Understanding FM 1-52
August 21, 2019
There are two recognized field test methods for determining uplift resistance of adhered membrane roof systems, both of which can be problematic:
  1. ASTM E907, "Standard Test Method for Field Testing Uplift Resistance of Adhered Membrane Roofing Systems," and 
  2. FM Global Loss Prevention Data Sheet 1-52 (FM 1-52), "Field Verification of Roof Wind Uplift Resistance." 
Both test methods provide for affixing a 5’ x 5’ dome-like chamber to the roof’s surface and applying a defined negative (uplift) pressure inside the chamber to the roof system's exterior-side surface using a vacuum pump, like in the photo below. 

An example of a test chamber used for negative-pressure uplift testing

However, ASTM E907 and FM 1-52 differ notably in their test cycles and maximum test pressures for determining roof system deflections and whether a roof system passes or is “suspect”.
  • Using ASTM E907, a roof system is “suspect” if the deflection measured during the test is 25 mm (about 1 inch) or greater. 
  • Using FM 1-52, a roof system is “suspect” if the measured deflection is between ¼ of an inch and 15/16 of an inch, depending on the maximum test pressure; 1 inch where a thin cover board is used; or 2 inches where a thin cover board or flexible, mechanically attached insulation is used. 
Test results' reliability 
The reliability of the results derived from ASTM E907 and FM 1-52 is a concern, especially when the tests are used for quality assurance purposes. A note in ASTM E907 acknowledges its test viability. "Deflection due to negative pressure will potentially vary at different locations because of varying stiffness of the roof system assembly. Stiffness of a roof system assembly, including the deck, is influenced by the location of mechanical fasteners, thickness of insulation, stiffness of deck, and by the type, proximity, and rigidity of connections between the deck and framing system."

For example, when testing an adhered roof system over a steel roof deck, placement of the test chamber relative to the deck supports (bar joists) can have a significant effect on the test results. If positioned between deck supports, the test chamber's deflection gauge will measure roof assembly deflection at the deck's midspan, which is the point of maximum deck deflection. Also, in many instances, field-uplift testing results in steel roof deck overstress and deck deflections far in excess of design values, which can result in roof system failure. These situations can result in false “suspect” determinations of a roof system.

Industry position/recommendations

Because of the known variability in test results using ASTM E907 and FM 1-52 and the lack of correlation between laboratory uplift-resistance testing and field-uplift testing, the roofing industry considers field-uplift testing to be inappropriate for use as a post-installation quality-assurance measure for membrane roof systems.

Conclusion

FM 1-52 is an FM Global-promulgated evaluation method and not a recognized industry-consensus test standard. The scope of FM 1-52 indicates that it’s only intended to confirm acceptable wind-uplift resistance on completed roof systems in hurricane-prone regions, where a partial blow-off has occurred, or where inferior roof system construction is suspected or known to be present.

FM 1-52 was originally published by FM Global in October 1970. The negative-pressure uplift test was added in August 1980 and has been revised several times. The current edition is dated July 2012 and includes an option for "visual construction observation (VCO)" as an alternative to negative-pressure uplift testing. VCO provides for full-time, third-party monitoring to verify roof system installation is in accordance with contract documents.

For more information, contact Craig Tyler
November 6, 2019
Ballasted Roofs – A New Look at an Old System

