403A Stair Construction 1 — Questions and Answers
Question 1: What is the maximum unit rise permitted for interior stairs under the National Building Code of Canada?
- 180mm
- 200mm (Correct answer)
- 220mm
- 250mm
Correct answer: 200mm
The NBC limits interior stair risers to a maximum of 200mm to ensure safe and comfortable climbing.
Question 2: A staircase has a total rise of 2,800mm and requires 14 risers. What is the unit rise?
- 185mm
- 190mm
- 200mm (Correct answer)
- 210mm
Correct answer: 200mm
Unit rise = total rise ÷ number of risers = 2,800 ÷ 14 = 200mm.
Question 3: Which stair component directly supports the treads and risers along the sides of the staircase?
- Newel post
- Stringer (Correct answer)
- Baluster
- Nosing
Correct answer: Stringer
The stringer (also called a carriage) is the structural inclined board that supports the treads and risers.
Question 4: What is the minimum unit run (tread depth) required for residential stairs under the NBC?
- 210mm
- 220mm
- 235mm (Correct answer)
- 250mm
Correct answer: 235mm
The NBC requires a minimum tread depth (unit run) of 235mm for residential stairs to ensure safe foot placement.
Question 5: What is the minimum required headroom clearance for a staircase under the National Building Code of Canada?
- 1800mm
- 1900mm
- 1950mm (Correct answer)
- 2100mm
Correct answer: 1950mm
The NBC mandates a minimum of 1950mm of headroom measured vertically from the nosing line to the ceiling above.
Question 6: Using the stair comfort formula 2 × Rise + Run = 635mm, what tread depth is required for a unit rise of 190mm?
- 225mm
- 235mm
- 255mm (Correct answer)
- 275mm
Correct answer: 255mm
2 × 190 + Run = 635mm; 380 + Run = 635; Run = 255mm.
Question 7: What is the 'nosing' of a stair tread?
- The vertical face of the riser
- The horizontal projection of the tread beyond the riser below (Correct answer)
- The bottom rail of the handrail system
- The angled cut at the base of the stringer
Correct answer: The horizontal projection of the tread beyond the riser below
The nosing is the portion of the tread that overhangs or projects beyond the face of the riser below it.
403A Stair Construction 1
What is the maximum unit rise permitted for interior stairs under the National Building Code of Canada?