Stairs, Interior & Exterior Finishing
Stair construction, interior trim, drywall, door installation, exterior finishing, and building envelope systems.
- Calculate stair rise, run, and stringer layout per NBC requirements
- Identify stair components including stringers, treads, risers, and handrails
- Describe interior finishing techniques including drywall, trim, and door installation
- Explain the building envelope including vapour barriers, flashing, and siding
Lección 1
Stair Layout & Construction
Stair Geometry
Stair building requires precise mathematics. Every stair must provide safe, comfortable passage between floors while meeting strict code requirements. The relationship between rise (vertical height of each step) and run (horizontal depth of each step) determines the stair's comfort and safety.
Rise and Run
The typical rise and run for residential stairs is approximately 7-3/4 inch rise, 10 inch run. This is the standard combination tested on the exam - not 12 inch rise with 8 inch run, 6 inch with 6 inch, or 10 inch rise with 12 inch run. The NBC sets specific limits:
- Maximum riser height: 7-3/4 inches (approximately 200 mm) - not 6, 9, or 12 inches
- Minimum tread run: 255 mm (approximately 10 inches) - the NBC 2020 increased this from the legacy 210 mm to reduce stair fall injuries
- Consistency: The variation between any two risers cannot exceed 3/8 inch
Riser Consistency
The maximum allowed variation between the tallest and shortest riser in the same stairway is 3/8 inch. Inconsistent risers are a tripping hazard and a common code violation.
The Stringer
The purpose of a stringer in stair construction is the diagonal support that holds treads and risers. A stringer is not the handrail, the landing, or a railing post - it is specifically the diagonal structural member. Stringers are the backbone of the stair - they carry all the loads from the treads to the floor structure.
Types of stringers:
Cut (Sawtooth) Stringer
Construction: Notched to form steps
Material: Typically 2x12
Treads: Sit on top of the notches
Most common for residential stairs
Housed (Closed) Stringer
Construction: Routed grooves for treads and risers
Material: Typically 2x12 or wider
Treads: Slide into grooves
Used for: Finish stairs, higher quality
Calculating Stairs
The typical residential stair has a 7-3/4 inch rise and 10 inch run. The stringer is the diagonal support that holds treads and risers. All risers must be consistent within 3/8 inch.