While ballasted roof systems aren't as popular today as they used to be, they are still being installed successfully across the country. Stone-ballasted roof systems began appearing sometime in the early 1970s. While they appear superficially similar to built-up roofing (BUR), there are major differences between the two systems. Both are topped with rocks, but BUR uses a thin layer of pea gravel or crushed stone no larger than a quarter-inch diameter partially embedded into the asphalt topcoat to protect it from the sun's UV rays. In a ballasted roof, the stones are much larger - at least an inch in diameter - and applied much more heavily. In fact, the weight of the stone ballast is what holds the roof components in place. The weight can vary from 10 pounds per square foot (the minimum allowed by code) to 25 pounds or more. The most common ballasted assembly was a loose-laid EPDM membrane over a rigid insulation board. By the 1980s, designers were integrating concrete pavers into ballasted roof designs, creating access paths, pedestrian walkways, and even rooftop plazas. When the green building movement came along in the late 1990s, it was natural to transition the ballast from stone to soil, creating vegetated or "green" roofs. Ballasted roofs are loose-laid; this means the contractor can assemble all the components, including the roofing membrane and insulation, without fastening them to each other or the roof deck. Membrane seams are sealed, of course, and the waterproofing layer is secured to the parapet and at roof penetrations, but it isn't adhered to the roof deck or the layers beneath it. By eliminating nearly all the adhesives and fasteners other assemblies require, ballasted roofs typically cost less and are quicker to install than other systems. EPDM is popular because it can be ordered in large sheet sizes, which minimizes seaming. TPO and PVC are also popular as single-ply roofing membranes under ballast. For designers, ballasted roofs provide a natural-looking surface that blends well with a range of architectural styles. With paver-ballasted designs, the roof can become a plaza, patio, or other usable outdoor space suitable for recreation, walking, or relaxation.  For the building owner, ballasted roofs are durable and long lasting. Stones or concrete pavers protect the waterproofing layer from UV rays, hail, and foot traffic. If repairs are needed, the loose-laid layers are easily taken up. And at the end of the roof's designed lifespan, the lack of adhesives ensures the membrane will be fully recyclable. Advantages Economy: Ballasted roofs use economical materials and are among the fastest to install. In fact, they have one of the lowest lifecycle costs of any roofing system on the market today. Scheduling: These roofs can be installed in a wide range of weather and temperature conditions, and close in the building envelope faster than most other systems. For occupied buildings, there are no offensive smells associated with the install. Aesthetics: Ballast can vary from large round cobblestones to pavers. This natural look is appealing to many building owners and architects. Rock can be combined with pavers to provide a variety of textures and utilitarian purposes. Amenity Space: With proper planning, ballasted roofs are suitable for plaza decks, walking paths, recreation areas, and other uses. Energy Efficiency: Ballasted roofs reduce heating and cooling loads. A system with a weight of 17 pounds per square foot saves as much energy as an ENERGY STAR-rated reflective roof. Fireproof: Stone and concrete are virtually fireproof, so ballasted roofs provide the highest fire rating available. Class-A fire resistance can be achieved without gypsum board underlayments or expensive fire-retardant chemicals. Durable: The stone or concrete pavers also provide protection from UV rays, hail, foot traffic, and extreme temperature fluctuations. Ease of Repair: Removal and re-installation of the ballast and insulation is easy, and both can be reused. No adhesives or fasteners are used, so it's easy to separate the components. Even in a complete replacement of the waterproofing membrane, the ballast stone or concrete pavers can be reinstalled. Recyclable: Most of the components are reusable and/or recyclable. Rocks, pavers, and rigid insulation board can be reused. The unadhered membrane is easy to remove and recycle. Stormwater Management: Green roofs and other options like Carlisle's Stormwater Retention Option can retain as much as 65% of the rainwater that falls during a storm. This can help owners and developers reduce fees.  Consult the EPDM Specification on the Carlisle SynTec Website here or consult the Ballasted Stormwater Retention Brochure here or contact Craig Tyler at [email protected] for further questions.

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October 16, 2019
Electronic Leak Detection for Roofing Systems

