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Roofing terms glossary graphic

Providing You With a Better Understanding of the Commercial Roofing Industry

Roofing can be very complex. Use this glossary of some of the most commonly used terms to familiarize yourself with the industry.

Roofing Membranes & Features | Metal Roofing | Industry Organizations

Roofing Membranes & Features

A copolymer sealant or primer formulated to prevent staining and degradation of surface coatings by preventing the migration of aromatic oils and other stains into the surface coating when installed.

The built-up roof is a multi-layer roof system that consists of multiple plies of reinforcements laid in a waterproofing bitumen. The alternating plies of reinforcement and waterproofing bitumen provide redundancy to the roof system.

Cool Roofing
A cool roof is defined as a roof surface that has both high reflectivity and high emissivity. High reflectivity requires the surfacing material to reflect solar energy away from the surface. High emissivity requires radiating heat energy away from the surface.

The ability of a membrane or coating to be stretched and lengthened by force to accommodate movement. Roofing membranes have forces exerted on them from the building movement and the membrane must be able to accommodate these movements.

Fire Resistance
The ability of a roof top material to act as a barrier to the spread of fire and confine it to the area of origin. There are established test procedures for external fire exposure to classify roof systems into Class A, B, or C ratings. Underwriters labouratories test method 790 established this procedure, which ASTM adopted and named ASTM E 108. Therefore UL 790 and ASTM E 108 is the same test with different names. Factory Mutual and Warnock Hersey both use ASTM E 108 as the primary test for fire resistance.

Low Temperature Flexibility
The ability of a membrane to remain flexible (resist cracking) after it has been exposed to low temperatures. This is vital to the long-term performance of roofing membranes in colder climates.

Modified Bitumen
The modified bitumen roof system is a hybrid built-up roof. It has the benefits of the built-in redundancy of the BUR, along with the added strength, flexibility and UV resistance of a modified membrane. The membrane consists of an asphalt and polymer blend, which allows the asphalt to take on characteristics of the polymer.

Post-Consumer Recycled Material
Post consumer recycled materials are those materials that have already served their initial purpose to a consumer and are then reclaimed rather than being discarded in traditional landfills. Common post consumer recycled materials include tires, aluminum cans, newspapers, plastic bottles, and glass.

Post-Industrial Recycled Material
Post-industrial recycled materials are those materials that have been recovered or otherwise diverted from the waste stream during the manufacturing process. This does not include used, reconditioned, or remanufactured components.

The reinforcing fabric that acts as a carrier for the polymer modified bitumen. The scrim contributes to performance characteristics of the finished product that include tensile strength, puncture resistance and fire resistance. The two primary fabrics for scrim include fiberglass and polyester. There is also a combination scrim, which incorporates both of these fabrics.

Tensile Strength
The maximum force a material can bear without tearing apart. Roofing membranes should have sufficient tensile strengths to resist the severe stresses caused by internal and external forces imposed on it. The greater the tensile strength a membrane has, the greater resistance it will have to splitting, breaking or tearing throughout its life.

Water-Based Technology
Water-based products contain no solvents and are nearly impregnable to sunlight, making them an excellent weathering surface for roofs.

Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. They are often emitted as a result of the application of roofing adhesives, sealants and primers. As the industry has shifted to using more environmentally friendly products, more low VOC and zero VOC products have emerged in the industry.

Metal Roofing

A steep slope system that is used for visual impact or aesthetics and typically requires a supporting deck with a minimum slope of 3:12. Architectural panels usually have low seam heights of 1 inch to 1-1/2 inches and do not use sealant between seams. Due to the low seam height and no sealant in the seams, architectural panels shed water but are not watertight and therefore require an underlayment below the panels to create a watertight system.

Asymmetrical Panel
Asymmetrical panels have one leg of the standing seam panel different from the other so that these legs in adjacent panels may be joined without the use of a seam cap. These asymmetrical legs usually "snap" together in a male/female connection. Examples of Garland asymmetrical panels are R-Mer® Loc and R-Mer® Clad.

Cool Roofing
A cool roof is defined as a roof surface that has both high reflectivity and high emissivity. High reflectivity requires the surfacing material to reflect solar energy away from the surface. High emissivity requires radiating heat energy away from the surface.

Flat Seam
A term used to describe when two metal panels are joined in a shingle fashion. The two panels can either be overlapped and fastened or folded and interlocked. Flat seam systems are made out of metal, which makes the roof durable, 100% recyclable and very low maintenance.

