Stair elements, ladders, lifts, elevators and ramps

Essential elements of a stair

A stair has the following essential elements:

• Step: one riser plus one tread; steps are the basic unit.
• Tread and riser: the tread is the horizontal surface (250-300 mm), the riser the vertical face (150-175 mm).
• Nosing: the rounded projecting edge of the tread (about 25 mm).
• Flight: an unbroken series of steps between landings (3 to 12 steps).
• Landing: a level platform at the ends of a flight or between flights; quarter-space or half-space.
• Going and rise: the horizontal and vertical measurements of a step or flight.
• Waist slab / stringer: the inclined slab or beam which supports the steps.
• Soffit: the underside of the flight.
• Handrail, baluster and newel post: the balustrade that protects the open sides; the handrail is about 0.9 m high.
• Headroom: the clear height above the steps (minimum about 2.0-2.2 m).
• Winder: a tapered step used to turn the stair in a restricted space.
• Pitch line: an imaginary line joining the nosings; its angle with the horizontal is the pitch.

        handrail
          /|  baluster
   newel /_|__
        |    |  nosing
  riser |____|__ tread
  ______|
   going <--->

Ladder

A ladder is a set of rungs (steps) fixed between two side rails, set at a steep slope (60-90 degrees). It gives access to lofts, roofs, water tanks and manholes, and is used for fire escape or maintenance. Fixed ladders are made of steel, timber or aluminium, with rungs 250-300 mm apart. A ladder takes little space but is steep, unsafe for children and the elderly, and not suitable for regular traffic.

   | |
   |=|  rung
   |=|
   |=|
   | |

Lift and elevator

A lift (elevator) is a mechanical device which carries persons or goods between floors in a vertical shaft by a car moving on guide rails. Main parts: lift car, hoistway (shaft), guide rails, counterweight, wire ropes, traction machine and motor in the machine room (or machine-room-less), control panel, safety gear and buffers, landing doors and a pit.

• Types by drive: electric traction, hydraulic and machine-room-less (MRL) lifts.
• Types by use: passenger, goods (freight), hospital (bed), service and observation lifts.
• Speed 0.5-1 m/s for low-rise and 1.5-2.5 m/s for high-rise buildings. Lifts are required in buildings of more than about 4-5 storeys (as per building bye-laws), and fire lifts in tall buildings.

  machine room
   [motor]
     |   |
   [CW] [CAR]
     |   |
     |   |   <- guide rails
   ---pit---

An elevator is the American term for a lift; both mean the same.

Ramp

A ramp is an inclined plane (without steps) connecting two floors at different levels; it carries wheelchairs, trolleys, bicycles, vehicles and stretchers.

• Slope: 1 in 12 for wheelchairs (up to 1 in 10 only for short lengths), and about 1 in 8 to 1 in 10 for goods trolleys and vehicles.
• Width at least 1.2 m (1.5 m in public buildings), with a level landing of at least 1.5 m x 1.5 m at the top, at the bottom, at turns and after every 9 m of ramp length (barrier-free design requirements).
• Handrails at 0.8-0.9 m on both sides, a kerb or edge protection, and a non-slip surface.
• Requires a long horizontal space: a rise of 1 m needs about 12 m of ramp.

        ______ upper level
       /|
      / | rise
 ____/__|
  length = 12 x rise