A building’s roofing system separates the damaging outdoor environment from the valuable interior contents. To be effective, it must be watertight. Although roof systems are inspected and sometimes flood tested prior to warranty issuance, small, difficult-to-see breaches in the membrane system can go unnoticed until damaging water leaks occur inside the building. Moreover, once a leak has developed it can be extremely difficult to locate the leak and perform the necessary repair, especially when overburden materials are installed. Enter Electronic Leak Detection, otherwise known as ELD. ELD systems have been around for 20+ years and are gaining popularity due to some revolutionary new products that have expanded testing capabilities. ELD systems come in two main varieties: low-voltage and high-voltage, with low-voltage being the most common. ELD systems work by creating an electrical potential difference between a non-conductive roof membrane and a grounded conductive structural deck or substrate. Testing is performed by applying water, which is conductive, to the surface of the roof membrane. The roof membrane will isolate the potential electrical difference between the deck and the water, but when a breach is present, the water will create an electrical connection to the grounded deck, pinpointing the exact leak location to the testing technician. A major benefit of ELD testing is that it can be performed at any time, even after overburden materials are installed. For ELD systems to be effective, a conductive substrate must be present directly below the membrane’s surface. Due to this requirement, membrane choice and application method can be limited. Two ELD companies that Carlisle has experience with are International Leak Detection (ILD) and Detec Systems. Products from either of these companies are permitted for use in a Carlisle warranted roof system but are not covered in the Carlisle warranty. ILD has been around since 2001 and promotes a conductive mesh that must be installed directly below the membrane for accurate testing of membrane systems over non-conductive decks. Due to the design of the conductive mesh, it is only acceptable for use under thermoplastic FleeceBACK® membranes adhered with FAST™ or Flexible FAST Adhesive. Detec Systems promotes a conductive primer called TruGround® that is roller-applied over the top layer of insulation, prior to adhesive application. Once dried, the membrane system can be installed as usual. TruGround conductive primer expands ELD testing capabilities, as it is suitable for use with bareback membranes and even black EPDM, which historically has not been compatible with ELD testing. Carlisle SynTec Systems has secured FM approvals for Detec’s TruGround in a number of different roofing assemblies. Those assemblies include: EPDM and TPO with CAV-GRIP® III adhesive over SecurShield®, SecurShield HD, DensDeck® Prime, and SECUROCK®. PVC with Low-VOC Bonding Adhesive over InsulBase®, SecurShield, SecurShield HD, and SecurShield HD Plus.  Contact Chris Kann with questions regarding ELD systems.

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September 18, 2019
Fire Performance of Polyiso

All construction materials, including foam plastics such as polyiso insulation, must provide a suitable margin of fire safety. Polyiso possesses a high level of inherent fire resistance when compared to other foam plastic insulations due to its unique structure of strong isocyanurate chemical bonds. These bonds result in improved high-temperature resistance (up to 390°F [199°C], more than twice that of other building insulation foams) which in turn leads to enhanced fire resistance. In addition, because polyiso does not melt or drip when exposed to flame, but rather forms a protective surface char, its fire resistance is further enhanced, especially in terms of flame spread and flashover potential. Polyiso passes both the ANSI UL 1256 and FM 4450 fire tests without a thermal barrier. Polyiso, a thermoset material, stays intact during fire exposure in the ASTM E84 or "Tunnel Test.” It forms a protective char layer and remains in place during the test, thereby meeting all building code requirements and contributing to a fire-safe building. For more information on polyiso’s performance in fire tests, visit the 'Technical Bulletins’ page on the PIMA (Polyiso Manufacturers Association) Website where you can find the following papers: Technical Bulletin 103: Fire Performance in Walls and Ceilings Discusses polyiso insulation as it relates to building codes in construction and fire tests in walls and ceilings, including ASTM E84 and ASTM E119. Technical Bulletin 104: Fire Performance in Roof Systems Provides an overview of polyiso insulation requirements for roof systems and key issues in fire performance, including the importance of the FM 4450 Calorimeter Tests and the UL 1256 Resistance to Interior Spread of Flame test. Technical Bulletin 105: Fire Test Definitions Provides an in-depth look at fire test procedures for building applications. Technical Bulletin 111: Class A and Class 1 Roof Assemblies Are Not the Same Explains why Class 1 and Class A are not the same. Technical Bulletin 111C: Roofing Regulations in Canada – Class A and Class 1 Roof Assemblies Are Not the Same Explains why Class 1 and Class A are not the same. Technical Bulletin 405: Fire Resistance Properties of Polyiso Foam Plastic Insulation Used in Wall Assemblies – Facts and Comparisons Looks at the minimum fire resistance properties required for foam plastic insulation and compares data on polyiso with other recognized combustible materials. Product Stewardship Paper 100: Polyiso Insulation and Flame Retardants New Product Stewardship report on polyiso and flame retardants. Contact Craig Tyler at [email protected] with questions.

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