How much space does a loft staircase need?

A straight flight needs about 2.6m × 0.9m floor opening (2.34m²). A winder/L-shape needs 1.8m × 1.8m (3.24m²) but fits into a corner. A spiral staircase needs the least floor area at 1.6m × 1.6m but may not comply with Part K for a habitable loft room.

Can I use a space-saver staircase for a loft conversion?

Space-saver (alternating tread or paddle) stairs are only acceptable for a single habitable room in the loft. If you have two or more rooms (or a bathroom), you need a standard staircase complying with Part K. Building control will advise on your specific situation.

What is the maximum staircase pitch for a loft?

Part K allows a maximum pitch of 42° for a standard staircase. Loft conversions may use an alternating tread stair at steeper pitches if only serving one room. The rise should be 150-220mm and the going 220-300mm, with 2×Rise + Going = 550-700mm.

Where is the best position for a loft staircase?

The ideal position is above the existing staircase, rising in the same direction to minimise disruption and structural alterations. Alternatively, over a hallway or large bedroom. The staircase must discharge onto a landing with a protected escape route — usually the existing landing.

Do I need to fire-protect the staircase?

Yes. The loft staircase must be within a protected enclosure with fire-rated doors (FD30 self-closing) at every level. The existing staircase below must also be enclosed to create a protected escape route from the loft to the final exit door. This is a Part B requirement.

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Loft Staircase Space Calculator — Floor Opening & Area Lost

Calculate the floor opening size and area lost on the floor below for different loft staircase types: straight, winder, spiral and space-saver.

Staircase Type

Floor-to-Floor Height

Finished floor to finished floor

Landing Width

Landing at top/bottom of stairs

How We Calculate This

This calculator determines the floor opening size and area impact for different loft staircase types.

The formula

Opening Area = Opening Length × Opening Width

Risers = ceil(Floor-to-Floor Height / Rise Height)

Pitch = atan(Height / Total Going) in degrees

Typical opening sizes

Straight flight: 2.6m × 0.9m
Winder/L-shape: 1.8m × 1.8m
Spiral: 1.6m diameter
Space-saver: 2.2m × 0.6m

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.