The $2.8 million job to fix and upgrade Auckland's Chancery shopping, dining and office precinct is on track to be finished around Christmas.
But maintenance issues mean not all the workers will leave the site until early next year.
Graeme Birkhead, Arrow International's northern director, said much of the work was already completed on the site where around 40 people had worked daily.
Arrow won the contract for one of the inner-city's largest building repairs and upgrades and started work late last year.
The block opposite Freyberg Place at the foot of the Metropolis Residences apartment block opened in 2000 but suffered leaky building issues for many years.
Birkhead said the job was not easy.
"Because of the challenges of working around all the existing people in there, it will be after Christmas that all the maintenance is completed," Birkhead said.
The shopping and office precinct is being painted 11 different colours after a new colour scheme was designed, he said, to freshen the place up and give the different precincts their own character.
"In leakies, you always find things you don't expect but the real challenge was working around the existing retailers and restaurateurs. We couldn't start early because people go there for breakfast nor could we work late as people are in the bars and restaurants around there. So that meant health and safety issues and how we got enough time in the day to do the job. That was the real challenge. It was more like keyhole surgery rather than open heart surgery - done in a tight time frame each day.
"We had to build bridges and platforms and protection over the top from the weather and underneath to protect the retailers and restaurateurs so the tradespeople were sandwiched in between - painters, carpenters, tilers, usual building trades people," Birkhead said.
In 2009, a report by building consultant Alexander and Co showed extensive repair work was needed.
Tony Allsop, of property managers and consultants Colliers International, said in July that the owners of properties there won $3.4 million for repairs from builders Multiplex and others.
The money had been paid last year after mediation, he said.