North Carolina Legislative Building Restoration Poses Unique Challenges

The North Carolina State Legislative Building was the site of a renovation project that included asbestos abatement in the interior and a complete restoration of the building’s roof systems.

The North Carolina State Legislative Building was the site of a renovation project that included asbestos abatement in the interior and a complete restoration of the building’s roof systems. Photos: SkySite Images

Some of the variables that can make a project difficult include a variety of complex, interconnected systems, unique design elements, and a tight schedule. These challenges are heightened on a highly visible, historic building, where the goal of keeping the design historically accurate must be balanced with making improvements to the structure and functionality of the systems. All of these elements and more were in play during the restoration of the one-of-a-kind roof on the North Carolina State Legislative Building in Raleigh, North Carolina. It took a talented team of design, engineering, and roofing professionals to bring the project to a successful conclusion.

Originally designed by architect Edward Durell Stone, the building has been the home of the state legislature since 1963, but water intrusion under its copper pyramids and at windows and doors on the promenade level precipitated a complete restoration project. Renovation work conducted in 2016 and 2017 included asbestos abatement in the interior and a complete restoration of the building’s roof systems.

The roofing phase of the project included removing and replacing the metal roof systems on the five copper-clad pyramids, as well as re-roofing the low-slope sections adjacent to the pyramids with a two-ply modified bitumen system. A liquid-applied waterproofing system was installed in the planter areas and under the pavers in the promenade section. The project also involved the removal and replacement of windows, doors, and skylights, as well as repairing and coating the concrete surfaces at the perimeter of the roof.

The design of the quilted flat lock copper panel system involved 17 different panel profiles. A false batten was added after the panels were in place.

The design of the quilted flat lock copper panel system involved 17 different panel profiles. A false batten was added after the panels were in place. Photos: SkySite Images

Companies involved in the project included Raymond Engineering, headquartered in Raleigh, North Carolina, which provided engineering and architectural services; Owens Roofing Inc., also located in Raleigh, which served as the general contractor on the roofing phase of the project and installed the low-slope systems; and The Century Slate Company, headquartered in Durham, North Carolina, which removed and replaced the copper roofs on the five pyramids.

Some of the key players in the project shared their insights with Roofing, including John Willers, a senior engineer with Raymond Engineering; Bert Owens, president of Owens Roofing; and Mike Tenoever, president of Century Slate.

“This is an iconic state building with a unique roof system which the owner and designer required to be aesthetically replicated,” Tenoever notes. “At the same time, some functionality and technical improvements were incorporated. This is a very high-profile project with a lot of complexity, particularly given the schedule. There were a lot of details compressed into a very short period of time.”

Design and Pre-Construction

Raymond Engineering conducted testing on the existing roofs and specified systems designed to match the originals and provide some necessary improvements, including added insulation and ventilation under the pyramids. Willers worked closely with Jason Mobraten, the senior architect on the project. “We provided the engineering and architectural services, beginning with design and then assisting with bidding and managing the construction phase of this project,” says Willers. “We engineered the copper roof, all of the detailing for the modified asphalt roof, and the detailing for the drainage, the pavers, and the sealants for the promenade.”

Crews from Owens Roofing removed the existing plants, media and drainage system from four 42-foot-by-42-foot fixed planters with skylights. After the substrate was cleaned and primed, a liquid-applied waterproofing system was installed.

Crews from Owens Roofing removed the existing plants, media and drainage system from four 42-foot-by-42-foot fixed planters with skylights. After the substrate was cleaned and primed, a liquid-applied waterproofing system was installed. Photos: SkySite Images

The schedule was an obvious challenge, as the majority of the work had to be completed while the legislature was in recess, and there were substantial financial penalties that would come into play if the work was not completed on time. “The client also required that the asbestos abatement be completed before re-roofing the copper-clad pyramids to avoid the risk of dislodging the asbestos-containing textured ceiling finish. However, doing the work in two phases allowed the asbestos contractor to get started while the rest of the job was designed and bid,” Willers states.

