About Michael Fischer

Michael Fischer is the Washington, D.C.-based Roof Coatings Manufacturers Association’s director of codes and standards. He is a member of the International Code Council and the ICC Industry Advisory Committee, as well as ASTM International.

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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Coating a Roof? Don’t Forget Fire Ratings

Fire tests are one of the most important system tests for roof coatings, and it is essential when specifying and applying a coating over an existing roof in a maintenance or repair setting to ensure the roof system’s fire rating is not negatively affected.

TEST METHODS FOR FIRE TESTS

The International Building Code (IBC), first published in 2000, brought together several regional codes into one central, national code and facilitated the acceleration of code adoptions across the U.S. Today, most of the U.S. follows a statewide adoption process for the IBC for Roof Assemblies and Rooftop Structures; some areas do not, which can make code enforcement tricky. Some areas still follow local adoption and may refer to older versions of the code instead of the most current 2012 IBC.

According to the most recent IBC, roof assemblies and coverings are divided into classes A, B, C or “Nonclassified” and are tested in accordance with UL 790 or ASTM E 108. These tests measure the spread of flame, recording whether the material you put on the roof will cause the flame to spread too far on the roof. The UL 790 inaugurated modern fire tests about 100 years ago and, as such, incorporates a century of data and history about roof coatings that may broaden the reach of what certifications the test provides.

“Many see UL 790 as the preferred fire test,” notes Steve Heinje, technical service manager with Quest Construction Products LLC. “It is interesting to note the ASTM E 108 test is deemed by the code requirements an equivalent test.” The ASTM E 108 is a consensus version of UL 790 and can be run by any qualified and accredited test laboratory. Many test laboratories, such as FM Approvals, conduct testing using ASTM E 108.

COMPONENTS OF FIRE TESTING

The roof coating is just one component in the fire rating of a roof assembly; other components include slope, the coating substrate, whether the roof deck is combustible and whether the roof is insulated. These factors, taken together, will determine the roof system’s fire rating.

SLOPE
Although there are exceptions, most fire ratings are done for slopes of under 3/4 inch for commercial roofs, and coatings tend to be recommended for application to a roof with 2 inches or less slope. Slope is an important factor to consider because special coatings may be needed for high slope transitions.

SUBSTRATE
The substrate or membrane type is another vital component of fire testing because the substrate to which the coating is applied could affect the flammability of the roof system. When coating over an existing roof, one should note what existing roofing substrate is being coated over—whether it’s BUR, mod bit, concrete, metal, asphalt or another type of substrate.

COMBUSTIBLE VS. NON-COMBUSTIBLE ROOF DECK
Most coatings are tested over noncombustible decks, but additional and challenging tests are required for the use of combustible decks. It is much more difficult to achieve a Class A rating when covering a wood deck.

INSULATION
Again, it is important to note the materials of the existing roof being coated because these components can affect the flammability of the roof system. Polymeric insulations often reduce the allowable slope for a given system.

PROPER APPLICATION OF THE ROOF COATING

Another significant consideration is that the coating is applied at the appropriate thickness and rate.

“One big thing out of the coating manufacturer’s control is that the applicator uses the recommended or test-required thickness and/or rate at the point of application,” points out Skip Leonard, technical services director with Henry Co. Proper application encompasses parameters, such as the final dry-film thickness, the use of granules or gravel, use of reinforcements and even the number of coats. Accounting for these details is an integral part of installing a rated system.

Once assembled, the roof covering will be granted a Class A, B or C rating by approved testing agencies, typically through UL 790 or ASTM E 108, depending on how effective the roof proves to be in terms of fire resistance. Rated coating solutions exist for just about any existing roof system recover or coating application and often can achieve a Class A rating.

Learn More
Visit the Roof Coatings Manufacturers Association website to locate a roof-coating manufacturer who can help you choose a roof coating most appropriate for your roof system. For more information about roof-coating fire ratings, check out FM Approval’s RoofNav online database for up-to-date roofing-related information or the UL Online Certifications Directory.