Home to George Mason, author of the Virginia Declaration of Rights and a founding father and signatory to the U.S. Declaration of Independence, Gunston Hall is a Georgian mansion near the Potomac River in Mason Neck, Va. Constructed in the middle of a 550-acre tobacco and wheat plantation between 1755 and 1759, the architectural treasure is not far from Mount Vernon, where George Washington once resided.
Few changes have been made to the mansion since its completion in 1759, making it a vital example of an architectural moment in colonial Virginia. Designed and constructed by William Bernard and William Buckland, the mansion's eclectic interiors illustrate the 18th century's Rococo style—a central passageway incorporates French Modern and Neoclassical elements; a porch reflects Gothic style; one room is designed in a "Chinese Taste"; and a doorway and cornice are embellished with Palladianism elements. The two men also produced furniture for the "Chinese Room," a rare feature at the time.
In 1949, the mansion was gifted to the Commonwealth of Virginia to be administered by the Board of Regents of The National Society of The Colonial Dames of America. Now a museum accredited by the American Association of Museums, Gunston Hall is open to the public and features exhibits, a visitors' center and museum shop.
During 2014-15, Gunston Hall's 4,500-square-foot slate roof systems were renovated to original cedar shakes specifications by Ruff Roofers Inc., Baltimore.
Tear-off
Gunston Hall has a gable roof with ten dormers and four chimneys. There is a transition area about 3 feet from the eaves where the roof slope changes from 4:12 to 9:12. The building has two entries on the main level—one has a gable roof, and the other has a hipped roof. There also are two cellar entries—both with gable roofs. Originally, the main roof was covered with cedar shakes, but it had been replaced with slate while under private ownership. Ruff Roofers' challenge was to restore all the roof systems to the original cedar shakes design.
Workers began the tear-off process in December 2014 by removing the existing 5/8-inch-thick Buckingham® slate and two-ply asphalt felt underlayment down to the wood plank roof deck. During the demolition phase, deteriorated wood was discovered.
Workers laid new felt underlayment as a temporary waterproofing measure while replacing damaged planks with 5/4-inch boards in random widths to match the dimensions of the existing wood. Although all exposed sheathing was covered with new underlayment following demolition, workers covered the roof with tarp every day during this process as an added precaution to ensure the building remained dry.
Portions of the original deck with the original nails intact were salvaged to keep as artifacts of the mansion's original construction methods. These pieces now are on display in Gunston Hall's museum.
In addition, deteriorated chimney bricks were repaired to historical standards, matching the mortar mix circa 1750s. In some areas around the eaves, the crown molding was rotted. Ruff Roofers produced a custom profile to match the existing molding to repair it.
Following repairs, workers applied VaproShield® and Benjamin Obdyke Cedar Breather® underlayments.
New cedar shakes
To restore the original roof design details, the architects prepared specifications to replicate the exact dimensions of the original shakes, which no longer are common sizes. The specified shakes species was Alaskan Yellow Cedar 18-inch Tapersawn shakes with a 3/4-inch butt thickness and 100 percent edge grain. This wood species is found in the Pacific Northwest and Alaska and is a hard wood, making fabrication of the 3/4-inch butt more difficult as cedar typically is produced with a 5/8-inch butt.
Additionally, the 18-inch-long lengths typically are installed with a 7 1/2-inch exposure, but the original roof used a 5 1/2-inch exposure in the field and a 4-inch exposure at the sweep near the eave. The widths of the shakes only could range from 3 1/2 to 5 1/2 inches, a much tighter band of widths than currently produced. Additionally, all the shakes were to have rounded corners.
Once the shakes were produced, each shake was hand-cut to the 1 1/2-inch specified radius. To achieve the desired aesthetic, Ruff Roofers craftsmen cut 30,000 pieces of Alaskan Yellow Cedar, translating to more than 60,000 individual cuts.
Specifications also required a tight 1/16- to 1/8-inch gap between each shake. Workers used wood strips as spacers to maintain a consistent, compliant gap. Current standards call for this shake type to be gapped between 3/8 and 5/8 of an inch, allowing a 1/4-inch variance as opposed to the 1/6-inch variance for the Gunston Hall installation. The narrow gap and tolerance required great care to maintain shake alignment during installation because the force of the nailer could cause a shake to slip or slide as it was being nailed.
As the Ruff Roofers team worked its way up from the eave on the main roof's plane, the plans called for the exposure to change from 5 1/2 inches to 4 inches in the slope transition and return to 5 1/2 inches once above the transition. Although this area had been revised and approved on the mockup, Ruff Roofers questioned the condition.
"We had concerns where shakes were bridging," says Matt Higgins, project manager for Ruff Roofers. "Because the shakes were so hard, we feared they may split or crack under foot traffic. We also were concerned about wind-driven rain migrating through the voids in the rakes, so we recommended wood cants be installed to provide stability for the shakes and to close the voids at the rakes. To maintain a smooth sweep, the cants were cut on-site to fit snugly in the voids. The shakes were carefully laid out, and lengths were adjusted to accommodate the cants."