The building houses legislators’ offices, and it was open and occupied during construction, with the exception of the areas undergoing asbestos abatement. The schedule had to be carefully adjusted as the job progressed. “In addition to our role in monitoring the technical aspects of the construction, we closely monitored the construction phasing and sequencing, as it was directly driven by the schedule of the state legislature,” Willers notes. “We had to take a lot of care in developing the schedule and monitoring it.”

Willers and Mobraten knew that the details on this project would be crucial. “There were previously some issues where the copper and the low-slope membrane roofs met,” Willers says. “We detailed that very carefully so that we had redundancy in keeping that watertight.”

Extensive mock-ups of the copper pyramids were constructed and tested to ensure the quilted pattern could be exactly replicated while avoiding the leaks that plagued the existing structure.

Photos: SkySite Images

Photos: SkySite Images

As designers looked for ways to improve construction, they explored the design and construction of the quilted panels. “From a design standpoint, we wondered why we had this odd diamond-shaped pattern,” Willers recalls. “After we played with the dimensions a bit, we realized that if you fly over the building, from above all of those diamond sections look like squares.”

The key was to replicate the design with its false battens while avoiding leaks. “We were concerned about how to detail out the joining of the copper sheets that formed the diamond-shaped panels,” Willers says. “What had been done was susceptible to windblown rain getting in. We did two things differently: the little clips that supported these battens were secured by forming the clips with hooks that would be integral with the single-locked seams and soldering the clips to the top surface of the copper panels. Previously they were held in place by pop rivets, which went through the copper.”

The Secrets of the Pyramids

Century Slate was well prepared to tackle the copper roofing on the project. The company has been in business more than 20 years, and it specializes in historic restoration projects including slate, tile, wood, copper and other historical metals.

Crews from Century Slate removed the existing copper panels. The copper was salvaged and recycled.

Crews from Century Slate removed the existing copper panels. The copper was salvaged and recycled. Photos: SkySite Images

Tenoever knew the design of the original quilted flat lock copper panel system needed to be replicated exactly. “There were 17 different panel profiles, each within a very particular location within the roof’s quilted pattern,” Tenoever notes. “Proper placement of each different profile was essential to the whole system working correctly and looking like the original.”

The first step was to remove the existing copper roofs. “We tore off the entire system down to the deck,” Tenoever explains. “We then installed a semi permeable a vapor barrier, insulation, and a vapor retarder.”

Along with added insulation and Carlisle WIP 300HT self-adhering underlayment, crews also installed a vented nail base from Hunter Panels. “The Hunter Cool-Vent is a vented nail base that gets screwed down,” Tenoever says. “The goal was to have a breathable air cavity. All of the hip caps are actually vented to allow the air to get out.”

With the addition of the insulation and nail base, the roof was built up approximately 6 inches from the previous configuration. This added height necessitated changes in the custom flashing at the base of the pyramids but did not change the configuration of the copper panels.

In all, 22,500 square feet of copper panels fabricated by K&M Sheet Metal in Durham were installed. Each of the 17 different panels was labeled with a letter code. “When they were out at the site, we could just grab an A panel or a B panel, as needed, and bring them to that layout,” Tenoever explains. “Four of the pyramids were the same, and the center one was different, as that was the one that had skylights built into it.”

The areas between the pyramids were covered with a two-ply modified bitumen roofing system. Photos: SkySite Images

The panels feature flat-lock clips that were screwed down to the nail base. “It’s a typical flat seam panel system, and the panels interlock together,” says Tenoever. “You can see the batten panel above it, which is an aesthetic feature. The battens and the clips that held them were amazingly intricate, for what they were. They were cut out with a CNC machine and soldered onto the copper panels prior to installation. Later we came back and installed the batten system over the top.”

Century Slate built new curbs in the center pyramid for the new skylights, which were manufactured by Wasco. “The skylights were one of the last things to go on,” says Tenoever. “They were custom made because even though they look square, there isn’t a square angle on them.”

