What is the minimum lift car size for wheelchair access under Part M?

Approved Document M requires a minimum lift car internal size of 1100mm wide × 1400mm deep for wheelchair access in new buildings. The car door must be at least 900mm clear opening width. BS 8300:2018 recommends the same minimum dimensions. For buildings where stretcher access is needed, the car depth should be at least 2100mm.

How do I determine the shaft size for a passenger lift?

Shaft dimensions are calculated from the car size plus clearances for the guide rails, counterweight, door mechanism, and safety equipment. Typically, the shaft is 400-500mm wider than the car (200-250mm clearance each side) and 500-550mm deeper (200mm for the door mechanism plus 300-350mm for the counterweight). The exact dimensions vary by manufacturer, so these are indicative for early design stages.

When is a firefighter lift required in the UK?

BS 9999 and Approved Document B recommend firefighter lifts for buildings with a floor more than 18m above fire service access level. The Regulatory Reform (Fire Safety) Order 2005 may also require them. Firefighter lifts must comply with BS EN 81-72, have a minimum car size of 1100mm × 2100mm, independent power supply, and special firefighter controls on a separate circuit.

What pit depth is needed for a passenger lift?

Pit depth depends on lift speed and load rating, governed by BS EN 81-20:2020. Typical requirements are 1200mm for lifts up to 1.0 m/s, 1400mm for 1.6 m/s, and 1600mm or more for higher speeds. Reduced pit solutions are available from some manufacturers using buffers and alternative safety gear, but these must be approved by the notified body.

How many lifts does my building need?

The number of lifts depends on building population, floors served, and acceptable waiting times. BCO Guide to Specification recommends average waiting times under 25 seconds for commercial offices. A traffic analysis (using tools like CIBSE Guide D) is recommended. As a rule of thumb, one 13-person lift serves approximately 200 people in a 6-storey building with acceptable wait times.

Lift Sizing Calculator — Car Dimensions & Shaft Size per Part M

How We Calculate This

This calculator determines passenger lift car dimensions, shaft size, and capacity based on UK Building Regulations Approved Document M, BS EN 81-70:2021, and BS 8300:2018.

Car sizing

The minimum car size is determined by accessibility requirements and expected usage. Part M requires 1100mm × 1400mm for wheelchair access with a 900mm clear door opening. Larger cars (1100mm × 2100mm) are needed for stretcher provision or firefighter lifts.

Shaft dimensions

Shaft dimensions are calculated from the car size plus clearances for machinery:

Width: Car width + 250mm clearance each side
Depth: Car depth + 200mm (door) + 350mm (counterweight)
Pit depth: 1200-1600mm depending on lift speed
Headroom: 3600-4200mm above top floor landing

Load rating

Lift load ratings follow BS EN 81-20. A standard 8-person wheelchair-accessible lift has a 630kg rating. A 13-person stretcher or firefighter lift is rated at 1000kg. The rated load determines motor size, counterweight, and structural support requirements.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.

Lift Sizing Calculator - Part M Passenger Lift Car & Shaft Dimensions