It is certainly no easy feat to keep a company running for nearly a century.

As any veteran businessman will tell you, it takes a mix of prudence, grit and a certain degree of risk- taking.

In the case of construction firm Woh Hup, it seems integrity - towards clients, employees and society - is another secret ingredient.

The privately held family business, which celebrates its 90th anniversary today, is behind some prominent features of Singapore's physical landscape, including Clifford Pier, Changi Prison and MacDonald House, but it largely keeps a low profile.

Quite remarkable for a group that boasts a staff strength of some 2,500 employees and generated revenue of about $900 million last year.

Family spokesman Eugene Yong is a third-generation member who serves as executive director in charge of corporate services covering human resources, health and safety and corporate social responsibility.

His father, Mr Yong Nam Seng, is the company's chairman, while his older brother, Mr Kim Yong Tiam Yoon, is deputy chairman.

To hear him tell it, the values that the company was founded on way back in 1927 are still very much alive today.

"We work hard and we build with integrity," says Mr Yong, 65. "If you do a project well, people will come back and ask you to do another."

In fact, that was how Woh Hup got its start.

After Chinese immigrant Yong Yit Lin arrived in Malaya in 1913 at the age of 16, he took on jobs as a tin miner, carpenter and clerk before venturing into construction.

He started a small business that focused on house repairs, charging fair prices for quality work while most in his trade were intent on generating quick profits.

His big break came in the 1920s when the Public Works Department in Seremban needed a contractor to build fences and garden gateposts for the British Resident of Negeri Sembilan, Mr Ernest Wolff.

His excellent workmanship won the attention of the Resident, who later moved to Singapore and asked Mr Yong to join him here and tender for government construction projects.

From there, his little company, initially named Woh Hup Yit, grew quickly. In 1933, it completed the construction of Clifford Pier. Then came Pearl's Hill Barracks, Changi Prison, MacDonald House, the former Bukit Timah fire station and Rochester Park, among other projects.

Over time, the company started to move into new ventures. In 1963, for example, it expanded from construction into development work, setting up a unit called Singapura Developments. This was sold to City Developments in 1981.

By the 1980s, at which time Mr Eugene Yong had already joined the business, Woh Hup was looking to expand further abroad. In 1985, it completed the Bank of Ceylon building in Sri Lanka, followed by another project in Bahrain in 1987.

Yet, even as it spread its wings, Woh Hup continued to take a prudent approach to business, Mr Yong notes.

"One of the reasons we didn't continue our development work in a large way was that we understood what the negatives were, and they were much larger financially," he says.

"There have been many development companies that have gone bust. The risks are higher."

Growth, but not at all cost - that has been the firm's strategy even during the leanest of times.

In a book commissioned for its 88th anniversary, the company recalled that business was particularly tough in the mid-1980s, when there was a prolonged construction slump.

There was one 15-month stretch when Woh Hup did not clinch a single new contract. Even so, it held on to all of its 200 staff throughout the downturn, despite the huge financial strain.

This is still a point of pride for the company, as are its charitable works and contributions, says Mr Yong.

Woh Hup Trust provides financial support for the elderly and underprivileged children. As part of the 90th anniversary celebration, the company is donating $3 million to charities, community projects and education.

Mr Yong himself has been chairman of the Riding for the Disabled Association of Singapore since 1996. He plans to step down soon to let someone younger take over.

When asked about major milestones in his career, he replies that he is "reasonably proud" of his charitable work over the past 20 years and his efforts "to be useful".

"In our society now, there is so much disparity. Helping people is quite fulfilling," he says. "It's not just about giving money but also about considering how to improve things while being practical."

As the company looks towards the years ahead, he says the values that have helped it succeed over the past nine decades have become even more pertinent today.

"Most businesses, of course, want to grow, but nowadays especially, circumstances are really difficult to predict. So you have to be prudent and not over-extend yourself," he notes.

"These days, it's so difficult to predict cycles, so it's more prudent to stay more in construction. We'd still do boutique developments - at least we know we can manage our risks. We want to do well in Singapore as a base, do a bit more work overseas and grow slowly."