Norwich — It’s the offseason for the Leffingwell House Museum, but this winter won’t be the typical slow period for the caretakers of the circa 1675 historic house, as they embark on an urgent $40,000 fundraising drive to replace the cedar shake roof after leaks were discovered in the fall.

Dayne Rugh, president of the volunteer board of directors for the Society of the Founders, which owns the museum, said Wednesday a rear portion of the roof — not visible from the main façade or Washington or Town streets — was covered by a black tarp to prevent further damage from water seeping into the building.

The entire cedar shake roof last was replaced about 35 years ago, Rugh said, and needs to be replaced again.

In fall, the society brought in professional collections assessors to evaluate the site and the museum’s extensive collection of artifacts and antiques. The group went beyond the collection itself to inspect the building’s condition.

That’s when it was revealed that the northern portion of the building's roof was covered with a thinner grade of cedar shakes. That portion now is failing, and moisture had seeped into the hallway and damaged the plaster, Rugh said.

Rugh said the problem was discovered early and no major leaks or water damage has occurred. The black tarp, secured to the rear roof and around one of the chimneys, has stopped the leaks.

The Society of the Founders launched a “raise the roof” fund drive in early December to raise the $40,000 needed to replace the entire roof this year. Replacing just the weaker northern portion was estimated at $15,000, but Rugh said it wouldn’t make sense to replace a portion of the roof now, only to come back in a few years to replace the rest.

“We dearly would like to have it done this year,” he said. “The time is ticking. If we can get it done this calendar year, that would be tremendous.”

The new roof must be cedar shake shingles to retain the house’s historical integrity, Rugh said.

The fund drive has raised about $8,000 thus far through individual donations. The first of a series of fundraisers for the roof project will be held Jan. 26 at Illiano’s Grill Restaurant at 257 W. Town St. During the restaurant’s hours, from 11 a.m. to 9:30 p.m. that day, 15 percent of customers’ checks will be donated to the Leffingwell roof drive.

Additional fundraisers will be planned in the months ahead. People can donate to the museum through its website, leffingwellhousemuseum.org or send checks made out to Leffingwell House Museum to P.O. Box 62, Norwich, CT 06360. The society will pursue grants, as well, Rugh said.

The roof fund drive is just the first of several planned capital campaigns for the museum as it gears up for its 350th anniversary in 2025. The house is in “remarkably good shape for its age,” Rugh said, but there are plenty of capital upgrades that could be done, including expansion of the parking lot, improvements to facilities inside and redoing the basement restrooms.

The society also owns the circa 1760 David Greenleaf House next door. The society received a $4,000 grant last summer from The Last Green Valley National Heritage Corridor and additional funding through the Neighborhood Assistance Program to stabilize and restore the rear of the house. The building now is used for storage.

“The ultimate goal is to make the property usable and accessible,” Rugh said.

c.bessette@theday.com