Challenging details
Once past the sweep, workers moved to the dormers and chimneys. Before beginning shake installation, Ruff Roofers constructed a full-size mockup of the dormers, transition and hip conditions in its warehouse so the team could review critical details with the architect. Much time was required to review the numerous details and make adjustments to the actual field conditions.
The dormer sills' original construction presented a waterproofing challenge. The details required lead flashing set below the sills and masonry chimneys to act as a seal. However, the existing blocking would not accommodate this detail, so workers custom-fit new blocking to allow the sill flashing to be properly installed to shed water. The dormers weren't as user-friendly as the chimneys because the wood provided too much "bounce." However, workers took their time and carefully packed the lead into place and achieved the necessary and desired finish.
As work progressed, workers precisely cut the dormers' existing siding's bottom board to match the shakes' profile, maintaining a uniform gap throughout every dormer.
At the top of the dormers, workers needed to sweep the valleys between the main roof plane and the dormers' roofs. The team adjusted the coursing of the roof planes to blend with the valleys, a difficult task despite successfully completing the mockup detail. As a result of settlement over time, the dormers were out of square with the main roof's plane. This meant each valley had to be laid out differently to preserve a uniform look.
"Working on a 200-year-old building that generally was out of square had its challenges from an aesthetic perspective," Higgins says. "We overcame some of these issues by creating a full-size mockup. Alaskan Yellow Cedar is quite dense, which makes it difficult to coordinate transitions and angle changes around the roof. Many of these transitions were dry-laid in place first and then installed in painstaking detail to ensure the shakes were properly laid and aligned with dormers, valleys and hips."
Similar to the dormer valleys, the rear portico had a hipped roof that also required sweeping of the shakes within proximity of the hip and careful beveling of hip corners. Ruff Roofers prepared a carefully crafted in situ mockup of the exact field conditions and disassembled the mockup, labelling each piece on each course on the left and right sides so workers could fabricate complete hip packages in Ruff Roofers' shop to ensure precision cutting. The 24-inch shakes were used to facilitate sweeps at the hips.
In addition, lightning protection was added to protect the structure from storm damage. Careful planning and routing of the system was required to reach the performance requirements without disturbing historical interior finishes. The Board of Regents wanted to minimize the appearance of the new lightning system, so all the cables below the roof line were run through the interior.
Because exothermic welding was necessary to bond the conductors to the new ground rods, careful coordination was necessary between the alarm company, fire suppression company, lightning protection subcontractor and Board of Regents. Ruff Roofers was instrumental with coordinating the sequence and execution of the many tasks necessary to complete the work without incident.
Safety
Gunston Hall remained open to the public during the entire roof system replacement project. Field trips of about 200 elementary schoolchildren toured the building and grounds almost daily. Ruff Roofers ensured the safety of pedestrians by installing overhead protection at all entryways, as well as temporary construction fencing. The Ruff Roofers crew remained diligent about protecting the public during the entire reroofing project.
To secure worker safety, Ruff Roofers placed scaffolding around the entire building just below the eave and required the team to be tied off with ridge anchors, ropes and harnesses when necessary.
"By implementing strict safety precautions, we created and maintained an accident-free site," Higgins says. "All work was completed without incident."
Back to the past
After six months of rigorous planning and merciless attention to detail, Ruff Roofers completed its work on Gunston Hall in June 2015.
"The result of Ruff Roofers' efforts and professionalism resulted in a rare historical dwelling being returned to its original state for many visitors to enjoy for decades to come," says Scott Muir Stroh III, executive director for Gunston Hall.
For demonstrating exceptional workmanship on Gunston Hall, Ruff Roofers was selected as a 2016 Gold Circle Awards finalist in the Outstanding Workmanship: Steep-slope category.
"It was our privilege to work on the home of George Mason, co-founding father and signer of the Declaration of Independence," Higgins says. "The project required extensive preparation, rock-solid safety procedures and vigorous attention to detail to protect a historical and national landmark. To contribute to a moment in history was remarkable, especially reconstructing roof systems that were installed by craftsmen in 1755."
Chrystine Elle Hanus is Professional Roofing's associate editor and NRCA's director of communications.
Project name: Gunston Hall
Project location: Mason Neck, Va.
Project duration: December 2014-June 2015
Roof system type: Cedar shakes
Roofing contractor: Ruff Roofers Inc., Baltimore
Roofing manufacturers: Benjamin Obdyke Inc., Horsham, Pa.; VaproShield® USA, Gig Harbor, Wash.; Waldun Group,
Sumas, Wash.
Gold Circle Awards category: Outstanding Workmanship: Steep-slope
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