Glossary of Roofing and Waterproofing Terms

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ICBO: International Conference of Building Officials. Author of The Uniform Building Code.

Ice Dam: a mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the overhang of a steep roof, causing ice and water to back up under roofing materials.

Ignition Temperature: the minimum temperature to which a solid, liquid, or gas must be heated in order to initiate or cause self-sustained combustion independent of the heating element.

Impact Resistance: the ability of a roofing material to resist damage (e.g., puncturing) from falling objects, application equipment, foot traffic, etc. The impact resistance of the roofing assembly is a function of all of its components, not just the membrane itself.

Impregnate: to coat, saturate, and/or surround the fibers of a reinforcing mat or fabric with an enveloping liquid material, (e.g., bitumen, elastomeric compound, etc.).

Incline: the slope of a roof expressed either in percent or in the number of vertical units of rise per horizontal units of run. (See Slope.)

Infrared Thermography: a practice of roof system analysis where an infrared camera is used to measure the temperature differential of a roof surface to locate areas of underlying wet or moist insulation. (See Thermal Image.)

Inorganic: any chemical or compound that is derived from minerals, does not contain carbon, and is not classified as organic; being or composed of materials other than hydrocarbons and their derivatives; not of plant or animal origin.

Insect Screen: wire mesh used to prevent insects from entering the building through ventilators, louvers, or other openings.

Insulation: any of a variety of materials designed to reduce the flow of heat, either from or into a building. (See also Thermal Insulation.)

Intake Ventilation: the fresh air that is drawn into a passive ventilation system through vents typically installed in the soffit or eave of a roof.

Interlayment: a felt, metal, or membrane sheet material used between courses of steep-slope roofing to improve the weather- and water-shedding characteristics of the primary roof covering during times of winddriven rain and snow. Typically used with wood shakes.

Interlocking Shingles: individual shingles that mechanically attach to each other to provide wind resistance.

Internal Pressure: pressure inside a building that is a function of ventilating equipment, wind velocity, and the number and location of openings and air leaks.

Inverted Roof Membrane Assembly (IRMA`): a patented, proprietary variation of the "Protected Membrane Roof Assembly" in which Styrofoam Brand Insulation and ballast are placed over the roof membrane. IRMA™ and Styrofoam are registered trademarks of the Dow Chemical Company.

IRWC: Institute of Roofing and Waterproofing Consultants

ISANTA: International Staple, Nail & Tool Association

Isocyanate: a highly reactive organic chemical containing one or more isocyanate (-N=C=O) groups. A basic component in SPF based systems and some polyurethane coating systems.


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