YBOR CITY - It's still possible to imagine the three floors and window-lit basement of the J. Seidenberg & Co./Havana-American Cigar Factory filled with 19th century workers.

The building, 2205 N. 20th St., retains its plain brick exterior and steep concrete steps. But inside it's a study in 21st century technology and the latest in urban planning.

WilsonMiller, a planning, design and engineering company, relocated its local operations from two Channel District offices to the renovated Seidenberg building in June. The Naples-based company plans an open house Aug. 16.

"We needed 35,000 square feet," said Dave Kemper, senior vice president and manager of the Tampa office. The property also offered 135 parking spaces.

Moving 120 employees into an 1894 cigar factory had its challenges. Kemper said the company could have leased space in a glass, boxy office building.

"Then we wouldn't have faced any uncertainty," he said. "But when you tackle an old structure like this you don't always know what you're getting."

Although empty for a few years before WilsonMiller began its $3.5 million renovation, the Seidenberg building had an earlier upgrade when the Ybor City Brewing Co. began operating there in 1994. The company closed the bottling plant in 2003, but brewery founder Humberto Perez still owns the building.

The brewing company had replaced about 75 percent of the tall windows, characteristic of cigar factories because workers needed extensive light to roll delicate tobacco leaves.

Seidenberg is Ybor's second-oldest brick cigar factory. Manny Leto, Ybor City Museum Society director, said the oldest - which became an office complex about five years ago - is the 1886 Ybor Square/V.M. Ybor at Ninth Avenue and Avenida Republica de Cuba.

"It's finally coming around - seeing these old structures take on a new life," Leto said.

WilsonMiller had to follow Barrio Latino Commission guidelines, which normally apply to historical preservation of a building's exterior, because tax breaks were sought for the renovation.

"This building wasn't in too bad shape," said architect Stephanie Ferrell, a consultant on the project. "But it was important to keep the basic look as offices were added to the open space."

A big challenge was restoring the century-old brick, which not only was scorched in spots by a nearby fire in 2000 but also had been coated in places by black adhesive used on shutters and other items. Kemper said a nonabrasive cleaner was used.

He said most of the wood floors could not be salvaged.

The west entrance facing 12th Avenue provides the best glimpse of how the factory once looked. A wood floor remains, and a wide wooden staircase leads to the second and third floors.

The Seidenberg building doesn't have a brick inlaid sign like most of Tampa's two dozen remaining cigar factories. Because most people remember the factory as the Ybor City Brewing Co., Kemper said he will try to keep the rooftop sign left by the microbrewery.

Mayor Pam Iorio is scheduled to attend WilsonMiller's ribbon cutting from 8:30 to 9:30 a.m. Aug. 16. The open house is from 4:30 to 8:30 p.m. For information, call (813) 223-9500.

Reporter Janis D. Froelich can be reached at (813) 835-2104 or jfroelich@tampatrib.com.