26 September 2006
Cellular Polyisocyanurate Thermal Insulation Board; a thermal insulation similar in
appearance to polyurethane foam, but with improved fine resistance or rating.
Polymer. A macromolecular material formed by the chemical combination of
monomers having either the same or different chemical composition. Plastics, rubbers,
and textile fibers are all high molecular weight polymers.
Polyvinyl Chloride (PVC). A synthetic thermoplastic polymer prepared from
vinylchloride. PVC can be compounded into flexible and rigid forms through the use of
plasticizers, stabilizers, filler, and other modifiers; rigid forms used in pipes; flexible
forms used in manufacture of sheeting.
Ponding. Water in low or irregular roof areas that remains longer than 48 hours after
the cessation of rainfall, under conditions conducive to evaporation.
Preventive Maintenance. The regular, scheduled, inspection for and the repair of
normal, expected breakdown of materials and equipment.
Prime coat. First liquid coat applied in a multiple coat system.
Primer (bituminous). A thin liquid bitumen applied to a surface to improve the
adhesion of heavier applications of bitumen and to absorb dust.
Protected Membrane Roof (PMR). Roof assembly with insulation on top of membrane
instead of vice versa, as in conventional roof assembly (also known as inverted or
upside-down roof assembly).
Puncture Resistance. Index
of a material's ability
to withstand the action
of a sharp
object without perforation.
R-Factor. Resistance to heat flow. The summation of individual thermal resistances in
Rake. The sloped edge of a roof at the first or last rafter.
Rake trim. A flashing designed to close the opening between the roof and endwall
Re-covering. The process of covering an existing roof system with a new roof.
Reglet. A groove in a wall or other surface adjoining a roof surface for the insertion and
attachment of counterflashing.
Relative Humidity. The ratio of the mass per unit volume (or partial pressure) of water
vapor in an air-vapor mixture to the saturated mass per unit volume (or partial pressure)
of the water vapor at the same temperature, expressed as a percentage.
Replacement. The removal of all roof system components down to the structural deck
followed by installation of a completely new roofing system.