Mechanical Finishes
Mechanical finishes are raised features on metal panels. These features are mesa patterns, pencil lines, or stucco embossing. Mechanical finishes help to reduce oil canning and strengthen the panels. Garland uses mechanical finishes to increase the performance of our metal roof systems, and also to add to their aesthetic appeal.

Mechanically Curved
To create a curved profile in a metal panel, a machine is used to form the panel to a desired radius, hence the term, mechanically curved. Some manufacturers do not mechanically curve their panels; installers simply force straight panels to conform to the curve in a roof, which can cause binding of standing seam panels on their clips, oil canning, and failure. Garland has the ability to mechanically curve our symmetrical panels to the tightest radius available in the industry.

Oil Canning
Oil canning is triggered by thermal expansion and contraction of metal roof panels and flashing. Oil canning can be seen as a rolling or washboard bending of a piece of metal. To limit oil canning to a minimum, Garland designs our roofing systems with unlimited thermal movement, uses high quality roll forming equipment, and adds mechanical finishes to metal roof panels and accessories.

Standing Seam
A term used to describe the adjoining of two metal panels together with an upturned portion of the metal. The two panels are held together with concealed clips. The raised seam is above the drainage plain. Standing seam systems are made out of metal, which makes the roof durable, 100% recyclable and very low maintenance.

A low slope system that can support their own weight without a deck. Structural panels usually have high seams 1-3/4 inches to 3 inches and can handle slopes as low as 1/4:12. The panels are watertight and can span long distances. Since a deck is usually not required, a structural system can end up being a lower cost alternative than an architectural panel with a supporting roof deck.

Symmetrical Panel
A symmetrical panel design has both legs of the standing seam panel identical in size and shape. This is typically found in panel systems where a cap is used to seam the panels together. Benefits of a symmetrical panel are easy replacement and tighter curving radiuses. Examples of Garland symmetrical panels are our structural system, R-Mer® Span, and our architectural system, R-Mer® Seam. Due to its symmetrical design with a seam cap, R-Mer Span has the highest rated uplift pressures resistance in the industry.

Thermal Bridging
A condition where heat or cold can be conducted through a metal fastener or opening from the underside of the roof assembly to the outside of a roof surface. Properly designed roof assemblies will eliminate thermal bridging from occurring.

Unlimited Thermal Movement
The term "unlimited thermal movement" describes designing a roof system to accommodate all of the expansion and contraction that a roof may experience throughout a 200-degree cycle. With a metal roof, this movement can be in the order of several inches. The Garland standing seam one-piece clip design allows the metal roof panels to move freely through an unlimited range of expansion and contraction. Garland's flat seam metal roof system, R-Mer Lite®, is also designed with the unlimited thermal movement concept.

Wind Uplift
A wind uplift rating is not the miles per hour of wind speed a roof system can withstand, but rather, the negative pressure (pounds per square foot) that occurs when the inside air pressure of a building is greater than the air pressure outside the building. Most parts of North America require a 1-60 or 1-90 uplift resistance. Coastal regions and high wind areas may require additional uplift resistance.

Industry Organizations

The Cool Roof Rating Council (CRRC) is an independent, non-profit organization that maintains a third-party rating system for thermal emittance properties of roof surfacing materials. It was created in 1998 to develop accurate and credible methods for evaluating and labeling the solar reflectance and thermal emittance (radiative properties) of roofing products and to disseminate the information to all interested properties.

The ENERGY STAR Program represents a voluntary partnership between businesses and organizations and the federal government to promote energy efficiency and environmental activities. ENERGY STAR labeled roof products are reflective and lower roof surface temperature by up to 100oF (37.70C), decreasing the amount of heat transferred into a building.

The Leadership in Energy and Environmental Design (LEED) Green Building Rating System, developed by the U.S. Green Building Council, is a third-party certification program and the nationally accepted benchmark for the design, construction, and operation of high-performance green buildings.

Title 24, Part 6
Title 24 of the California Code of Regulations, known as the California Building Standards Code or just “Title 24” contains the regulations that govern the construction of buildings in California.

UL Environment
UL Environment supports the growth and development of sustainable products, services and organizations in the global marketplace through standards development, educational services and independent third-party assessment and certification. Specific environmental solutions services UL Environment provides include environmental claims validation, sustainable products certification, energy efficiency certification, environmental product declarations and advisory services.