(1) That part of any wall entirely above the roof; (2) That part of a perimeter wall immediately adjacent to the roof which extends above the roof.

A roofing assembly in which the membrane has been "spot affixed" to a substrate, usually with an adhesive or a mechanical device.

Powdered mineral (talc, mica, and so forth) placed on coated felts to prevent adhesion of concentric felt layers in the roll (sometimes called a releasing agent or antistick compound.

SI unit of measure for force per unit area.

The average force (or force per unit width) required to peel a membrane or other material form the substrate to which it has been bonded.

(1) Any object passing through the roof; (2) The consistency (hardness) of a bituminous material expressed as the distance, in tenths of a millimeter (0.01 mm), that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time and temperature.

An enclosed, unoccupied structure above the roof of a building, other than a tank, tower, spire, dome cupola or bulkhead, occupying not more than one-third of the roof area.

In tensile testing, the increase in the gauge length of a specimen measured at or after fracture of the specimen within the gauge length. Usually expressed as a percentage of the original gauge length.

An aggregate used in lightweight insulating concrete and in preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.

A unit of water vapor transmission defined as 1 grain of water vapor per square foot per hour per inch of mercury pressure differences (1" of mercury = 0.49 psi). The formula for perm is: P = Grains of Water Vapor/Square Foot x Hour x Inch Mercury (P = grain in/ft_h in Hg[P = ng/(Pa s m)]). See PERMEANCE.

(1) The capacity of a porous material to conduct or transmit fluids; (2) The amount of a fluid moving through a barrier in a unit time, unit area and unit pressure gradient not normalized for, but directly related to thickness.

(1) An index of a material's resistance to water vapor transmission; (2) The rate of water vapor transmission per unit area at a steady state through a material, membrane or assembly, expressed in Grain/Square Foot Hour Inch Mercury (grain/ft_h in Hg [ng/Pa a m_]). See PERM.

(1) The installation of a roof system or waterproofing system during two or more separate time intervals; (2) Applying the felt of plies of a built-up roof or waterproofing membrane in two or more operations, separated by a delay normally of at least one day; (3) The installation of separate roof system or waterproofing system component(s) during two or more separate time intervals. Application of surfacings at different time intervals are typically not considered phased application. See ONE-ON-ONE and SURFACING.

Polyisobutylene.

(1) A rectangular pattern of ridges in a roof membrane over insulation or deck joints; (2) A square or rectangle pattern of buckles or ridges in a roof covering generally coinciding with insulation or deck joints; generally, a function of movement of the substrate. See RIDGING.

Polyisocyanurate Insulation Manufacturers Association

A tiny hole in a coating, film, foil, membrane or laminate.

Prefabricated flashing piece used to flash around circular pipe penetrations.

(1) Tar derived from the destructive distillation of coal during the conversion of coal into coke; (2) A dark brown to black, semi-solid hydrocarbon obtained as residue from the partial evaporation or distillation of coal tar; (3) The slope of a roof expressed either in percent or in the number of vertical units of rise per horizontal unit of run; (4) The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet. See COAL-TAR, INCLINE, ROOF SLOPE and SLOPE.

(1) A flanged, open-bottomed, metal container placed around columns or other roof penetrations that is filled with hot bitumen and/or flashing or plastic cement to seal the joint. The use of pitch pockets is not recommended by NRCA; (2) A flanged, open bottomed enclosure made of sheet metal or other material, placed around a penetration through the roof, filled with grout an bituminous or polymeric sealants to seal the area around the penetration.

(1) Trowelable, plastic mixture of bitumen and asbestos (or other inorganic) stabilizing fibers and a solvent, used mainly for horizontal surfaces as opposed to flashing cement, which is designed for vertical surfaces requiring sag resistance; (2) A roofing industry generic term used to describe Type I asphalt roof cement that is a trowelable mixture of solvent based bitumen, mineral stabilizers, other fibers and/or fillers. Generally, intended for use on relatively low slopes not vertical surfaces. See ASPHALT ROOF CEMENT and FLASHING CEMENT.

A flexile sheet made by the extrusion of thermoplastic resins.

(1) An organic compound added to a polymer for the purpose of facilitating, processing and increasing the flexibility and toughness of the finished product; (2) High-boiling-point solvent or softening agent added to a polymer to facilitate processing or increase flexibility or toughness in the manufactured material; (3) A material, frequently solvent like, incorporated in a plastic or a rubber to increase its ease of workability, flexibility or extensibility.

A plastic-like polymer consisting of any of various complex organic compounds produced by polymerization which are capable of being molded, extruded or cast into various shapes or films. Generally they are thermo plastic in nature, i.e., they will soften when heated and harden when molded.

