This glossary contains many useful terms and definitions that will help you understand much of the work we do at ROOFCORP.

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ICBO: International Conference of Building Officials.

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.

Ice dam protection membrane: a continuous membrane installed under steep slope roofing materials in areas subject to ice damming that prohibits water which gets through the roof covering from getting into the structure. Must also seal the fasteners that penetrates it.

Ignition temperature: the lowest temperature at which combustion will occur spontaneously under specific conditions.

Impact resistance: resistance to fracture under the sudden application of an exerted force.

Impregnate: In roofing materials manufacture, to completely surround the fibers in a felt or mat with bitumen, with the spaces between the fibers partially or completely filled without a continuous coating of bitumen on the surface.

Infrared thermography: The process of displaying variations of apparent temperatures (variation of temperature or emissivity or both) over the surface of an object by measuring variations in infrared radiance.

Inorganic: being or composed of materials other than hydrocarbons and their derivatives, or matter that is not of plant or animal origin.

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

In-service R-value: thermal resistance value established under installed conditions and measured over the expected service life of the material.

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 wind-driven precipitation. Typically used with wood shakes.

Interlocking shingles: individual shingles that mechanically attach to each other to provide enhanced wind resistance without reliance on sealing strips.

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 Styro-foam are registered trademarks of the Dow Chemical Company.

ISANTA: International Staple, Nail & Tool Association Isocyanate: a highly reactive organic chemical containing one or more isocyanate (-N=C=0) groups. A basic component in SPF based systems and some polyurethane coating systems. Isolation sheet: refer to slip sheet.

Joist: any of the small timbers, metal or wood beams arranged parallel to each other and spanning from wall to wall to support a floor, ceiling, or roof of a building.

Joule: a unit of energy or work; equals the work done by a force of 1 newton which acts over a distance of 1 meter in the direction of the force.

k or k-Value: thermal conductivity; the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient. In English (inch-pound) units of measurement, it is the number of BTUS that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in 1 hour with a temperature difference between the two surfaces of 1° F. It is expressed as Btu·inch/h·ft2·°F.

Kerf: (1) a slit or notch made by a saw or cutting torch; (2) the width of cut made by a saw or cutting torch.

Kesternich test: simulates acid rain conditions by subjecting test specimens to a sulfur dioxide atmosphere as well as condensing moisture for the purpose of evaluating rust/corrosion characteristics.

Knee cap: a metal cover trim that fits over a panel rib after it has been cut and bent.

Knee joints: see Knuckle.

Knuckle: a metal closure, either shop-or pre-fabricated, installed over the cut seam of a continuous metal roof panel at the transition from a steep-slope roof to a vertical roof or wall.

Laitance: a weak layer of cement and aggregate fines on a concrete surface that is usually caused by an overwet mixture, overworking the mixture, improper or excessive finishing or combination thereof.

Laminate: to join layers of materials together using fusion; the process of joining layers of materials together using adhesion.

Laminated shingles: see Dimensional shingles or Architectural shingles.

Lap: that part of a roofing, waterproofing, or flashing component that overlaps or covers any portion of the same or another type of adjacent component.

Lap cement: an asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing.

Lap seam: occurs where overlapping materials are seamed, sealed or otherwise bonded.

Latex: a stable dispersion of polymeric substance in an essentially aqueous medium.

Lead: a soft malleable, heavy metal; has low melting point and a high coefficient of thermal expansion.

Leader head: see Conductor head.

Lift: the sprayed polyurethane foam that results from a pass. It usually is associated with a certain pass thickness and has a bottom layer, center mass and top skin in its makeup.

Liquid-applied: application of bituminous cements, adhesives or coatings installed at ambient or slightly elevated temperatures.

Liquid-applied built-up roof: a continuous, semi-flexible roof membrane, consisting of multiple plies of felts, mats or fabrics laminated together with alternate layers of roof cements and surfaced with a liquid -applied coating with or without aggregate surfacing.

Live loads: temporary loads that the roof structure must be designed to support, as required by governing building codes. Live loads are generally moving and/or dynamic or environmental, (e.g., people, installation equipment, snow, ice or rain, etc.).

Loose-laid membrane: a ballasted roofing membrane that is attached to the substrate only at the edges and penetrations through the roof.

Low-slope roofs: a category of roofs that generally include weatherproof membrane types of roof systems in-stalled on slopes at or less than 3:12 (14 degrees).

Low temperature flexibility: the ability of a membrane or other material to resist cracking when flexed after it has been cooled to a low temperature.