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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R-value: see Thermal resistance.

Racking: a method of asphalt shingle application, also referred to as the straight-up method, whereby shingle courses are applied vertically, up the roof rather than laterally or across and up.

Rafter: one of a series of sloped structural members, that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads.

Raggle: a groove or slot, often cut in a masonry wall or other vertical surface adjoining a roof, for inserting an inset flashing component such as a reglet.

Rake: the sloped edge of a roof at or adjacent to the first or last rafter.

Rake-starter (Bleeder strip): starter-strip used along rake edges in conjunction with asphalt shingle roofing.

Re-cover: the addition of a new roof membrane or steep-slope roof covering over a major portion of an existing roof assembly. This process does not involve removal of the existing roofing.

Reflectivity: see Light reflectance. Reglet: a sheet metal receiver for the attachment of counterflashing. A reglet may be surface-mounted, inset into a raggle or embedded behind cladding.

Reinforced membrane: a roofing or waterproofing membrane that has been strengthened by the addition or incorporation of one or more reinforcing materials, including woven or non woven glass fibers, polyester mats or scrims, nylon, or polyethylene sheeting.

Relative humidity (RH): the ratio of the pressure of water vapor present in a given volume of air to the pressure of fully saturated water vapor at the same temperature, expressed as a percentage.

Release tape (or Strip): a plastic film or paper strip that is applied to the back of self-sealing shingles and other materials. The strip prevents the material from sticking together in the roll or bundle. With asphalt shingles, the strip need not be removed for application of the shingles.

Replacement: the practice of removing an existing roof system down to the roof deck and replacing it with a new roofing system.

Reroofing: the process of re-covering, or tearing-off and replacing an existing roof system.

Resin: component B in SPF. This component contains a catalyst, blowing agent, fire retardants, surfactants and polyol. It is mixed with the A component to form polyurethane.

Ridge: highest point on the roof, represented by a horizontal line where two roof areas intersect, running the length of the area.

Ridge cap: a material or covering applied over the ridge of a roof.

Ridge course: the last or top course of roofing materials, such as tile, roll roofing, shingles, etc., that covers the ridge and overlaps the intersecting field roofing.

Ridge vent: a ventilator located at the ridge that allows the escape of warm and/or moist air from the attic area or rafter cavity.

Ridging: see Buckle.

Roll materials: a general term applied to rolls of roofing felt, ply sheet, etc., which are typically furnished in rolls.

Roll roofing: coated felts, either smooth or mineral-surfaced.

Roof: (1) the cover of a building; (2) to cover with a roof.

Roof area divider: refer to area divider. Roof area expansion Joint: see expansion joint.

Roof assembly: an assembly of interacting roof components including the roof deck, vapor retarder (if present), insulation and roof covering.

Roof cement: see Asphalt roof cement or Coal tar roof cement.

Roof covering: the exterior roof cover or skin of the roof assembly, consisting of membrane, panels, sheets, shingles, tiles, etc.

Roof curb: raised frame used to mount mechanical units (such as air conditioning or exhaust fans), skylights, etc. on a roof.

Roof jack: a metal or wood bracket used to support toe-boards on steep-slope roofs. (also see Flashing Collar.) Roof overhang: a roof extension beyond the exterior wall of a building.

Roof seamer: (1) machine that crimps neighboring metal roof panels together; (2) machine that welds laps of membrane sheets together using heat, solvent, or dielectric energy.

Roof slope: the angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as run). For English units of measurement, when dimensions are given in inches, slope may be expressed as a ratio of rise to run, such as 4:12 or as an angle.

Roof system: a system of interacting roof components, generally consisting of a membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building’s thermal resistance.

Rosin paper (specifically Rosin-sized sheathing paper): a nonasphaltic paper used as a sheathing paper or slip sheet in some roof systems.

Rubber: a material that is capable of recovering from large deformations quickly and forcibly. Run: horizontal dimension of a slope.