Sergey Kolesnikov and Igor Rybakov spent their summers in the early 1990s fixing rooftops around Moscow, a job that paid them about $500 a month.

The work gave the aspiring scientists, who were roommates at the Moscow Institute of Physics and Technology, Russia’s top research university, a chance to become entrepreneurs after the fall of the Soviet Union.

“We earned two degrees, one in physics and one in roofing,” Kolesnikov said in an interview at his central Moscow office.

The roofing degree paid off. Closely held Technonicol, the company they founded while in college, is now the country’s largest roofing-supply company, with a network of 700 distribution outlets across the country, 180 of them wholly- owned. The business had revenue of 59.4 billion rubles ($1.9 billion) in 2012, up 25 percent from the prior year, according to financial statements provided by Kolesnikov.

The company is valued at $2.8 billion, according to data compiled by Bloomberg, making the equal partners two of the youngest billionaires in Russia. Neither has appeared on an international wealth ranking.

“I always liked to solve puzzles, and to me business is a kind of puzzle,” Kolesnikov said. “Neither of us ever thought about earning money of such scale.”

Rebuilding Russia

The billionaires, both 41, had a well-timed entry into the market, catching the start of a wave of private homeownership and government upgrades to Soviet-era housing. The number of newly built private homes in Russia almost doubled to 205,000 from 2002 to 2012, according to data from the Federal State Statistics Service, and new apartment units increased more than two times during the past decade to 838,000.

In the past five years, the government has spent more than $7 billion improving the country’s housing, according to the State Fund for Assistance to Housing and Communal Services, and plans to spend an additional $3.3 billion on materials to upgrade 1.6 million apartment blocks that are still in need of repair.

Technonicol has a 30 percent share of Russia’s insulation market, according to Moscow-based Abarus Market Research. It derives 70 percent of its sales supplying repair work and the balance from new construction sales.