How we fixed it: Re-roofing the Castalia building, The Hague, Netherlands

What was your approach?
We used rope access techniques to patch repair the roof, install a layer of insulation and a Kalzip aluminium skin, then build a permanent abseil system on the roof ridges designed to allow permanent, long-term access for maintenance.

The Dutch contractor, JP van Eesteren, filled the V-shaped gap between the roofs with scaffolding, which gave us a flat surface to store materials and abseil from to reach the outside surfaces.

The permanent access system is accessed via the flat lower roof located between the two pitched roofs. A specially-adapted electronic climbing trolley, typically used for window cleaning cradle systems, climbs a 25m-long rail up to the ridge line from which trained abseilers can attached their ropes.

What was the biggest challenge?
This was the first time rope access had been used on such a tall building in Holland, so the Dutch were very stringent on safety and we were asked a lot of questions. The Castalia’s roof is also very bespoke and our team had to undergo a four-day training course to become approved Kalzip installers.

Couldn’t the Dutch have done the abseiling?
Operatives could have undergone a five-day rope access training course, but they still would have needed a trained supervisor, which requires around three years’ training.