The material property of being flexible or moldable.

(1) A single layer of thickness of roofing material in a roofing membrane; (2) A layer of felt, ply sheet or reinforcement in a roof membrane or roof system; (3) A layer of felt in a built-up roof membrane system. A four-ply membrane system has four plies of felt at any vertical cross section cut through the membrane. The dimension of the exposed surface (the "exposure") of any ply may be computed by dividing the felt width (minus 2" by the number of plies; thus, the exposed surface of 36" wide felt in a four-ply membrane should be 8 1/2". See EXPOSURE.

Protected Membrane Roof

The mass in pounds of 480 square feet of dry, unsaturated felt. See FELT MILL REAM.

A cured, synthetic rubber sheet. Neoprene is the generic name
for polymers of chloroprene. See NEOPRENE.

(1) A group of synthetic resins which are normally cross-linked (cured) and made into a variety of elastomers; (2) A thermoplastic polymeric resin that is used to make a variety of materials and products. Polyester fibers are widely used as the reinforcing medium in certain membranes. See POLYESTER FIBER.

A synthetic fiber usually formed by extrusion. Nonwoven fabrics, mats and scrims made of polyester fiber are used for membrane reinforcement.

(1) A synthetic classified as an uncured elastomer composed of isoprene, highly-molecular isobutylene, carbon black and aging protectors; (2) A natural or synthetic chemical compound of high molecular weight or a mixture of such compounds, formed when monomers (small individual molecules) are combined to from large long-chain molecule; (3) A product formed by the polymerization of isobutylene. May be compounded for use as a roof membrane material.

(1) Long, chain macromolecules produced from monomers, for the purpose of increasing tensile strength of sheets used as membranes or flashing; (2) A natural or synthetic chemical compound of high molecular weight or a mixture of such compounds, formed when monomers (small individual molecules) are combined to form large long-chain molecules.

The process where monomers are combined to form large, chainlike molecules.

See MODIFIED BITUMEN.

A tough, lightweight plastic made by the polymerization of high purity propylene gas

Any of various thermoplastic or thermosetting resins, widely varying in flexibility and used on tough, chemical resistant coatings, adhesives, foams and electrical insulation.

(1) A polymer synthesized from vinyl chloride. It is thermoplastic in nature and has plasticizers added to impart flexibility; (2) Thermoplastic polymer, formulated with a plasticizer, used as a single ply sheet membrane material or liquid coating; (3) A synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers and other modifiers; rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.

A roof surface that is incompletely drained.

The excessive accumulation of water at low-lying areas on a roof.

(1) The drainage condition in which consideration has been made for all loading deflections of the deck, and additional roof slope has been provided to ensure complete drainage of the roof area within 48 or 24 hours of rainfall precipitation; (2) The drainage condition in which consideration has been made during design for all loading deflections of the deck, and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of rainfall, during ambient drying conditions.

A type of sealant often supplied in two parts, and used at difficult-to-flash penetrations, typically in conjunction with pitch pockets to form a seal.

A machine used in cold-forming sheet metal or strips of metal into desired profiled.

Concrete in which the reinforcing cables, wires or rods in the concrete are tensioned before there is load on the member, holding the concrete in compression for greater strength.

(1) A thin, liquid bituminous solvent applied to seal a surface, absorb dust, and improve the adhesion of subsequent applications of bitumen; (2) A thin, liquid-applied solvent-based bitumen that may be applied to a surface to improve the adhesion of subsequent applications of bitumen; (3) A material which is sometimes used in the process of seaming single-ply membranes to prepare the surfaces and increase the strength (in shear and pee) of the field splice.

(1) A roofing membrane with insulation and protective surfacing or ballasting on top; also called inverted or upside down roof; (2) An insulated and ballasted roofing assembly, in which the insulation and ballast are applied on top of the membrane (sometimes referred to as an "inverted roof assembly").

Force per unit area expressed in pounds per square foot. (Note: 1 sq. ft. = 144 sq. in.)

Force per unit area expressed in pounds per square inch.

Pint

The ability of the membrane to resist normally expected concentrated forces such as foot traffic and wheel loads.

Extent to which a material is able to withstand the action of a sharp object without perforation.

Horizontal secondary structural member that transfers loads from the primary structural framing.

(1) A polymer synthesized from vinyl chloride. It is thermoplastic in nature and has plasticizers added to impart flexibility; (2) Thermoplastic polymer, formulated with a plasticizer, used as a single ply sheet membrane material or liquid coating. See POLYVINYL CHLORIDE.