CLASSICAL PROPORTIONS: With its graceful front portico and classical trim, this house on Mercer Street is a favorite of those who appreciate this style of late 19th century architecture. On November 3, the house will be open as part of the Historical Society of Princeton’s House Tour.

It is the house on Mercer Street that everyone seems to know. With its white pillars and graceful, symmetrical proportions, the mansion at number 200 is stately, yet somehow understated in its elegance. Its recent, two-year transformation, from a bit tired-looking back to its former glory, was closely watched by curious drivers who craned their necks to check on the progress of the renovation.

The turn-of-the-century house, originally the home of Princeton University classics professor John Howell Westcott, is the centerpiece of the Historical Society of Princeton’s House Tour on Saturday, November 3 from 10 a.m. to 4 p.m. Also open for viewing that day are Boxwood Cottage at 100 Quarry Lane, Guernsey Hall at 68 Lovers Lane Number 1, the Joseph Olden House at 130 Stockton Street, and a home at 28 Quarry Street.

Including the Westcott house on the tour was clearly a coup for the Historical Society. “Given the design, scale, and history of the home, as well as the recent renovations, we felt confident the general public would be interested in seeing 200 Mercer,” said Erin Dougherty, executive director. “And thanks to the generosity of the homeowners, they can. We’re grateful to Knight Architects for working with us on the interpretation of the home as well.”

Princeton architect Catherine Knight and venture capitalist John Clarke first began talking about 200 Mercer on the soccer field, where their daughters competed. When Mr. Clarke mentioned to Ms. Knight that he and his wife Melanie, who is the executive director of the Princeton Symphony Orchestra, were thinking of buying the house at 200 Mercer, she agreed to come take a look.

The house was built in 1896-97 and rebuilt to the same style after a fire in 1903. Its last occupant, Douglas Bushnell, died in 2007. Mr. Bushnell had an original letter dated 20 August 1896 from William E. Stone, the architect, to Mr. Westcott, regarding the style of the columns. That letter has been passed on to the current owners. Mr. Bushnell also had original elevations and plans for the main house and the playhouse, which still stands today.

Mr. Bushnell had lived in Hopewell with his wife, Betty Wold Johnson, for several years before his death. He kept the house, using it primarily to store his substantial collection of H.M.S. Titanic memorabilia, according to local lore. Though 200 Mercer was cared for, it needed substantial work.

“I knew the house, of course, since I had driven by so many times,” Ms. Knight said. “It was a beautiful property. But I could see that it would be a huge undertaking.”

On Ms. Knight’s recommendation, an early demolition permit was pulled to allow an in-depth analysis of the existing conditions. From top to bottom, the house cried out for attention. “The basement was wet, but that is typical for a stone foundation,” Ms. Knight said. “We pulled out the old slabs and put in new ones, with water remediation below. A tremendous insulation package went in.”

A chimney reconstruction — there are eight fireplaces — revealed more than 40 tons of material, all of which had to be removed. An elevator was added. Next was the mahogany staircase, which the team attempted to save. “The staircase had failed,” said Ms. Knight. “It turned out there had been a fire in the wall, and it had slipped. We couldn’t save it, which was a big disappointment. But we had a new stair built, and it is sympathetic to the old one.”

Whether the fire that resulted in that water damage was the one in 1903 that caused the owners to rebuild, Ms. Knight isn’t sure. What is curious, she said, is the fact that several of the timbers used showed some evidence of a fire, which could mean they were recycled from the ruins and used to rebuild.

Ms. Knight’s general contractor Tom Pinneo located experts and craftspeople from the central New Jersey area and Bucks County, Pa. to renovate the property. “He found these wonderful people to do work on the chimney, the millwork, to build doors, do the floors,” she said. “He was a huge part of the process. He knew how to find these people and put together a team.”

Ms. Knight and the team worked on the property for a year before actually beginning the 18-month construction process. Once the rebuilding began, the home’s two existing side wings were replaced. One became a sunroom, and the other a sequence of spaces including a mudroom, powder room, and new kitchen. The original kitchen had been in the left front of the house. In the back of the house, an elliptical window, replicating the adjacent covered porch ellipse, was added.

On the second floor, a master bath and two new baths were installed. “I tried to concentrate the new plumbing in one area, also for noise reasons,” Ms. Knight said. “I saved some of the old fixtures, including some tubs and sinks. We used as many doors as we could and as much of the old hardware trim as well. Everything in the house was custom, and we wanted to make it seamless.”

Holly Nelson created the landscape design, which included relocating the playhouse on a new foundation to the rear of the property. “It was amazing that it was in such good shape,” Ms. Knight said. “It was on old stone piers, and there were animals living underneath.”

The playhouse is more of a poolhouse in its present location by the new swimming pool. The old pool, which remained in the ground, is being re-used for a storm water retention system. The project also included construction of a new, three-car garage.

While architects aren’t usually an integral part of the construction process, a historic renovation project of this complexity is different. “We were involved, all the way,” said Ms. Knight, who added many details up until the end of construction. “This was certainly different from a regular renovation project.”

Tickets to the tour are $45 or $40 for members of the Historical Society of Princeton. Visit www.princetonhistory.org or call (609) 921-6748 ext. 105.