Custom copper flashings were installed at the bases. “One of the trickier parts for us probably would have been the tie-in of the modified roof, because Owens Roofing had to do their bit, and we were also replacing all of the wood blocking and everything all along the bottom edge before we could put our flashing on,” Tenoever recalls. “It took a lot of coordination between the two trades, but it all worked out.”

The Low-Slope Roof Systems

Owens Roofing served as the general contractor on the project and installed the low-slope roof systems. The company was established in 1986 in Raleigh, and focuses on commercial and institutional buildings, almost exclusively re-roofing. Much of its work is on historic buildings, so Owens was confident he could execute the project and complete it on schedule.

A scaffolding system offered secure roof access, but material had to be loaded and removed from one access point, so logistics had to be carefully mapped out.

A scaffolding system offered secure roof access, but material had to be loaded and removed from one access point, so logistics had to be carefully mapped out. Photos: SkySite Images

Crews from Owens Roofing installed 18,900 square feet of modified bitumen roofing from Soprema over concrete decks, including the areas between the pyramids. Tapered polyiso and half-inch DEXcell cover board from National Gypsum were installed using Duotack adhesive, followed by the two plies of modified bitumen membrane.

A liquid waterproofing system from Sika was specified for the large planter areas. Crews from Owens Roofing removed the existing plants, media and drainage system from four 42-foot-by-42-foot fixed planters with skylights. After the substrate had been cleaned and primed, the Sika RoofPro system was installed.

“Once it’s cleaned and primed, it’s pretty simple,” says Owens. “The product is one part, and you don’t even have to mix it. We applied it with rollers on this project. You embed fabric sheets in the system and then topcoat it. It was a cold-weather job, but fortunately we caught a break last winter in that it wasn’t as cold as usual, and we didn’t miss as much time as we might have.”

The 30,000-square-foot promenade section was originally covered by white granite pavers native to North Carolina. The old pavers were removed and replaced over a new roof system, which was comprised of modified bitumen sheets beneath the liquid-applied waterproofing system. “The concrete deck was primed and a modified bitumen base ply heat welded to the deck,” Owens explains. “This surface was primed in preparation for the Roof Pro system, which was then installed.”

Innovative Roof Services of Raleigh was called in to conduct a high-voltage electrical testing to ensure there were no voids in the system before the pavers were re-installed. The pavers had originally been set in a bed of mortar, and they had to be removed and cleaned, which revealed a problem. “When we took the pavers up, we found out that they ranged between 1-1/8 and 1-3/4 inches thick,” Owens notes. “That wasn’t a problem when they were set in a bed of mortar, but over extruded polystyrene, they would have been all up and down. We put in a change order and had the pavers set in a bed of sand on top of one layer polystyrene.” The sand was adjusted by hand to ensure the pavers were level. New pavers were added to replace those broken over the years.

On the roof’s concrete eyebrows, damaged areas of concrete were repaired, joints were sealed, and a cold-applied waterproofing system from Sika Sarnafil was used to cover 8,800 square feet of concrete.

Numerous Challenges

Important considerations on the project included safety and logistics, as well as the tight schedule. Safety was paramount, and a third-party safety monitor was on the site to ensure the safety plan was designed and executed properly. During the time between when the original skylights were removed and when their replacements installed, the voids in the roof deck needed to be cordoned off and covered according to OSHA regulations. Personal fall arrest systems were used on the pyramids and outside of the safety perimeter, which was marked with flags. “With the promenade, you had a wide concrete eyebrow, so it made it easier to set up the safety lines and keep everyone safely away from the edge,” Owens notes.

This aerial photo taken before the restoration project shows the copper roofs with their green patina. Photos: SkySite Images

“Safety is a key concern as on all jobs, but this one in particular was highly visible out the windows of the nearby Department of Labor,” Owens continues. “We were paid a courtesy visit and agreed with them that an on-site safety meeting conducted by their personnel might be useful. The owner allowed us use of one of their auditoriums and we had a very productive half-day meeting for all trades. Every week we had a meeting with a state construction monitor.”

