By Candace Taylor

Aug. 23, 2018 10:30 a.m. ET

Antiques dealer Michael Pashby specializes in 17th- and 18th-century furniture. His wife, Sandra Amann, an art conservator, focuses on modern and contemporary works.

When superstorm Sandy sent an 80-foot-tall tree crashing through the roof of their weekend home in rural New Jersey, they seized the opportunity to meld their styles in redoing the circa- 1930 stone-and-timber home.

Now, after a multiyear renovation that cost roughly $750,000, Mr. Pashby, 67, said that “parts of it are new, but they blend in perfectly.”

The couple first saw the Stone House, as it is known locally, while boating on Highland Lake, about 50 miles from their primary home on Manhattan’s Park Avenue. “It looks really quite

lovely from the water because it’s so much stone,” Ms. Amann said of the house, which is made from local fieldstone and set amid a rocky outcropping. “It has all these walls, so it looks like some sort of Medieval structure.”

The house still had its original wallpaper when they bought it in 2003, paying $525,000 for the roughly 2,500-square-foot home. The couple loved the home’s original detail, so they made few changes, even keeping the mint-green 1930s bathroom tile.

Then Sandy hit. With the upper portion of the house extensively damaged, they took the opportunity to do a renovation they’d long considered. They hired Manhattan architect Ali C.

Höcek to put an addition on the house, raising the ceiling in an attic to create a sitting room overlooking the lake, among other upgrades.

The challenge, Mr. Höcek said, was making the addition fit with the historic character of the house while balancing the contrasting sensibilities of its occupants, which is reflected in the home’s combination of Arts and Crafts-style stonework and more modern-looking casement windows.

“The steel is Sandra, the stone is Michael,” said Mr. Höcek.

One major hurdle, Mr. Höcek said, was making sure the new stonework would seamlessly blend into the original multicolored granite. The mason found a local quarry with the necessary stone, then paid careful attention to “replicating the way the stones are laid and the size of the mortar,” Mr. Höcek said. To match the home’s original steel casement windows, the team used a combination of reclaimed steel and new steel sourced from Switzerland.

The new addition upstairs has a wall of glass overlooking the lake, and French doors open to a stone terrace. Though the windows look very similar to those in the original portion of the

house, the new room has a decidedly contemporary feel, with black leather chairs, an overhanging steel lamp, and a colorful, three-piece coffee table. Abstract prints by the artist Agnes Martin hang on the wall.

“My taste is way more modern than Michael’s, but I do like the marrying of the two,” said Ms. Amann. Mr. Höcek, she added, “has a way of being sympathetic with what exists while adding something that is perhaps more modern. I think [he does] that particularly nicely.”

Another long deferred-project was gutting a room at front of the house, which wasn’t only “awful” in appearance but turned out to be sinking into the ground, Mr. Höcek said. “It looked like a tiki restaurant,” Ms. Amann said. “A sinking tiki restaurant,” Mr. Höcek added.

They replaced the room’s walls with floor-to-ceiling casement windows so “you get this nice eastern light through the trees,” Mr. Höcek said.

Barely used before Sandy, the room now serves as an office, where Ms. Amann said she likes to retreat when she has reports to write.

But she is especially partial to the room upstairs, where she loves to sit in the morning “and just sort of sequester myself.” With a wine cooler and coffee maker up there, laughed Mr. Pashby, “Sandra hardly ever comes downstairs.”