Software is the sexy sauce of the digital economy of the last generation. However, somebody still has to keep the roof from leaking.

And Kevin Krolczyk, who left the software world in 1993 to buy the former Dalbec Roofing with his wife, Michele, has proved that experience and innovation can advance a 1950s-vintage business in an industry where not many local-legacy roofers survive.

"Kevin is a good guy, and he's focused and pretty driven," said Bob Dalsin, a competitor and longtime president of century-old John A. Dalsin & Son of Minneapolis. "Kevin also has a reputation for being honest and not cutting corners."

When the Krolczyks bought Dalbec from Michele's ­parents, three-quarters of its work was new construction of commercial roofs made of rubber or built-up asphalt for general contractors. That business parrots construction industry swings. And general contractors typically withhold 10 percent of the value of a job until complete. And that doesn't play to long-term customer relationships and smooth revenue streams.

"We just try to help people make their roofs last longer," said Kevin Krolczyk. "We saw a lot of roofs that didn't last long could have been preserved. I thought there was a better way to take care of some of them."

In 2012, the Krolczyks ­jettisoned the Dalbec name to become "Mint Roofing." It reflects the evolution from a roofer that primarily installs new-construction roofs to a 90 percent focus on prevention, maintenance and reroofing for long-term customers.

The industry says the cost of repairing a leak is 2.5 times higher than the cost of an annual maintenance program that detects problems, before the roof starts gushing water into ceilings and walls. And it's generally smarter to spend up to 10 percent of the cost of a new roof to keep an old one going a few more years.

"We were definitely ­proactive on this trend," Kevin Krolczyk said.

The Long Lake-based company, which employs up to 65 office and field personnel during good-weather months, has doubled its roof-management portfolio to 500 clients since the Great Recession, thanks largely to the maintenance program and repeat business. And revenue last year approached $7.5 million, nearly four times what it was when the Krolczyks bought the business in 1993.

Dalbec Roofing was founded in 1950 by the late Lester Dalbec.

The late Doug Zumbusch, Michele's dad, was a Dunwoody Institute-trained roofer and sheet metal worker who went to work for Lester Dalbec, his brother-in-law.

Doug and Bernice Zumbusch, who died several weeks ago, bought the company from Lester Dalbec in 1980. They moved it from Minnetonka to a small building in Long Lake. They lived the business. They installed an office on their 30th anniversary. The after-hours roof-emergency phone line was in their home.

Kevin and Michele Krolczyk, now both 50, met in college 30 years ago and married in 1988. Kevin was a business major with a knack for computers. He worked two summers for Dalbec, tearing off roofs and then for a year after school, converting the office and accounting from spiral notebooks to an IBM personal ­computer. But Krolczyk declined to take a permanent position after college. "I left Wisconsin to get away from my family construction business and I wasn't sure that [Dalbec] was what I wanted to do the rest of my life," Kevin Krolczyk recalled. Instead, he took a position with a software company that automated small businesses.

Kevin Krolczyk got along well with his father-in-law, who also wanted an exit strategy by 1993. Kevin and Michele then agreed to buy Dalbec, expecting to be mentored for a couple of years. However, Doug Zumbusch, 60, suffered a massive stroke shortly after Kevin Krolczyk signed on. He returned to the office a year later to tell Kevin to take over his desk.

Doug Zumbusch was a hands-on tradesman-turned-boss who made his own calls. Krolczyk is confident, but he's more collaborative. The day after Krolczyk took over for ailing Zumbusch, somebody asked Kevin if he thought he was up to it.

"I said, 'Damn right,' " Krolczyk said. "But I was also smart enough to know I couldn't do it myself.''

The Krolczyks paid about $350,000, or about $2,800 monthly for a decade, for the company. Michelle recalled that was about four times their mortgage payment. They had to grow the business to make it.

Michele Krolczyk quit a corporate job to join the family business as the marketer about 20 years ago. The Krolczyks have raised three sons and built a business that grew from $2 million annually to $7.5 million with a growing client list.

Randall Haney, the administrator of the Parish of the Annunciation in south Minneapolis, said the multi-roof church-and-school complex once had several roofers in the file. And two leaky roofs several years ago. Mint, now the exclusive roofer, is re-roofing a small roof this month for $18,000 after a $130,000 large-roof redo last year.

"Mint was not the cheapest bid," Haney said. "But they asked the right questions about the roof and the issues … and gave good supporting documentation that I could confirm. Now, they come every year and inspect our roofs and give us a report and that way we can get on top of any necessary maintenance and pay a small price to maintain instead of a big price for damage and repair."