Cradle Lifts

Every glass tower has a problem that is rarely thought about until the building is finished: the outside has to be cleaned, and the sealant, glazing gaskets and cladding fixings have to be inspected and repaired for as long as the building stands. A cradle lift — also called a suspended access platform or building maintenance unit — is the permanent, engineered answer to that problem.

The platform hangs on wire ropes from equipment fixed to the roof. On a simple building that means davit arms sitting in sockets cast into the roof slab, moved by hand from one position to the next. On a large or architecturally complex tower it means a powered trolley running on a track, able to traverse the whole elevation and reach around setbacks and curves. We size the roof equipment to the building rather than forcing the building to accept a standard unit.

Everything above the platform is duplicated, because there is nothing below it. The platform hangs on its working ropes through traction hoists, and hangs again on an entirely separate secondary rope gripped by an independent fall-arrest device. If a working rope or hoist fails, the secondary system catches the platform within a few centimetres. Overload sensing, slack-rope detection, upper and lower limit switches and a manual descent for power failures are all standard rather than optional.

Local conditions decide the specification more than the catalogue does. Karachi's coastal air corrodes untreated steel quickly, so platforms there are galvanised or stainless rather than painted. Dust loading across Punjab means facades are cleaned far more often than in Europe, which raises the duty cycle the hoists must be rated for. And because wind is the single largest risk to a suspended platform, units are fitted with wind-speed monitoring that stops work before conditions become dangerous.