A scaffolding system was set up that offered secure roof access, but there was only one point for loading and unloading material, so logistics at the site were a concern. “We had to use wheelbarrows and roof carts to transport materials back and forth to the scaffolding tower,” Tenoever notes. “Between the removal of the original roof and the installation of the multiple layers of the new roof system, over 150,000 square feet of roofing materials were moved by hand over an average distance of approximately 200 feet.”

Loading and unloading added another wrinkle to the complicated schedule. “The schedule was based on when the legislature was scheduled to come back to town—not how long the job was supposed to take,” Owens says. “We were all concerned with the ambitious time frame and $1,000 a day liquidated damages included with this job.”

Willers cited excellent communication as one of the keys to completing the project on time. “Fortunately, the project managers for the general contractor and other trades were highly organized individuals,” Willers says. “Regular site meetings were detailed and thorough. Although setbacks did occur, communication kept the ball rolling.”

The roof system on the building’s iconic copper clad pyramids was removed and carefully recreated, matching the original design while adding a vented cavity and increasing the thermal insulation. Photos: SkySite Images

A Unique Experience

Copper removed from the existing roof was salvaged and recycled, notes Willers, with the exception of a few pieces that

were cut into the shape of the state of North Carolina to serve as mementos of the unique project. “We’re very proud of the design and the outcome—and the assistance we got from all of the contractors involved,” Willers says. “We had some pretty heavy rains after the project was completed, including some high winds, and there were no leaks.”

Tenoever also looks back on the project with pride. “A one-of-a-kind roof system was custom built and delivered on schedule and with the owner and designer’s praises,” he says. “Taking something so amazing and restoring it to the beauty it originally had—we all get a kick out of that.”

TEAM

Design and Engineering Services: Raymond Engineering, Raleigh, North Carolina, RaymondLLC.com
General Contractor: Owens Roofing Inc., Raleigh, North Carolina
Metal Roofing Contractor: The Century Slate Company, Durham, North Carolina, CenturySlate.com
Leak Testing: Innovative Roof Services, LLC, Raleigh, North Carolina, IRS-LLC.net

MATERIALS

Metal Roof System
Copper: 20-ounce copper sheet metal
Vented Nail Base: Hunter Cool-Vent, Hunter Panels, HunterPanels.com
Underlayment: Carlisle WIP 300HT, Carlisle, Carlislewipproducts.com
Skylights: Wasco Skylights, Wascoskylights.com

Modified Bitumen Membrane Roof System

Membrane: Sopralene Flam 180 and Sopralene Flam 180 FR GR, Soprema, Soprema.us
Adhesive: Duotack, Soprema
Insulation: Sopra-Iso, Soprema
Cover Board: DEXcell, National Gypsum, NationalGypsum.com

Waterproofing System

Liquid Applied Membrane: RoofPro 641, Sika Corp., USA.Sika.com
Reinforcing Fabric: Reemat, Sika Corp.
Primer: Sikalastic EP Primer/Sealer
Extruded Polystyrene Insulation: Foamular 604, Owens Corning, OwensCorning.com

Roofing Companies Form Asphalt Underlayment Council

Four roofing companies—Carlisle, Gardner-Gibson, Maryland Paper and Mid-States Asphalt—have formed the Asphalt Underlayment Council (AUC), a new industry association developed to cultivate the long-term success of underlayment products for building envelope applications for both residential and commercial structures.

This new group’s Interim Executive Council was instrumental in identifying the need for an industry council that supports the standardization of underlayment product quality, performance and integrity. Current AUC members include Owens Corning, Polyglass USA, Mule-Hide Manufacturing, GMC Roofing & Building Paper, GAP Roofing, Warrior Roofing Manufacturing and GAF

“With the introduction of new types of roofing underlayment products, it was felt that an industry group was needed to monitor, administer and contribute to product standards,” noted AUC Executive Director Michelle Miller.

