Term Description
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; requires placing a part of a shingle under product already in place every other course, which may result in a less-than-recommended number of nails being used for fastening.
Radiant barrier

A low emittance (0.1 or less) surface used in the construction of a radiant barrier system.
Radiant barrier system

A building construction consisting of a radiant barrier bounded by an open airspace.
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 or secondary horizontal structural members, such as purlins and the 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.
RCMA

Roof Coatings Manufacturers Association.
Re-covering

The process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering.

Receiver

A component in a two-piece counterflashing that may be surface-mounted to a wall, inset into a raggle or embedded behind cladding. It is used for ease of installation and future maintenance and repair or replacement. See "reglet."

Reflectance

Solar reflectance is the fraction of the solar energy (flux) that is reflected by the surface; reflectance is expressed as a percentage or a decimal value between 0.00 and 1.00.
Reflectivity

Defined as the reflectance of an opaque, optically flat surface or coating of thickness sufficient to be a completely opaque. "Reflectivity" is a property of a material, while "reflectance" is a property of a sample of the material.

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 roof or waterproofing membrane that has been strengthened by the addition or incorporation of one or more reinforcing materials, including woven or nonwoven glass fibers, polyester mats or scrims, nylon or polyethylene sheeting.
Relative humidity (RH)

The ratio of the partial pressure of water vapor in an air-vapor mixture to the maximum—or saturated— water vapor pressure at the same temperature, expressed as a percentage.
Replacement

The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering; also known as "tear-off and replacement."
Reroofing

The process of re-covering or tearing off and replacing an existing roof covering. See "re-covering" and "replacement."
Resin

(1) In spray polyurethane foam roofing, the B-component (B-side). This component contains a catalyst, blowing agent, fire retardants, surfactants and polyol. It is mixed with the A-component (A-side) to form polyurethane; (2) in plastics manufacturing, any polymer that is a basic material for plastics; (3) in grouting, a material that usually constitutes the base of an organic grout system.
Retrofit

The modification of an existing building or facility to include new systems or components.
Ridge

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

A horizontal board in wood frame construction at the upper end of the common rafters to which the rafters are nailed.
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 or shingles, 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., that are typically furnished in rolls.

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