¼: 24 ½ OK.
  • Third Calculation: 10 X 7.25: 72.25 OK.
• IMPORTANT: IT MUST BE ENSURED TO OBTAIN AT LEAST 2 CALCULATIONS OUT OF 3.

Formula to Find the Length of a Stairwell

• (HEADROOM + CEILING THICKNESS) X TREAD / RISER + NOSING.
• Example: (take the supplied plan 3133-v1 sheet 3-6).

Information provided on the plan

• Headroom: 6 feet 8 inches = 80 inches.
• Ceiling thickness: 12 inches (fictitious).
• Tread: 10 inches.
• Risers: 7 ¼ or 7.25.
• Nosing: 1 inch.

Calculation

• 80 + 12 = 92 x 10 = 920 / 7.25 = 126.896 + 1 = 127.896 (128 inches).

Formula to find the headroom

• (WELL - NOSING) X RISERS / TREAD - CEILING THICKNESS.
• Example: (take the supplied plan 3133-V1 sheet 3-6).
  • 128 - 1 = 127 x 7.25 = 920.75 / 10 = 92.075 - 12 = 80 inches.

Formula to find the gross length of the Stringer

• RUN² + RISE² = v.
• Important: ALWAYS ADD APPROXIMATELY 12 INCHES AS A SAFETY MARGIN.

Method of Attaching Stringers to Header Joists

• Should be at minimum 3 ½ Inches.