Every tall facade eventually needs a crew on it — glass to wash, seals to inspect, panels to replace, a leak to trace. The question is how the crew gets there, and the answer almost always comes down to two families of equipment: a temporary facade maintenance cradle, rigged for the job and removed afterwards, or a permanent BMU (building maintenance unit) built into the building. Both hang a platform on the facade; everything else about them is different.

 

The choice is not about which is “better” — it is about which fits the building, the budget and the schedule. Get the decision right and the building is cheap to maintain for decades. Get it wrong and you pay twice: once for access you do not need, or once for access that is never there when you need it.

 

 

 

A temporary cradle — a suspended platform rigged from the roof for a specific contract — is the default for cleaning and maintenance contracts, retrofit work and one-off jobs. The equipment is rented or bought, rigged over a few days, worked, and dismantled. There is no permanent structure on the roof, no long-term capital cost, and the same platform can serve a different building next month.

 

The trade-offs are the mirror image. Every job pays the setup cost again: rigging, inspection, dismantling, transport. And a temporary platform is only as good as the roof it hangs from — parapets, glazed roofs, weak structures and awkward setbacks can make a simple job expensive or impossible. For a building that needs access twice a year, temporary is usually right. For a building that needs it twice a week, it is the wrong bill every time.

 

 

 

A permanent BMU is designed, engineered and installed as part of the building's maintenance system. The family includes rail track units that travel the length of the parapet, telescopic jib machines that reach over the edge from a short rail, traversing trolleys for spot access, and davit systems. Once installed, a BMU puts a cradle on the facade in minutes, whenever it is needed, with no rigging crew and no repeated setup cost.

 

That convenience has a price. The machine is a capital investment, it needs the roof structure to carry it, and it must be maintained and inspected for its whole life. But run the arithmetic over a building's life — cleaning cycles, inspections, minor repairs — and the permanent machine usually wins once the work is frequent enough. For scale, Powerston's PB101 roof track BMU reaches a maximum lifting height of 450 m at up to 12 m/min, which covers essentially every high-rise maintenance regime.

 

 

 

Height matters, but not the way most people think. A very tall building needs a very long rope and a serious rig, which pushes toward permanent — but a 60-metre facade that needs weekly cleaning may still justify a BMU while a 150-metre facade cleaned annually might not. Frequency is the bigger driver.

 

Geometry comes second. Measure the parapet, the setbacks, the roof plant, the atriums and the steps in the facade. A flat roof with a clean parapet suits a rail track BMU beautifully; a crowded roof with plant rooms in the way pushes you toward a telescopic jib or fixed davits. And listen to the structural engineer: the roof has to carry the counterweights or the anchors, and that constraint can rule out options no brochure would mention.

 

Then there is the building's own logic. Glass-heavy facades need frequent washing, so they usually deserve permanent access. Facades with complex geometry or heavy maintenance needs — hospitals, labs, hotels, towers with external blinds — pay for a BMU fastest. A simple sealed wall that needs almost nothing can get away with occasional rented access for years.

 

 

 

Whichever family you choose, the equipment hangs people over the street, so the safety rules are the same. Wind limits stop work when the machine says stop. The crew works clipped to independent anchorage. The equipment — temporary or permanent — follows the same standards: EN 1808:2015 for suspended access equipment in Europe, and GB/T 19154-2017 (Window cleaning machine / building maintenance unit) for permanent BMUs in China. A permanent machine gets inspected on a documented schedule; a temporary one gets inspected before every job and every shift. Neither is negotiable.

 

 

 

An access system is a machine, and machines need care. A BMU's rails, trolley, jib, hoists and safety locks should be inspected per the manufacturer's schedule, with the brake and lock tests done under load and everything logged. A temporary platform needs the same discipline on a shorter cycle. Facade teams that treat their access equipment like scaffolding — check it when you remember — are the teams whose access equipment fails at the worst moment.

 

 

 

When should a building install a permanent BMU instead of renting cradles?

When the work is frequent enough that the repeated rigging and rental costs exceed the cost of owning a machine — typically a building with regular cleaning cycles, glass-heavy facades or ongoing maintenance needs. Frequency, not height alone, is the deciding factor.

 

Can a temporary cradle be used on a building with a difficult roof?

Sometimes, but the roof decides. Parapets, glazed roofs, plant rooms and weak structures can make temporary rigging expensive or impossible — at which point a permanent BMU with engineered anchors may be the cheaper answer over the building's life.

 

What is the maximum height a facade cradle system can serve?

Practical systems reach several hundred metres. Powerston's PB101 roof track BMU is rated to 450 m maximum lifting height at 0–12 m/min — beyond the needs of nearly any real building.

 

Does a permanent BMU need its own maintenance plan?

Yes, and it should be on paper. Rails, trolley, hoists, safety locks and controls all need scheduled inspection and testing, with records kept. A BMU that is not maintained is a BMU that will eventually fail in front of the building it was installed to protect.

 

 

 

Powerston builds both sides of the argument — temporary suspended platforms and permanent BMUs, including rail track units, telescopic jib machines and traversing trolleys. Send the roof drawings, facade photos and your cleaning/maintenance schedule through powerston.com, and the team will show you the cost comparison, not just a price list.