What is a winder staircase?

A winder staircase uses tapered (pie-shaped) treads instead of a flat landing to turn a corner. A quarter-turn winder uses 3 winder treads to turn 90°, while a half-turn uses 6 winders for 180°. Winders save space compared to landings but must comply with specific Part K rules for the going measurement and minimum tread width.

Where is the going measured on a winder tread?

Under Building Regulations Part K, the going on winder treads is measured on the walking line, which is 270mm from the narrow (inner) edge. The going at this point must be between 220mm and 300mm for domestic stairs. All winder treads in a set should have equal going at the 270mm measurement line.

What is the minimum width at the narrow end of a winder?

Part K requires a minimum tread width of 50mm at the narrow (inner) end of each winder tread. This prevents the tread from tapering to a dangerous point. In practice, most carpenters aim for 75mm or more at the narrow end for safer footing. The narrow end meets the newel post at the turn.

How many winder treads do I need for a quarter turn?

A standard quarter turn (90°) uses 3 winder treads, each turning 30°. This is the most common arrangement. You can use 2 winders (45° each) or 4 winders (22.5° each), but 3 is the standard. The winders replace what would otherwise be a quarter landing, saving approximately 800-900mm of floor space.

Can winder stairs comply with Building Regulations?

Yes, winder stairs are fully compliant with Part K when designed correctly. The key requirements are: going measured at 270mm from narrow end must be 220-300mm, narrow end minimum 50mm, rise 150-220mm, and the 2R+G formula must give 550-700mm. A headroom of 2000mm must be maintained. Building control will check these dimensions.

TradeCalculator

Winder Staircase Calculator

Calculate winder tread geometry, going measured at 270mm from narrow end, minimum 50mm narrow end, and Part K compliance.

Winder Type

Quarter (90°) or half (180°) turn

Total Rise (floor to floor)

Finished floor to finished floor

Target Rise Per Step

150-220mm (Part K)

Straight Tread Going

Going on straight treads

Stair Width

Clear width between strings

Price Per Tread (optional)

How We Calculate This

This calculator determines winder tread geometry for quarter and half-turn staircases. It checks compliance with Part K for going at the 270mm walking line and the minimum 50mm narrow end requirement.

The formula

Winders: 3 for quarter turn (90°), 6 for half turn (180°)
Going measured at 270mm from narrow end
Narrow end: minimum 50mm
2R + G must be 550-700mm

Part K compliance

Rise: 150-220mm per step
Going at 270mm line: 220-300mm
Narrow end: minimum 50mm
Pitch: maximum 42° for domestic

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.