A facade is only finished when someone can reach it again

Every facade gets cleaned, inspected, resealed and eventually repaired. That is not a maintenance detail, it is a design condition: the envelope has to be reachable for as long as the building stands. When the access system is drawn at the same time as the envelope it disappears into the parapet. When it is added later it sits on the roof like equipment that arrived by accident.

Permanent or temporary

A permanent system stays with the building: a roof car running on a track around the perimeter, or davit arms socketed into fixed bases, with the platform stored when it is not in use. A temporary system is brought in for a campaign, hung from tie-back anchors and removed afterwards. The first belongs to buildings that need frequent access and want it invisible. The second belongs to buildings where access happens on a cycle of years.

What the structure has to give

• A load path for the suspended weight, resolved on the structural drawings and not on the roof after the fact.
• Tie-back anchor points on the facade, positioned so the platform stays against the envelope in wind.
• Track or base support at the roof, with the parapet detail that hides it.
• Clearance for the platform to pass every projection, canopy and setback on the way down.

When the envelope is not a flat plane

A curved, faceted or inclined facade cannot be reached by a platform designed for a flat wall. The platform geometry, the restraint system and sometimes the track itself have to be designed for that specific envelope. This is the case where deciding late is most expensive, because the geometry that makes the building distinctive is exactly the geometry that a catalog platform cannot follow.

To get an access system proposed: elevations, the roof plan and a section through the envelope. What comes back is the system, its anchor layout and the maintenance plan that says how every square metre is reached.