Like many buildings in the French Quarter, the fortunes of the house at 520 Royal St. have ebbed and flowed with those of the neighborhood around it, moving between a lavish home for the upper crust and almost a crumbling ruin.

But with the old mansion now owned by the Historic New Orleans Collection and undergoing a $30 million rehabilitation, preservationists hope to see it returned to the height of its historic glory — a place where, in the future, people can walk through a piece of New Orleans' past.

The effort, which began in earnest in 2014 and should be complete in late 2018, has been extensive: an excavation of the building grounds, a reworking of the masonry of the original construction and intricate plans to insert modern touches that won't harm the integrity of the historic structure.

When the work is complete, the 200-year-old house, its flanking buildings and a new, 16,000-square-foot flexible exhibit space to be built at the back of the property will include a shop, a cafe and exhibits centered on New Orleans art and history. It will be open to the public — a full-size historical artifact put to modern use.

The house's history in some ways has paralleled that of Louisiana.

In the early 19th century, the Louisiana Purchase brought New Orleans into the United States and opened up the city as a magnet for entrepreneurs and craftsmen.

One of those drawn to the city was François Seignouret, a Frenchman who came to New Orleans in 1808 and began business as a furniture maker.   

Seignouret's furniture was — and is — highly prized, and his renown grew. Not long after the 1815 Battle of New Orleans, in which he fought, he began his most ambitious building program to date: a house on Royal Street.

Seignouret planned a beautiful three-story house, with the first floor serving as a place to conduct business; a versatile courtyard; and a terraced roof onto which he and his family could retire to escape the noise and smells of the street below.

The house was built in 1816, and Seignouret's career continued to flourish. He expanded his business from furniture into wine importing. But while the house remained on Royal Street, Seignouret didn't.

He returned to France to oversee his wine business, but his heirs remained in the house for several decades, even after his death in 1852.

In 1865, the heirs sold the house, and in 1870 it was bought by another importer, Pierre Brulatour, who owned it until 1887.

The house is now known as the Seignouret-Brulatour House after these two key 19th century owners.

Brulatour was followed by a succession of owners in the latter 19th and early 20th centuries, until 1918, when it was bought by American tobacco magnate William Ratcliffe Irby.

Irby had the house extensively remodeled — including installing an organ on the third floor — as a luxury residence to which he intended to move. He also allowed many members of the French Quarter's burgeoning bohemian scene to spend time at the house, turning it into the headquarters for the Arts and Crafts Club of New Orleans. Sadly, Irby died in 1926 without ever having lived in the house.

The next major change came just after World War II, when a new industry came to town: television. The city's first TV station, WDSU, took possession of the house, and it served as the station's headquarters until the mid-1990s. For many years, viewers of the popular "Midday" show could watch broadcasts from what was known as the "Brulatour courtyard." 

When the Historic New Orleans Collection — whose headquarters building is just across the street — obtained the house after Katrina, it quickly decided it wanted to preserve as much of the old mansion's historic fabric as possible, while making it safe and comfortable for 21st century visitors. 

Making a two-century-old building true to its roots while usable in 2018 is a complicated process.

"Work really began in earnest in 2014," said HNOC Deputy Director Daniel Hammer. "A lot of work was done to shore up the building."

Hammer said the house's original materials and features show how builders in the early 19th century coped with the challenges of making a livable, durable house in the Louisiana climate.

Doors and windows facing the street and the courtyard could be opened at the same time to increase ventilation. The soft, local bricks used in the entire house absorbed moisture from the ground and conducted it upwards. The mortar and plaster in the walls were "breathable" and allowed the moisture to be diffused, especially on the ground floor.

However, subsequent renovators used modern paints and plasters, and those held the moisture in. The addition of air conditioning in the 20th century only exacerbated the problem. That moisture buildup damaged the house's bricks.

When experts began to look at the walls a few years ago, they discovered that many of the bricks were in bad shape. Many needed to be relaid, some to be replaced.

The air conditioning had to be updated in a way that wouldn't just repeat the moisture problems of the past, while also making the house comfortable for modern history buffs to stroll through.

"It all had to be fit in very carefully into a pretty limited space," Hammer said. "The amount of work that has gone into this building so that it's a modern museum as well as true to the history of the building is remarkable."

When the project is complete, the property will be divided into two parts, separated by the courtyard. The historic main building will house a permanent exhibition on the history of the French Quarter, as well as exhibits on the architecture and archaeology of the property. At the rear will be a newly built facility with three gallery spaces for changing exhibitions.

The first exhibition planned will examine New Orleans' modern art over three decades up to the Post-Katrina period. The exhibit is being guest-curated by Jan Gilbert.

The building is expected to open next year as the city celebrates its 300th birthday.

"It was always our goal that the building would be available for public enjoyment," said Priscilla Lawrence, the HNOC's executive director. "It's sort of a gift for the tricentennial year."

Follow Faimon A. Roberts III on Twitter, @faimon.