Wagner Roofing owner and chief executive Chuck Wagner is a hands-on architecture buff. His wife, Sheila, is a no-nonsense administrator. (Bill O'Leary/The Washington Post)

Many entrepreneurs make it a point to keep their business and personal lives separate.

And then there’s Sheila and Chuck Wagner.

Sheila is a no-nonsense administrator who is Mrs. Inside to Chuck’s Mr. Outside at Wagner Roofing, a 100-year-old company specializing in historical preservation. Their division of labor is an example of what happens when a family business gets it right. They built the company into a $12 million-a-year enterprise with profit margins easily exceeding 10 percent.

“We complement each other,” said Sheila, sitting at her desk in their Hyattsville headquarters. “I am behind the scenes helping keep all the parts moving so he can do what he does best, which is seeking out jobs. As someone said, there is nothing without a sale.”

Chuck has literally climbed all over the nation’s past, from Washington National Cathedral to the Old Post Office and Clock Tower, from Mahan Hall at the United States Naval Academy to Thomas Jefferson’s University of Virginia.

Company President Dean Jagusch, seen here inspecting a missile on display in a Maury Hall stairwell in Annapolis, is expected to one day take over the century-old company. (Bill O'Leary/The Washington Post)

The 71-year-old architecture buff knows the back story to many landmarks. He will tell you a compact car could fit in the gutters on the cathedral.

He says it’s a shame you can’t see the stamped copper crests atop the Daughters of the American Revolution Constitution Hall (1929) from the street.

He knows that Georgetown’s Tudor Place began with an $8,000 gift from George Washington, and that students at Holy Redeemer Catholic Church in Kensington lined up to touch the cross before it was hoisted atop its steeple following the 2012 derecho.

“We are in the business of preserving history,” Chuck said.

Sheila oversees human resources, bookkeeping, billing, scheduling, purchasing and the million and one other unglamorous details that make for a successful business.

One corner of her compact office is a mini-museum, filled with tools and materials such as slate rippers, wood mallets and copper sheaths that helped the company over the past century.

In addition to being historical junkies, Chuck and Sheila are big cheerleaders for their lucrative little firm, publishing glossy coffee table books and calendars that highlight the various historical jobs they have taken on. There is even a quarterly in-house newsletter called Rooflines.

Wagner Roofing has 55 employees, 10 of whom are salaried and the rest of whom are skilled hourly workers who can earn up to $100,000 a year. Those workers get two weeks’ vacation, health care, 401(k) matches and free education such as English classes, as long as it helps them do their jobs.

“One of the keys to our success is retaining employees,” Sheila said. “It’s expensive to find people who can do this work. We treat them well, and so they stay.”

Keeping them out of harm’s way also helps. The size of employees’ year-end bonuses depends on the company’s safety record. The dollar amount is reduced each time an independent inspector spots a lapse on a job site. Safety saves on the company’s insurance bill, which approaches $300,000 a year.

Wagner Roofing performs around 300 projects a year, from Charlottesville to Charleston, and from the West Indies to West Virginia. Most of those are in the Washington area.

Preservation accounts for around three-quarters of revenue. The rest is divided between commercial, residential and thousands of service jobs for all kinds of roof maintenance.

I met Wagner when I asked for an estimate on my 80-year-old slate roof.

Otto Wagner, Chuck’s grandfather, founded Wagner Roofing in 1914. He was a first-generation immigrant from Germany. After Otto died, his son, Jack Wagner Sr. (Chuck’s father), took over in 1937, giving up a track scholarship to American University to rescue the family business.

When Jack went to Italy in World War II, his wife, Evelyn, ran the company.

“My mother would send him letters, estimating jobs through the mail. She told him about new customers. She was tough.”

Jack Sr. carved his own niche in the roofing business by working for insurance companies, who came to trust him and gave him their repair work for clients.

“There was no deductible back then, so insurance companies would call and say, ‘just fix it,’ ” Chuck said.

The company did well, and Chuck and his older brother, Jack Jr., grew up with their mom and dad in Chevy Chase. Chuck went to St. John’s College High School.

Jack Jr. stepped in to take over the company after their father suffered the first in a series of heart attacks in 1961. Chuck joined his brother in the company after graduating from LaSalle University.

“We were partners for 25 years,” Chuck said. “He was my mentor.” Early on, the brothers noticed that one company had cornered most of the slate roof business, so they decided that was an area for growth.

When Chuck and Sheila bought out his brother in 1990, the company enjoyed a strong reputation but wasn’t exactly flush with cash. Sovereign Bank was asking about its $250,000 loan.

Sheila took over.

“I called the bank and told them if they gave us one year, we would pay back that entire loan,” she said. “And we did. I took no salary. Chuck cut his salary in half. Everyone else took a pay cut.”

Sheila attacked stacks of invoices that had not been sent to clients, trying to boost the cash flow. Chuck slowly took the business into historical preservation work, pivoting away from working with builders. Chuck also sought out property managers, hoping to create relationships with people who managed multiple buildings.

“I was more into repeat business,” Chuck said.

His first preservation job was fixing the slate roof at St. Mark’s Episcopal Church. Other churches began to call.

“People started calling me ‘Church Chuck.’ ”

Smartly, he began joining historical boards, where he could schmooze with architects and the preservation crowd: Architectural Commission for the Episcopal Church Diocese, Tudor Place Foundation, the National Building Museum, the National Trust for Historic Preservation, District of Columbia Preservation League.

Today, the company’s back lot harbors 26 trucks. Over in the corner is the slate yard, filled with thousands of pieces of salvaged slate and tile, including the remnants of the terra-cotta roof at the Congressional and Columbia country clubs and the slate roof at the Maryland State House. The company’s metal shop is filled with specialized machines that can cut and bend metal to replicate 100-year-old decorative flourishes that grace hundreds of buildings throughout the Washington area and beyond.

Shop foreman Manny Cerrito mans a soldering iron, re-creating history as he painstakingly shapes, cuts and solders 12 separate pieces that will become one of the 150 copper fascia ornaments to be affixed to Maury Hall at the U.S. Naval Academy.

Last year, the Wagners hired Dean Jagusch, in his mid-30s, who is the company president and is expected to take over one day. Jagusch has enabled Chuck and Sheila to pull back from the business a bit, allowing them to team up on things other than work.

They were last seen in New Zealand, where the husband-and-wife roofers went hang gliding — still preferring to see things from above.