Metamorphosis

• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.
• Photo courtesy of Dunn Roofing and Sheet Metal Inc.

Lorton Correctional Facility Occoquan in Lorton, Va., once was Washington, D.C.'s primary prison and has been a source of debate for years with regard to prison conditions, scandals and its historical buildings, among other issues.

The prison closed in 2001 and now is being transformed into The Workhouse Arts Center. The Lorton Arts Foundation will use the facility for art education, recreation and as a channel for self-expression.

The halls that once held prisoners now will be home to art studios, galleries, performance spaces and recreational facilities, among other new spaces. However, a part of the old buildings was used to help rejuvenate the facility—much of the original slate was salvaged and reinstalled.

Dunn Roofing and Sheet Metal Inc., Manassas, Va., was asked to perform a demanding task—remove 1,700 squares (15300 m²) of original slate; salvage at least 60 percent of the slate; and reroof 15 buildings with the salvaged slate and some new supplemental slate.

Recycling

The prison's original roof system consisted of 1,700 squares (15300 m²) of 3?16- by 16- by 8-inch (5- by 406- by 203-mm) slate, a layer of deteriorating building felt and 1 x 6 tongue-and-groove wood deck. The original slate had been installed sometime between 1910 and 1950.

Twenty-eight workers were involved with the tear-off, which required great care to preserve the original slate.

"The tear-off consisted of a large crew, scaffolding systems and several hydraulic four-wheel-drive, all-terrain forklifts capable of lifting 6,000 pounds (2722 kg)," says Mike Dunn, president of Dunn Roofing and Sheet Metal. "The workers removed the slate from the roof carefully, using pry bars and their gloved hands, and loaded the slate in a bucket attached to the front end of the forklift's extended boom."

The company was able to salvage about 800 squares (7200 m²) of the original slate, which was about 47 percent of the roof, for reinstallation.

"The slate then was transported to the ground for inspection," Dunn says. "After being inspected for quality, the slate was stacked in rows of 100 on the ground and deemed ready for restocking. Keeping the ground clean was challenging because about 1 million nails had been removed from the existing roof."

All workers on the roof were required to wear personal protective equipment; tie off using a D-ring anchor point; and use a 25-foot (8-m) safety rope with rope grab, 6-foot (2-m) shock-absorbing lanyard and full-body harness. Scaffolding also was used for performing work on buildings where the eave was about 35 feet (11 m) high.

Clean slate

Dunn Roofing and Sheet Metal replaced about 360 squares (3240 m²) of wood deck with 1 x 6 No. 1 pine boards and nailed two plies of No. 30 felt material to the wood deck using plastic cap nails. In addition, 40-mil- (0.04-inch- [1-mm-]) thick self-adhering underlayment was applied at all valleys and eaves. All flashings consisted of 16-ounce copper, and all valleys consisted of 16-ounce copper soldered in place.

Installing the slate was a complicated process.

"The salvaged slate and new slate were installed using 1 1/4-inch (32-mm) copper slating nails that would not penetrate the underside of the roof deck," Dunn says. "The original nails removed from the roof were 1 1/4-inch (32-mm) copper and still in great shape after about 80 years. The slate was installed using a 4-inch (102-mm) headlap and two nails per piece of slate. About 500,000 pieces of slate were installed using more than 1 million nails. Virginia Slate Co., Richmond, Va., supplied about 900 squares (8100 m²) of new slate to supplement the salvaged slate."

The project involved eight material handlers and 29 slate installers, which caused some concern.

"With the amount of people we used to install slate, we were concerned our supply would deplete and slate availability would become an issue," Dunn says. "Slate was supplied as it was produced. When 29 slate installers are on your job site, you certainly need material to keep them busy or they may decide to move on to other projects.

"However, Virginia Slate supplied the project with high-quality imported slate. The slate was packed tightly in well-built crates, was intact and rung out nicely when tapped with a hammer. We were impressed with Virginia Slate's ability to supply the 900 squares (8100 m²) needed to keep the job rolling."

Workers needed

Finding an adequate number of workers was one of the most notable challenges of this large-scale project.

"The greatest challenge we faced was finding the manpower required to undertake such a huge and time-consuming task and also provide the quality that a beautiful slate roof is known to possess," Dunn says. "We started the tear-off phase with company employees, but we have only seven employees who are knowledgeable about slate installation. Seven installers could not finish 1,700 squares (15300 m²) in six months.

"As we progressed, we recognized the need for slate installers," he continues. "We were three weeks behind schedule with the slate installation, so we called some friends in the roofing business and were lucky enough to round up the assistance of two local companies experienced with slate—Gueriera Roofing Inc., Manassas, Va., and Wyant Contractors, Burke, Va. With help from these companies, we were able to allocate enough manpower for installing slate to meet the demands of the schedule."

Dunn says the project was unique because of its size and difficulty, tight schedule, and one of the buildings presented the company with a lightweight concrete plank roof deck.

"The construction manager did not want to install the slate directly to the concrete," Dunn says. "An asbestos tile previously was nailed to the concrete with common nails, and you wouldn't nail into hard nailable concrete with copper nails. Using common nails was out of the question. Instead, we agreed to install a wood deck system over the concrete."

The wood deck consisted of five-quarter by 6-inch (32- by 152-mm) pressure-treated lumber nailed and glued to the concrete deck so it was parallel to the roof slope and spaced 16 inches (406 mm) on center. The company then glued five-ply structural-grade 3/4-inch- (19-mm-) thick plywood to the pressure-treated lumber sleepers and anchored the sleeper and plywood to the concrete.

"A structural engineer checked the system design before the work began to ensure all components were designed to handle the weight of the slate roof and pass code," Dunn says. "The five-quarter-thick lumber created the 1-inch (25-mm) air space for venting. We installed a vented ridge system consisting of a copper cap cleated to perforated stainless steel."

A team effort

Dunn appreciates the collaborative effort of those involved, especially when performing work on a demanding, large-scale project during a six-month period.

"The most rewarding part of the job was watching everyone involved work as a team to accomplish the goal and finishing the project with a well-satisfied customer," Dunn says. "And we finished on time. It was an amazing feat."

Krista Reisdorf is managing editor of Professional Roofing magazine.

Project name: Lorton Correctional Facility Occoquan
Project location: Lorton, Va.
Project duration: June 2005-February 2006
Roof system type: Slate roof system
Roofing contractor: Dunn Roofing and Sheet Metal Inc., Manassas, Va.
Roofing manufacturer: Virginia Slate Co., Richmond, Va.