2024 Ontario Building Code Guide: Stair Tread, Winder, and Spiral Stair Requirements
Sarah's Expert Insight
OBC Compliance Specialist
"Staircase compliance is one of the most scrutinized aspects of residential inspections in London, Oakville, and Muskoka; even a 5mm variance can result in a failed inspection and costly delays. At empcontracting.ca Inc. your construction contractor in London, Ontario, we utilize precision framing and finishing techniques to ensure every winder and spiral staircase meets these rigorous 2024 OBC safety standards."
9.8.4.4. Tread Uniformity and Construction Tolerances
The Ontario Building Code (OBC) mandates strict precision for stair construction to ensure pedestrian safety. Rectangular treads must maintain a uniform run with a maximum tolerance of 5 mm between adjacent treads and a total of 10 mm between the deepest and shallowest treads within a single flight. Additionally, the slope of any tread must not exceed a ratio of 1 in 50.
Mixed Treads and Tapered Tread Measurement
When a flight consists of both tapered and rectangular treads within a dwelling unit, uniformity is measured 300 mm from the center line of the inside handrail. Specific allowances are made for tapered treads located at the bottom of a flight, which may exceed the run of the rectangular treads.
9.8.4.6. Winders and Spiral Staircase Regulations
Winders are a common feature in residential design but must adhere to specific geometry. They must converge to a center point and turn no more than 90 degrees per set. Individual winder treads must turn between 30 and 45 degrees, ensuring consistent footing. If multiple sets of winders are installed, they must be separated by at least 1,200 mm.
Spiral Stair Specifications
Spiral stairs require handrails on both sides, with the outer rail reaching at least 1,070 mm in height. Key requirements include:
- Clear Width: Minimum of 660 mm between handrails.
- Riser Height: Maximum of 240 mm.
- Tread Depth: Minimum 190 mm at a point 300 mm from the narrow edge.
- Headroom: Minimum clear height of 1,980 mm.
Note: Spiral stairs may only serve as the sole means of egress if the area serves no more than three people.
9.8.4.8. Tread Nosings and Safety Profiles
To enhance grip and visibility, tread nosings must have a rounded or beveled edge extending between 6 mm and 14 mm horizontally. If the stairs are finished with resilient material, the minimum extension requirement is reduced to 3 mm.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.