Spiral stairs save space, but the design decisions — diameter, tread geometry, centre column stiffness, guard layout, and code compliance — all need to happen before a price can be attached. A spiral that fits the space on a sketch may not work under the BC Building Code.
How much does a custom spiral stair cost in Vancouver?
A custom steel spiral stair in Metro Vancouver typically ranges from $8,000 for a basic exterior deck-access spiral to $25,000–$40,000+ for a feature interior spiral with custom treads, a finished centre column, and a glass or cable guard. Diameter, tread material, finish, and whether the stair is a primary egress or secondary access are the main cost drivers. Every spiral is quoted after a site review.
Diameter and tread geometry
Spiral stair diameter is set by two constraints: the space available and the walkable tread width required by code. A tighter diameter gives a narrower walkline and less comfortable walking depth at the outer edge of the tread. Most residential spirals in Metro Vancouver use a 1500–2000 mm (60"–78") diameter. The centre column must be stiff enough to resist the helical torsion loading — this is not a post, it is a structural tube.
- 1500 mm (5 ft) diameter: compact, secondary access only in most code interpretations.
- 1800 mm (6 ft) diameter: more comfortable, can work as a primary stair if walkline meets code.
- 2000+ mm (6.5 ft+): generous, feature stair range.
BC Building Code: can a spiral be a main stair?
The BC Building Code limits the use of spiral stairs as required means of egress. Under most Part 9 residential provisions, a spiral stair can serve as a secondary stair but is restricted as the sole required egress from a floor level. The tread walkline, the minimum walkable width, and the tread run at the walkline all have code minimums. Confirm the applicable provisions and the spiral's walkline dimensions with your AHJ before committing to a spiral as the only stair.
Guard and handrail on a spiral
The outer guard wraps the spiral. On most designs the outer balustrade is a structural component, not just a guard — it ties back to the centre column and the landing at each level. Glass infill, cable, or steel rod are common. The inner handrail wraps the centre column. Confirm guard height and sphere-passage requirements with your AHJ.
Related questions
Can a spiral staircase be a main stair?
In most residential BC Building Code interpretations, a spiral stair can serve as a secondary stair but is restricted as the sole required egress from a floor. Walkline dimensions, tread depth at the walkline, and riser consistency all need to comply with applicable code provisions. Confirm with your AHJ before treating a spiral as the primary egress.
How much space does a spiral stair need?
A 1500 mm (5 ft) diameter spiral needs roughly a 1700 mm (5.5 ft) square opening when you include the centre column and the outer guard. A 1800 mm (6 ft) diameter stair needs about a 2000 mm (6.5 ft) square opening. Allow for headroom through all floor levels — the helical geometry means some part of the upper stair is always directly above the lower stair.
What is the centre column made from?
Most custom steel spiral stairs use an HSS round or square structural tube as the centre column. The column carries the helical torsion loading from the treads and the guard — it is not decorative. Column diameter is sized by the engineer based on the stair height and the number of treads.
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