A learning experience

Harbert Roofing Inc. installs its first green roof system on Shasta County Library


When the Shasta County Library in Redding, Calif., needed roof systems installed on its new building, the project was put out for public bid. The general contractor that was awarded the project determined which roofing contractor would install the roof systems on the building.

So Harbert Roofing Inc., Redding, was pleased the general contractor chosen was one with which Harbert Roofing has a close working relationship. As a result, Harbert Roofing was chosen to install the new roof systems on the Shasta County Library and given the opportunity to try something it never had done before—install a green roof system.

A choice

Harbert Roofing's relationship with Carlisle, Pa.-based Carlisle SynTec Inc. and experience with its products led Harbert Roofing to choose a Carlisle SynTec system for the project.

"We specified Carlisle SynTec 0.080-mil-thick Sure-Weld® TPO single-ply membrane roof system on the main library roof," says Howard Harbert Jr., vice president of Harbert Roofing.

The company also was asked to install 30 squares of Metal Sales Manufacturing Corp.'s Vertical Seam panels at the clerestory overlooking the garden, as well as Metal Sales Manufacturing Clip-Loc metal panels on the shed roof and at the library entrance. In addition, a 6,000-square-foot green roof system was requested for the lower section of the library, which can be seen from inside the building.

Additionally, Harbert Roofing was asked to perform below-grade waterproofing and wall waterproofing, as well as supply and install reglet as needed.

Layers

The green roof system installation was complex, consisting of many layers.

"With help from Carlisle SynTec's technical department, we had basic training to become more familiar with green roof installation and began the installation by installing Carlisle SynTec Polyiso Insulation set in a layer of hot asphalt over a structural concrete deck and layer of 1/2-inch-thick DensDeck Prime," Harbert says. "Next, we laid Carlisle SynTec 0.080-mil-thick Sure-Weld TPO membrane and stripped in all field seams and wall seams with a 6-inch-wide membrane with a double welder and seam patched all T-joints. Fully adhered 0.080-mil-thick TPO provides greater puncture resistance and breaking strength.

"We then laid down a layer of CCW 300 Protection Fabric, which is used to resist soil chemicals, mildew and insects and is nonbiodegradable," he continues. "We installed Carlisle SynTec Sure-Seal HP Protective Mat, which is used as a slip sheet in this application, and then installed Carlisle SynTec Non-Reinforced Polypropylene Geomembrane. The geo­membrane is formulated for long-term use in buried applications."

The company then installed Carlisle SynTec's CCW MiraDrain Drainage Board, which has a polystyrene core with pierced holes, allowing water retention and drain-age. A Carlisle SynTec Moisture Retention Mat, which is designed to retain moisture in roof gardens, also was installed.

McEntire Landscaping, Redding, installed the roof system's irrigation system, growth media and plants.

For the main library's roof, Harbert Roofing installed a layer of Carlisle SynTec 4-inch-thick Sure-Seal polyisocya-nurate insulation, Carlisle Crickets and 1/2-inch-thick DensDeck Prime over a structural metal deck. The 0.080-mil-thick Sure-Weld TPO single-ply membrane then was mechanically fastened.

The company also installed a metal roof system over a structural metal deck at the clerestory overlooking the garden roof.

"We began this installation using RMAX nail base and a layer of Grace Construction Products Vycor® underlayment," Harbert says. "Next, we installed a layer of Fontana 30-pound felt and Metal Sales Manufacturing 18-inch Vertical Seam metal panels."

A metal roof was installed over the building's book drop, as well. Harbert Roofing applied peel-and-stick Metal Sales Manufacturing High-Temp underlayment and installed Metal Sales Manufacturing 16-inch Clip-Lok panels.

Waterproofing work also was performed during the installation.

"At the elevator pit, we used Grace Construction Products PrePrufe® 160R under the concrete," Harbert says. "After the concrete was poured, we used one layer of Grace Construction Products Bituthene® 4000 and Grace Construction Products Hydroduct® 220 protection board, which are peel-and-stick products.

"In addition, we installed Grace Construction Products peel-and-stick Perm-A-Barrier® Wall Membrane on top of all the parapet walls that received stucco and mechanically fastened about 3,000 linear feet of Fry STX reglet," he continues.

As a safety precaution, the company employed a standard 6-foot barrier around the roof using safety cones and rope to indicate the roof's edge.

A test

Harbert Roofing not only installed three roof systems but installed a roof system it never had installed before.

"This was our first green roof system installation," Harbert says. "We are not aware of any other green roofs in northern California-certainly not north of Sacramento. This installation was different from a typical single-ply roof system installation because of the extra layers of protection installed over the single-ply roof system. These layers protect the single-ply membrane from punctures that could occur when the landscaping company installs the growth media and other garden amenities, as well as offer protection for ongoing green roof maintenance."

Harbert Roofing's work was put to the test after the green roof system was installed.

"The specifications required that the green roof installation be certified by a third party to ensure there were no leaks before installing the protective layers of roofing products and growth media," Harbert says. "This testing was performed by International Leak Detection, Ontario. They use a method referred to as Electric Field Vector Mapping® (EFVM)."

During this process, an electrical potential difference is set up between the membrane surface and structural deck. If there are leaks, the electrical current will help detect them by flowing to the source. An EFVM Potentiometer then is connected to two probes on the membrane surface to identify the direction of the electrical current and find the puncture or breach.

"At the conclusion of the EFVM test, we were told we passed with 100 percent, meaning there were no leaks detected," Harbert says. "International Leak Detection also told us we were one of only a few that ever has passed this test with 100 percent upon first inspection."

Working together

Coordination was helpful when the company was installing the roof systems.

"There were many consultants, architects, material suppliers and crew members involved during the project, and we had to make sure we were in tune with everyone," Harbert says. "A lot of time was spent coordinating submittals before we could order materials.

"We worked closely with Dick Gillenwater, manager of Advanced Proj­ects an­­d Green Roof Systems for Carlisle SynTec, through numerous e-mails and telephone calls to perfect our submittals and the green roof installation," he continues.

The experience was valuable for the roofing company.

"We are one of a few roofing contractors in Redding that performs single-ply roofing, and we want to stay on the leading edge of technology," Harbert says. "We thought this project would be a great learning experience and allow our company to gain more valuable experience."

Krista Reisdorf is managing editor of Professional Roofing magazine.



Project name: Shasta County Library
Project location: Redding, Calif.
Project duration: Feb. 21, 2006-Aug. 30, 2006
Roof system type: Green roof, single-ply and metal
Roofing contractor: Harbert Roofing Inc., Redding, Calif.
Roofing manufacturer: Carlisle SynTec Inc., Carlisle, Pa.; Metal Sales Manufacturing Corp., Woodland, Calif.; and Grace Construction Products, Cambridge, Mass.

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