On a quiet morning in Historic Odessa, the lawn between the Wilson-Warner House and the Corbit-Sharp House, both built in the late 18th century, looked like a set ready for actors in tri-corner hats and breeches.

A rumble of a classic rock, wafting from an open window in the Wilson-Warner House, broke the spell. A peek into the kitchen revealed a kitchen floor covered with a blue tarp. In a second-floor room, pieces of plaster surrounded a paint bucket, and bricks were exposed below a window.

It was the end of February, and the Historic Odessa Foundation was using the downtime to repair the Georgian-style house for the spring season. Plaster repair, fresh coats of paint and electrical upgrades are business as usual for the Historic Odessa Foundation, which, since 2005, has owned and operated the Historic Houses of Odessa, a collection of 18th- and early 19th-century buildings near the Appoquinimink Creek. But the work is never easy.

“One of the challenges of maintaining historic structures is to ensure that the period of significance of the structure is established, known and adhered to,” said Timothy Slavin, director of Delaware’s Division of Historical and Cultural Affairs. “The Historic Odessa Foundation has painstakingly researched these issues and applied methods and techniques that adhere to national standards for historic preservation.”

Credit H. Rodney Sharp, the original philanthropist behind the Historic Houses of Odessa, for blazing the path. “He did such an extraordinary job when he restored the buildings that it’s the only reason we don’t have more problems,” said Debbie Buckson, executive director of the Historic Odessa Foundation.

Sharp was fascinated by the once-bustling port town, which was originally named Cantwell’s Bridge for the toll bridge across the Appoquinimink Creek. In 1938, he purchased the circa-1774 Corbit House. He then moved the circa-1700 Collins-Sharp House to Odessa.

In 1958, he donated the Corbit-Sharp House to Winterthur Museum & Gardens, which owns and operates a 175-room mansion filled with American decorative arts near Greenville. (Sharp was related to Henry Francis du Pont, the museum’s founder.)

Sharp gave the Collins-Sharp House to Winterthur in 1968, the year he died, and his family donated The Brick Hotel — which opened in 1823 as Cantwell’s Bridge Hotel —to the museum. Winterthur received the Wilson-Warner House in 1969 from the David Wilson Mansion, Inc.

In 2003, facing budget issues, Winterthur shuttered the satellite site. After two years, the property went to the Historic Odessa Foundation.

Today, there are six major structures, including the former First National Bank of Odessa, built in 1855, which was acquired in 2000. It is now the visitors’ center and a banquet space.

The bank isn’t the only example of a thoughtful reuse. During Winterthur’s tenure, the Brick Hotel held the Sewell C. Biggs Collection of Art. Since 2012, it’s been the home of Cantwell’s Tavern, a restaurant.

The tavern recently received the first new roof since H. Rodney Sharp topped the buildings with cement tiles designed to last at least 80 years. The roof now sports real cedar shingles. The roof replacement on the other buildings will follow this summer.

Replacing the cement tile was on the repair list in 2005. But back then, there were more pressing issues for Buckson and Jennifer Cabell, the only two employees. Certainly, Buckson was the right person to prioritize the work. She was the curator of education at Historic Houses of Odessa from 1981 to 1999, and for eight years, she lived in the Collins-Sharp House.

“We looked at the properties with a critical eye,” said Buckson, who hired a historic preservationist to do an assessment. “There had been deferred maintenance issues that Winterthur was struggling to address. They didn’t intentionally allow things to go. It’s just that the funding was extremely difficult to get.”

While ramping up programming and enlisting volunteer guides, she wrote grants for the repairs, which were “enormous,” she said. “We were behind the eight ball.” Foundations were concerned that the new organization had no track record. The determined Buckson raised $500,000 in the first few years.

The list was subject to change. In 2005, the Brick Hotel’s heating and ventilation unit failed. The building’s antiquated halon fire-extinguishing system needed removal, which required expertise.

One day, Buckson flipped a switch in the Corbit-Sharp House, and the room remained dark. The electrician told her, “You’ve got a real problem.” The electrical system was the same one that Sharp had installed. Similarly, The Pump House was in the same condition as it was in Sharp’s day. HVAC improvements opened a Pandora’s Box of asbestos issues.

Even newer systems had problems. The Corbit-Sharp’s over-engineered system created excess humidity. The historic houses hold valuable artifacts, including furniture made by John Janvier Sr., textiles, glassware, china and artwork. They require stable conditions. Paint and wallpaper were peeling.

Buckson checked items off the list. All six of the major buildings now have HVAC systems in prime working order. Many windows have film that protects artifacts from sunlight. Workers tackled plumbing and wiring issues. The most recent work in the Wilson-Warner House includes wiring and plaster repair.

As with any home, the structures require regular painting. The foundation hired experts to analyze the exterior and interior walls and woodwork. It was not the first time the structures had undergone analysis. A door in the Corbit-Sharp House shows a square from which layers of paint were removed to find the original color. But previous analysts lacked the high-powered microscopes that identify pigments, binders and fillers. A recent study determined that the master chamber wall originally had a glaze made with a vibrant verdigris-based pigment.

Catherine Adams Masek, whose mother grew up outside of Odessa, has worked on the exterior paint analysis since 2006. When she started, most of the buildings had exterior white trim, which was particularly popular in the mid-20th century because of durable titanium, said Masek, who is based in Severna Park, Md.

But 18th-century houses would have featured linseed oil-based, hand-mixed finishes with iron oxide that add a cinnamon, ochre or reddish-brown hue. Greens and other natural colors were favored in the mid-19th century as a back-to-nature movement spread throughout Europe and America.

Recreating the original paints would be expensive, unstable and potentially dangerous; paint in the past contained lead. The foundation has found modern-day color equivalents, and the homes boast a significantly changed color scheme than they did before 2005.

To date, the foundation has spent more than $2 million on preservation. Replacing the roofs, which will cost $425,000, is the last of the major projects. The foundation can now follow a regular schedule of maintenance, such as replacing water-damaged wood and repairing the hand-painted Chinese wallpaper in the Corbit-Sharp House.

Although Buckson acknowledged that “anything can go wrong,” she and her team are ready for battle. “Their commitment to ensuring that standards are followed is evidenced by the absolute beauty of their work,” said Slavin of the Division of Historical and Cultural Affairs.

Buckson is proud of the 30-acre complex, and is looking to buy more acreage along the waterfront.

“This has been a long and arduous preservation,” she said. “This site is, I think, at a very high level of maintenance for an 18th-century Colonial site.”