After restorations that have taken more than six months, Montpelier Mansion has thrown open its doors to visitors once again.

But don't look for a new look — or even a facelift on the 18th-century Georgian beauty.

Almost all the restoration work took place behind the scenes, in the cellars and crawl spaces.

The result is designed to keep the historic landmark looking its best for another couple of centuries, according to Don Graham, Montpelier's assistant facilities manager.

Regular visitors may notice a few changes: Overgrown boxwoods near the front and river-side entrances have been removed; two terraces built on either end of the mansion in the mid-1900s are gone; and the summer house has been refreshed (and repaired) and is a little more visible now that a couple of overgrown cedars and lilac bushes were cut down, making it more prominent in the landscape as was intended originally, according to Graham. 

But, Graham said, most of the work should be invisible to the average guest.

That's not to say the work wasn't important. Problems with humidity and water in the basement caused the museum house staff to seek a contractor for the $750,000 project in the first place. In the rainy season, a thin layer of water would collect in the basement. The humidity was too high for the collection's antiques and drainpipes weren't draining water away from the house. Even the plantings were too close to the foundation, "a no-no for historic houses," Graham said.

The work was necessary to preserve the house, which was built by Maj. Thomas Snowden and his wife, Anne Snowden, in the mid 1780s. The Prince George's County Department of Parks and Recreation has owned Montpelier since 1961, and the house last underwent restoration in 1983, according to Graham.

Moisture issues top list

Contractor Oak Grove Restorations, of Laytonsville, signed on six months before work began to find solutions to the problems plaguing Montpelier.

Oak Grove has specialized in this historical work for 40 years, according to Hank Handler, vice president of the company he founded. Other current projects for Oak Grove are the Hammond Harwood House in Annapolis and the ruins of Francis Lightfoot Lee's Menokin in Virginia. The company is also repairing earthquake damage at the Sherman Building adjacent to Lincoln's Cottage in Washington, D.C.

Since March, teams of archaeologists, masons, plasterers, carpenters and gardeners worked as many as six days a week. The to-do list was quite long, and moisture issues topped the list.

Even though the house sits on the crest of a hill, the area's high water table caused water to seep into the cellar. So trenches were cut into the cellar's concrete floors, which were added in the mid-20th century to help eliminate flooding and improve air circulation. Eroded mortar and bricks were replaced with historically correct materials.

New trenches were dug — all by hand —around the foundation's exterior. Then, Handler explained, they came up with a way to avoid the usual invasive restoration: they waterproofed a layer of dirt around the foundation rather than exposing the old fragile foundation for waterproofing. And then they added eight sump pumps where there used to be only one, using holes already in the basements.

"We did this without removing a single brick or a single stone from the building," Handler said, adding, "Montpelier is in a class by itself." 

Broken and clogged terra cotta pipes attached to the old downspouts were replaced with PVC — not historical, but practical, according to Graham. "Sometimes you have to go with the better, modern materials," he said.

Two terraces added to either end of the house in the 1930s were also removed. They were in poor condition and didn't match the original design of the house, according to Graham.

As the terraces were removed, landings for steps were uncovered that Graham said were probably built around the time of the Civil War. One outstanding bit of work is to cover them with wooden steps for protection, he said.

There was also time and money for a few cosmetic repairs as well. Old window sashes were stripped of paint and repaired; bookcases in the library were reattached to the walls; and cracked plaster, wainscoting and paneling was painstakingly restored. And outdoors, an existing brick patio was relaid after even more drainage work, and rotted pergola columns were replaced with rot-resistant cypress.

The south chimney, damaged in the 2011 earthquake, was stabilized and bird guards were installed to discourage the turkey buzzards who used to perch there.