Standing 200ft above the ground, the last thing you need to be worrying about is being attacked by Peregrine Falcon defending its nest.
But that is just one of many factors the team changing 1,437 windows at Bucks County Hall has had to consider.
Bucks County Council’s Peter Edington is overseeing the £2 million project.
He said: “We had to think about their breeding season, which put restrictions on when we could be at roof level.
“We could not get up there before June and need to be away by January.”
The authority is undertaking the mammoth project, which attracted criticism for its huge costs, to bring the 1960s building up to date, reduce energy costs and improve staff working conditions.
Bucks-based contractor Hazlemere Group has been brought in to do the work, using 15,000 scaffold tubes, 55,000 fittings and 5,000 walking boards.
Company director Barry Matthews said: “I have lived in Aylesbury all my life and it makes a nice change for a local contractor to be involved in such a prestigious job.”
As not all the windows are the same size, the company has had to spend 8,600 man hours making them.
A lot of the work is also having to be done overnight so staff are not disrupted.
The project, which began in February, is now half done, with all the windows in the lower floors taken care of.
Mr Matthews’ firm is now focusing on the tower, with window replacement starting this week.
One of the problems with putting up such an enormous structure was the weight it would put on the weak ceilings of the lower Mezzanine floor. Mr Edington said: “Any significant load would go straight through the roof.
“We thought about coming through the roof of the café and taking the floor out, but that would have disrupted services.
“We have designed it so the load is well spread.”
A gap also had to be left for 100 abseilers to scale the building for charity last month.
With work going to plan, it is now hoped the weather does not hold up the team.
Mr Matthews said: “If it was too adverse we would have to stop working.”