Because standards and requirements for roof repair, reroofing, roof recovering and replacement often lack clarification within the definition of underlayment, AUC’s inaugural technical committee will focus on code classifications and industry regulations.

“The pathways to code compliance vary depending on the product type,” said John Woestman, AUC’s technical director. “The continuous influx of newly designed products and ever-evolving regulations requires a strong knowledge base with deep understanding of the codes prevalent in this industry.”

Bringing regulatory issues to light through educational initiatives and industry outreach will be accomplished through raising awareness and advocacy. AUC will actively assist in the development of building codes to ensure the high performance of roofing systems in the future.

“We will work directly with installers and contractors who may not be aware of the various product categories that are occurring in the underlayment industry,” said Robert Almon, AUC Interim Executive Council member. “Understanding the nuances of underlayment as well as discerning codes and comprehending code compliance are vital. With our combined historical experience, AUC is in a prime position to ensure all the issues surrounding underlayment are addressed through a range of resources from an engaged council, committees and membership to a vibrant website that will be launched soon, growing media outreach, literature development and ongoing educational opportunities.”

The group welcomes roofing underlayment firms to join AUC to work to make these important initiatives viable and sustainable. To learn more about the Asphalt Underlayment Council or to ask about membership, email info@aucunderlaymentcouncil.org or call (847) 686-2243.

Carlisle Acquires Drexel Metals

Carlisle Companies Inc. announced the acquisition of Drexel Metals Inc., a provider of architectural standing seam metal roofing systems for commercial, institutional and residential applications.
With annual sales of approximately $50 million and 65 employees, Drexel Metals is headquartered in Louisville, Ky., and has facilities in Maryland, Pa., Colorado and Florida from which it serves more than 700 customers. Drexel designs and fabricates metal roofing systems for both residential and non-residential applications. Drexel both fabricates its products in its facilities and offers distributors and installers a field fabrication program backed by the company’s premium brand, marketing support, training, testing and warranties.
The business will operate as a unit within Carlisle Construction Materials (CCM), a manufacturer of a complete range of roofing and waterproofing products for commercial and industrial buildings, including single-ply roofing, rigid foam insulations, below-grade waterproofing and air/vapor barrier systems.
“Drexel Metals provides Carlisle Construction Materials a complementary addition to its range of roofing products and systems as well as access to new end markets and sales channels, said D. Christian “Chris” Koch, Carlisle’s president and chief executive officer. “Drexel provides an excellent foundation for additional growth investment in a growing roofing products sector. This acquisition is consistent with CCM’s strategy of expanding into premium products for the building envelope in attractive growth sectors. We are very pleased to welcome the Drexel Metals team to Carlisle.”

Choose Sustainable, Durable and Geographically Appropriate Roofs

Carlisle SynTec Systems has made available its RoofEd eBook for download through iTunes and Google Play.

Carlisle SynTec Systems has made available its RoofEd eBook for download through iTunes and Google Play.

Carlisle SynTec Systems has made available its RoofEd eBook for download through iTunes and Google Play. The first chapter of RoofEd focuses on EPDM roofing systems and their attributes. RoofEd contains videos, articles, case studies and photos, all of which are designed to give readers a deeper understanding of their commercial roofing system options. RoofEd can also be used as an on-the-road sales tool to help building owners choose the most sustainable, durable and geographically appropriate roof for their buildings.

After Years of Roof Leaks, a Laboratory That Produces Theatrical Equipment and Software Undergoes a Complex Reroofing

Founded in 1910, Rosco Laboratories is a multi-national producer of equipment, software and products for the theatrical, film, and television industries and architectural environment. As with every aging flat roofing system, water leakage was becoming a recurring problem at Rosco’s Stamford, Conn., facility. The severity of the leakage was further exacerbated by the lack of roof drainage (only two roof drains serviced the entire building) and poor deck slope conditions (less than 1/16 inch per foot).

