403A Stair Construction 2 — Questions and Answers
Question 1: What characterizes a 'housed stringer' (closed stringer) in stair construction?
- Notches are cut along the top edge to receive treads and risers
- Treads and risers fit into routed grooves on the inside face of the stringer (Correct answer)
- The stringer is concealed entirely within a finished wall
- The stringer is fabricated from engineered lumber
Correct answer: Treads and risers fit into routed grooves on the inside face of the stringer
A housed stringer has dadoes (routed grooves) machined into its inner face so the treads and risers slot in, creating a clean finished appearance on both sides.
Question 2: What is the maximum allowable variation in riser height within a single flight of stairs according to the NBC?
- 3mm
- 5mm (Correct answer)
- 8mm
- 10mm
Correct answer: 5mm
The NBC limits the variation between the tallest and shortest riser in any one flight to 5mm to prevent tripping hazards.
Question 3: What is the maximum permitted opening between balusters on a stair guard?
- 75mm
- 100mm (Correct answer)
- 125mm
- 150mm
Correct answer: 100mm
The NBC requires that no opening in a guard allow passage of a 100mm sphere, preventing a child's head from becoming trapped.
Question 4: Under the NBC, a guard must be provided when the stair or surface is adjacent to a drop of more than:
- 450mm
- 600mm (Correct answer)
- 750mm
- 900mm
Correct answer: 600mm
The NBC requires guards wherever a walking surface or stair is adjacent to a difference in elevation exceeding 600mm.
Question 5: What is the minimum clear width required for a residential staircase under the NBC?
- 760mm
- 860mm (Correct answer)
- 900mm
- 1000mm
Correct answer: 860mm
The NBC requires a minimum clear stair width of 860mm for residential stairs to allow safe passage and furniture movement.
Question 6: A 'winder' tread is used in stair construction primarily to:
- Provide additional structural support to the stringer
- Allow the staircase to change direction without a full landing (Correct answer)
- Increase headroom at the bottom of the staircase
- Reduce the total number of risers required
Correct answer: Allow the staircase to change direction without a full landing
Winder treads are pie-shaped or tapered treads that allow a staircase to turn a corner without consuming the floor space needed for a full landing.
Question 7: What is the primary purpose of an intermediate landing in a long staircase?
- To increase the total rise of the staircase
- To provide a level rest platform and satisfy code limits on continuous flight length (Correct answer)
- To reduce the number of stringers required
- To meet minimum headroom clearance requirements
Correct answer: To provide a level rest platform and satisfy code limits on continuous flight length
Landings provide a safe level platform to rest on, allow changes in direction, and are required by code when a flight of stairs would otherwise be excessively long.
403A Stair Construction 2
What characterizes a 'housed stringer' (closed stringer) in stair construction?