A LEARNING EXPERIENCE

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

by Krista Reisdorf

As published in NRCA's Professional Roofing magazine, April 2007. www.nrca.net

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.

Photos courtesy of Harbert Roofing Inc., Redding, Calif.
Grasses installed over the membrane

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.







Ornamental grasses were planted over the membrane.






"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.

Ornamental grasses were planted over the membrane.

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)."

An employee from International Leak Detection, Ontario, lays out the Electric Field Vector Mapping.

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.

FLOOD TESTING

CANADIAN ROOFING CONTRACTORS’ ASSOCIATION
ASSOCIATION CANADIENNE DES ENTREPRENEURS EN COUVERTURE
100-2430 Don Reid Drive · Ottawa, Ontario · K1H 1E1 · Tel: 800/461-2722 · 613/232-6724 · Fax: 613/232-2893
Website: www.roofingcanada.com · E-mail: crca@on.aibn.com

ADVISORY BULLETIN MARCH 2007

FLOOD TESTING

Upon completion of a roof installation, many owners wish to verify the integrity of construction prior to “taking possession”. Some designers and consultants specify that a flood test of the roof be carried out as a means of assuring that the roof has been properly built. The CRCA National Technical Committee does not support this practice, believing that flood testing is not a reliable quality assurance method and that the risks associated with flood testing far outweigh any potential benefits.

Flood testing will not provide useful information about the quality of the roof design or installation, nor about the durability of the materials used. It may, if the depth of water is sufficient, indicate whether there is a breach in the membrane, but it will not confirm the overall ability of the roof to provide satisfactory service throughout its expected service life. The ability to resist wind and impact loads, to remain dimensionally stable, to resist temperature induced stress and numerous other attributes are as important for the long term performance of the roof.

Flood testing can cause irreparable damage to the roofing system, or even the supporting structure. Water weighs 1000 kg/m3 (62.4 lb/ft³). If a flood test calls for a depth of 50 mm (2 in), it would add 50 kg/m2 (10 lb/ft²) to the dead load. However, most roofs, when properly constructed, are positively sloped to drains. CRCA together with many other industry organizations, recommend a minimum slope of 2%.

A simple example will demonstrate how this will significantly increase the load on the roof. Assume a roof is divided into basins of 15 m (50 ft) in length and width. Also assume that it is sloped at 2% to a drain in the centre of the basin. We know that the water, having a density of 1000 kg/m³ (62.4 lb/ft³), covering the roof with a uniform depth of 50 mm (2 in) weighs 50kg/m2 (10 lb/ft²). Over the entire area of the roof basin (225 m², or 2500 ft²) the standing water at a uniform depth of 50 mm (2in) would weigh 11250 kg (25,000 lb). The additional volume of water in the basin resulting from the slope is 1/3 (15 m x 15 m x 0.15 m) = 11.25 m3 (400 ft³) which weighs a total of 11,250 kg (25,000 lb), or 50 kg/m2 (10 lb/ft²) if divided uniformly over the roof. The total combined uniform weight of the water is, therefore, approximately 100 kg/m2 (20 lb/ft²). The capacity of roofs constructed to near their design load limits may be exceeded by this weight of the water.

Properly constructed low-slope roofs are positively drained and are not designed to withstand large hydrostatic pressure loads. Fifty millimetres of water over the roof will exert a static fluid pressure of ˜72.5 kPa (10.5 psi). The pressure increases to over 215 kPa (31.25 psi) when the depth increases to150 mm (6 in), as would occur over the drain sump as in the example of a sloped basin.

The opinions expressed herein are those of the CRCA National Technical Committee. This Advisory Bulletin is circulated for the purpose of bringing roofing information to the attention of the reader. The data, commentary, opinions and conclusions, if any, are not intended to provide the reader with conclusive technical advice and the reader should not act only on the roofing information contained in this Advisory Bulletin without seeking specific professional, engineering or architectural advice. Neither the CRCA nor any of its officers, directors, members or employees assumes any responsibility for any of the roofing information contained herein or the consequences of any interpretation which the reader may take from such information.

Although a membrane properly supported in the field of the roof should be able to resist these pressures, transitions and joints that rely on sealants, compression bars etc, may fail under such loads resulting in leakage. Should there be a weakness in the membrane, transitions, or edges of the roofing system, significant water ingression may occur, damaging the roof components, interior finishes and building contents. It should also be remembered that in the event of a leak occurring, it could not be stopped until all of the water is effectively drained from the roofs. By then the damage will have been done.

The safety of those individuals conducting the flood test must also be considered. A roof covered in water is difficult and hazardous to walk upon. When the drain plug is removed, the force of the draining water has sufficient force to suck a worker’s arm into the drain causing serious injury. In addition, the force of the whirlpooling water may damage drain and pipe connections.

Although flood testing is not recommended for roof applications, it may be a useful method for determining the integrity of waterproofing systems. Waterproofing systems are designed and constructed to resist substantial hydrostatic loads while in service. By example, the National Roofing Contractors Association (NRCA) recommends a minimum of 5 plies of reinforcement in an asphalt built-up membrane where the anticipated hydrostatic pressure head that needs to be resisted is 7.9 to 15.2 m (26 to 50 ft). Due to the difficulty in uncovering a waterproofing membrane, it is prudent to conduct a flood test to verify that they will be leak free under such loads.

