Imagine covering the area of a city postcode in tiles little larger than thumbnails and you get some idea of the latest, greatest and possibly final challenge facing the fabled administrator of São Paulo’s most iconic building.

Affonso Celso Prazeres de Oliveira has managed the colossal Edifício Copan since 1993, turning the once run-down magnet for drug-dealers and prostitutes into what one resident calls “the coolest building in Latin America”.

In that 23-year period, the former chemical engineer has faced and overcome countless problems, including crime, fraud, drought and recession, with such success that the Copan – a city within a city of 5,000 residents – is now cited as a possible model for the rejuventation of central São Paulo.

But this classically curvy concrete structure is itself in need of a facelift. Designed by Oscar Niemeyer in the shape of the tilde above the “a” in São Paulo, the Copan celebrated its 50th birthday last year with middle age starting to take its toll.

The Copan’s curves. Photograph: Ricardo Campo/Getty Images

Some of the small square beige tiles that cover the surface of the 35-storey building have fallen on to the busy streets below. To prevent injuries or worse, Don Affonso – as the adminstrator is universally known – has covered the structure in a fine mesh. But he wants a longer-term solution.

It’s not me that has the power, it is the building. I treat everyone equally. That’s the most important thing Don Affonso

He has applied for permission to replace the approximately 72 million tiles that cover the 46,000-square-metre exterior of the building – a job he estimates will take about four years.

But the plan has run into obstacles. City authorities have so far turned down the application because Don Affonso cannot guarantee he will replace like with like – a condition for any change to this heritage structure.

“I want to restore the building but they won’t approve the plans, so I am taking the government to court,” says the clearly frustrated administrator. “The problem is that the original factory no longer makes these tiles. I have organised a meeting of other producers to try to find one that meets the exact specification that the city insists upon.”

Don Affonso – who is approaching 80 years of age – aims to get permission for the re-tiling before he retires next year.

The Copan building is in the shape of the tilde above the “a” in São Paulo. Photograph: Alamy

Given his track record, few would bet against him getting his way. Among the residents of the 1,160 apartments, the administrator has a quasi-mythical reputation for getting things done.

“This is the best-administered building I know,” said Pedro Herz, a bookshop magnate who has taken over two apartments on the 32nd floor. “When nothing else works in Brazil, Copan works.”

Herz takes some of the credit for this. As a member of the residents’ committee, he proposed that every tenant pay one cent per square metre so that Don Affonso could have a salary for doing a job that had previously been voluntary. “He cares for the building 24 hours a day, 365 days a year. Copan is like his child,” says Herz. “He wants to retire, but we won’t let him.”

Semi-mythical status … Don Affonso displays samples of replacement tiles. Photograph: Jonathan Watts/The Guardian

Giovanni Bright, a professional magician who has lived in the building for 35 years, says the transformation has been spectacular.

“When I first moved in, I used to be ashamed to tell people I lived here. It was a mess. There were power cuts. Topless women did drugs on the roof. Anyone could go anywhere,” he recalls. “Now, I believe it is the coolest building in Latin America. It’s safe, it’s central and there is so much attention on this building that it helps artists like me to get more visibility.”

Galleries and restaurants have opened up inside Copan, which has its own postcode, and the building is now so famous that it generates revenue from photo and video shoots. Last month, U2 paid to pose here. Don Affonso says the money will be used to pay the remaining 8m reais needed for renovation.

How the transformation came about is a matter of some controversy. After Don Affonso took over, he restricted access to the building and worked with police to eject residents involved in illegal activities. Asked how he turned things round, he replies with one word: “Force.” But he reject accusations of dictatorial tendencies. “That’s a joke. It’s not me that has the power, it is the building,” he says. “I treat everyone equally. That’s the most important thing.”

A range of residents have been attracted to apartments that range widely in size and price, with average rents that are relatively modest considering the central location. For those opposed to more exclusive gentrifying trends, the Copan serves as an example to the 70 or so buildings in the central area that have been empty or under-used for decades.

“It ought to be a model. Unfortunately, today’s architects don’t think like Niemeyer,” said Kleber Simões, a resident on the 13th floor better known as the DJ KL Jay. Born to a relatively humble mixed-race family on the outskirts of the city, Simoes says the diversity of Copan makes him feel comfortable. “This is a build for artists. There is a great energy. I’d be happy to spend the rest of my life here.”

The same is likely to be true of Don Affonso. He has lived in the building for all of its history, so even if he retires as planned a year and a half from now, he will be able to watch the re-tiling operation and to maintain an attachment that has dominated most of his life.

“My relationship with this building is a passion,” he says. “I am more jealous of it than I am of my wife.”

Guardian Cities is in São Paulo for a special series of in-depth reporting and live events. Share your experiences of the city in the comments below, on Facebook,Twitter and Instagram using #GuardianSaoPaulo, or by email tosaopaulo.week@theguardian.com