The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.

The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.


Rosco representatives employed traditional methods to control and/or collect the moisture within the building by use of several water diverters. This technique was effective but Rosco representatives soon recognized this was not a viable long term solution as the physical integrity of the roof structure (deck) became a principal concern to the safety of the building occupants.

The Fisher Group LLC, an Oxford, Conn.-based building envelope consulting firm was retained by Rosco in March 2009 to survey the existing site conditions and determine the need for roofing replacement. The existing roofing construction, which consisted of a conventional two-ply, smooth-surfaced BUR with aluminized coating, exhibited numerous deficiencies (most notably severe alligatoring) and was deemed unserviceable. Construction documents, including drawings and specifications and a project phasing plan were developed by Fisher Group to address the planned roof replacement.

Bid proposals were solicited from prequalified contractors in June 2010, and F.J. Dahill Co. Inc., New Haven, Conn., was awarded the contract on the basis of lowest bid.

Existing Conditions

The building basically consists of a 1-story steel-framed structure constructed in the 1970s. It is a simple “box”-style configuration, which is conducive to manufacturing.

In conjunction with design services, destructive test cuts were made by Fisher Group in several roof sections as necessary to verify the existing roofing composition, insulation substrate, moisture entrapment, and substrate/deck construction. A total of four distinct “layers” of roofing were encountered at each test cut. The existing roofing construction consisted of alternating layers of smooth- and gravel-surfaced, multi-ply felt and bitumen built-up roofing. The bitumen contained throughout the construction was fortunately asphalt-based. Succeeding layers of roofing were spot mopped or fully mopped to the preceding layer (system). The combined weight of the roofing construction was estimated to be upwards of 20 to 22 pounds per square foot when considering the moisture content. This is excessive weight.

The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.

The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.


It is interesting to note that a minimal amount of roof insulation was present in the existing construction. Insulation was limited to a single layer of 1/2-inch-thick fiberboard. Additional insulation would need to be provided as part of the replacement roofing construction to increase the roof’s thermal performance and comply with the prescriptive requirements of the Connecticut State Energy Conservation Construction Code.

The structural substrate, or decking, is conventional in nature, comprised of poured gypsum roof decking. The roof decking incorporates 1/2-inch gypsum formboard loose laid between steel bulb-tee supports spaced about 32 inches on-center. The poured gypsum roof decking in this instance was utilized as the structural substrate and for insulating purposes. Poured gypsum roof decking has a minimal insulating value of perhaps R-2 to R-3, which is obviously considered to be minimal by present standards.

A representative number of bulk material samples were obtained by Fisher Group from the existing roofing construction as necessary to determine the material composition. The sampling included field membrane roofing plies, coatings and cements, and associated roof penetration and perimeter flashings. Laboratory analysis revealed that the second, third and, in some instances, fourth roofing “layers” (field membrane plies) contained varying amounts—5 to 10 percent—of asbestos (chrysotile) which would necessitate full abatement of the roofing construction.

PHOTOS: The Fisher Group LLC

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Project Profiles: Government

Richland County Landfill Columbia, S.C.

Petersen Aluminum roofing

Team

Roofing contractor: Aqua Seal Manufacturing and Roofing Inc., West Columbia, S.C.
Metal roof, soffit and wall manufacturer: Petersen Aluminum Corp., Elk Grove Village, Ill.

Roof Materials

The following materials were used on the roof:

  • 6,903 square feet of 24-gauge Tite-Loc in the Cityscape color
  • 1,216 square feet of 24-gauge HWP 16-inch Panel in the Cityscape color
  • 1,673 square feet of 0.032 PAC-850 Full Vent in the Cityscape color

Roof Report

Petersen Aluminum roofing
This new construction project began in early October 2012 and was completed in April 2013. Petersen Aluminum provided a complete metal system: roof, soffit and wall.

PHOTOS: Petersen Aluminum Corp.

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