For roofing applications, however, where such pressures are not expected during service, flood testing will provide little useful information about the performance properties of the roof. There are many alternate non-destructive methods of evaluating the quality of the roof system that are far more reliable —Infrared Thermography, Electrical Capacitance (Impedance) Testing, Nuclear Moisture Testing and Electric Field Vector Mapping (EFVM). The National Technical Committee of CRCA believes, however, that the most effective means of ensuring the satisfactory performance of the roof is by hiring a reputable roofing contractor and on-site monitoring of the installation by a knowledgeable roof observer.

Note: Much of the information contained in this Advisory Bulletin is taken from an article by J.P. Crowe, titled Water, Water Everywhere that appeared in the February 2006 issue of Professional Roofing. Information on how to acquire a copy of the entire article can be obtained at www.professionalroofing.net.

EFVM - A NEW LEAK DETECTION TECHNIQUE

by Chris Eichhorn, International Leak Detection & Charlie Miller, Roofscapes Inc.

Electric field vector mapping (EFVM*), a new and powerful tool for improving quality control of waterproofing systems, is now available. Although this method is unfamiliar
to most Americans, it has already achieved a long record of success in Europe.

Unlike most other leak detection methods, it can quickly and accurately locate the point
of water entry. Another unique aspect of this technique is that a pinhole (too small to find visually) is as easy to locate as a large tear or failed seam. Alternative approaches, such
as infrared surveys, can determine where water has accumulated in the insulation, but may
not be as useful in actually finding the waterproofing defect.

The EFVM* technique uses water as the electrically conductive medium. The survey technician installs a wire loop around the perimeter of the area to be tested and introduces an electrical potential. The area within the loop is dampened to form an upper electrical ‘plate’. The structural deck is the lower electrical plate, while the membrane separating the two plates acts as the insulator. If moisture enters a defect in the membrane, an electrical contact is established between the two plates (i.e., an electrical ground). The survey technician can then follow the direction of the electric field to the membrane defect. (Special procedures are required when using EFVM on projects with supplementary root barriers. The root-barrier membrane will act like an insulating layer. Therefore, it is necessary to make small incisions in the root-barrier to establish electrical contact with the underlying waterproofing membrane. These incisions can be re-sealed after the leak is located.)

The technique was pioneered in Germany by AB Flachdach Mess und Trocknungstechnik GmbH (AB Flachdach) in Germany. It is now available through their North American partner, International Leak Detection, Ltd. in Ontario, and through Roofscapes, Inc., a nation-wide green roof provider based in Philadelphia.

The benefits of EFVM* can be summarized as follows:
· Locates defects precisely, enabling efficient repairs
· Able to re-test repairs immediately
· Can be used AFTER cover systems are installed, especially with ‘green roof’ landscapes
· Less expensive than conventional flood testing
· Eliminates the hazard of overloading structural decks during testing, since ponding water
· is NOT part of the testing procedure
· Can be used on steeply sloping roof surfaces where flood testing is impossible

EFVM* has been used successfully with a wide range of waterproofing materials in Germany.
AB Flachdach has electronically surveyed 35 million square feet of roof membrane in the
past five years. However, an even broader range of waterproofing materials is in use in North America. The suitability of EFVM* depends on the electrical resistance of the water-proofing materials. In particular, EPDM membranes vary in their electrical properties, and some formulations containing carbon black may not be compatible. Aluminized protective coatings, commonly used in the US in conjunction with modified bituminous membranes, may also defeat the technique.

International Leak Detection Ltd. can conduct bench-scale tests in order to establish that EFVM* is suitable for a particular waterproofing material. EFVM* can also be used on all types of roof decks, including steel, concrete, and wood. (A special ‘grounding grid’ must be introduced in this case.)

The EFVM* method has proven highly advantageous in situations where the water-proofing is concealed or buried. These include IRMA (Inverted Roof Membrane Assembly) configurations, plaza installations, ballasted roofs, and ‘green roofs.’ Green roofs are veneer landscapes installed on top of conventional roofs. They may be anywhere from 2.5 inches to 3 feet deep. Without an effective method of locating defects, leak location and repair could become very expensive on these systems. For this reason, Roofscapes, Inc. offers the EFVM* technique as a standard option in its green roof installations. Currently, EFVM* is being used on numerous Roofscapes projects, including Point Defiance Zoo in Washington State, and a large chiropractic center in Pennsylvania.

A recent project in Frankfurt, Germany, illustrates the value of EFVM* as a loss prevention technique. This project involved an 110,000-square foot roof that was installed in 2000. The technicians found 17 defects in the membrane. Some of these flaws were located in defective seams (workmanship) but others were tiny punctures. There was no visible water damage in the interior of the building. The building owners did not know that there were any problems and probably would not have found the flaws until the insulation had become saturated.

For more information please contact:
Chris Eichhorn at International Leak Detection Ltd. (chris@leak-detection.com); or
Charlie Miller at Roofscapes, Inc. (cmiller@roofmeadow.com).

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