Half-turn stair calculator for U-shaped layouts
A half-turn stair folds the climb into two parallel flights connected by a landing. It can reduce the required room length, but flight spacing, landing size, opening, and headroom all need to work together.
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Best for
- • Compact rectangular stair halls
- • Layouts needing two parallel flights
- • Comparing footprint against a straight stair
Measurements to take
- • Finished floor-to-floor height
- • Lower and upper flight lengths
- • Flight width and gap
- • Turn direction
- • Opening length and floor thickness
Results you get
- • Step distribution across both flights
- • Riser height and flight goings
- • Pitch and Blondel values
- • Estimated minimum headroom
- • Landing geometry and parts schedule
Example with numbers
Worked example: a half-turn layout
A 2,800 mm climb can start with 16 equal risers divided between two parallel flights. The landing, gap, and opening must then be checked together.
Starting measurements
- • Floor-to-floor height: 2,800 mm
- • Two 900 mm-wide flights
- • Landing depth: 900 mm
Starting result
- • 16 risers at 175 mm
- • Target going: 270 mm
- • Blondel value: 620 mm
- • Pitch: about 33°
Illustrative example only: verify the opening, headroom, structure, and applicable rules before building.
What to have reviewed
The current half-turn export summarizes the design for review. A qualified builder or designer still needs to resolve support, landing construction, stringer connections, guarding, and local regulatory requirements.
Guides for this calculation
Take the right measurements and check what limits the plan before you finalize your stair.
Layouts
Planning a half-turn staircase
The dimensions to check when designing a 180-degree half-turn (U-shaped) staircase with two flights: flight balance, landing size and arrival direction.
Planning
Stair headroom: what to check before building
How stair headroom depends on the floor opening, slab thickness and finishes, and the layout mistakes that cause clearance problems near the top of a flight.
Renovation
Stair measurements to take before a renovation
The room, opening and floor measurements to collect before redesigning a staircase, from finished heights to obstructions and slab thickness.
Common questions
What is a half-turn staircase?
It is a U-shaped stair with two flights traveling in opposite directions, connected here by a rectangular landing.
Why compare both flight lengths?
The available length for each flight affects its going and pitch. Comparing both prevents one flight from becoming the limiting geometry.