Loft Ladder Sizing Calculator — What Size Loft Ladder Do I Need?

This calculator determines the correct loft ladder length, recommends a ladder type, and checks your existing hatch against the manufacturer opening sizes each ladder type needs. There is no statutory minimum loft hatch size in the UK — the figures below are manufacturer and industry norms, not Building Regulations.

Ladder length

Required ladder length = Floor-to-floor height + 100mm

The extra 100mm provides an overlap so the ladder extends slightly above the loft floor level, ensuring safe entry and exit.

Hatch sizing (manufacturer / industry norms)

• Manufacturer standard hatch: 562 × 726mm (e.g. Manthorpe GL250); ~530 × 530mm is the recommended practical minimum for personal access
• 2-section ladder: Fits a standard hatch; comfortable from about 726 × 566mm
• 3-section ladder: Very small minimum opening — the Werner 76003 quotes 380 × 400mm — so a standard 562 × 726mm hatch fits comfortably
• Concertina ladder: Fits a small opening from about 600 × 600mm

Don’t confuse the hatch opening with the in-loft storage clearance. A folded 3-section sliding ladder needs roughly 1120mm of horizontal space and about 710mm of headroom behind the hatch inside the loft (Werner 76003 figures) — that is the room for the stowed ladder, not the size of the opening you climb through.

None of these are statutory minimums — there is no Building Regulations minimum loft hatch size. A habitable loft conversion is different: it needs a fixed staircase to Approved Document K (maximum 42° pitch, minimum 220mm going) and, where there is no protected stairway to a final exit, an escape window to Approved Document B (clear openable area ≥0.33 m², at least 450 × 450mm, sill ≤1100mm above floor). A drop-down ladder and hatch are not adequate for a habitable room.

Clearance below hatch

The horizontal footprint when deployed is estimated as ladder length × cos(deploy angle), using a typical ~70° angle (cos 70° ≈ 0.342). This gives an indicative idea of the clear floor space needed beneath the hatch — always confirm against the swing and landing clearance in the ladder manufacturer’s installation instructions.

Floor-to-floor ranges

• 2-section: Up to 2.6m floor-to-floor
• 3-section: Up to 3.0m floor-to-floor (Werner 76003: 2.13–3.0m)
• Concertina: Up to 3.0m floor-to-floor