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Under One Roof

Canadian Roofing Reference Manual



A-frame: a portable frame built in the shape of a letter “A” and used by roofers to hoist materials.

Absorption: the ability of a porous solid material to hold within its body relatively large quantities of gases or liquids.

Active metal (anodic): a metal or material that readily gives up electrons to a cathodic (noble) material. See anodic. An active metal will corrode in the presence of moisture when in contact with a cathodic metal

Adhere: to cause two surfaces to be held together by the combined strength of the molecular forces and the mechanical interlocking achieved between adhesive and the bonded surface. See adhesion.

Adhesion: 1. The degree of attachment between two surfaces held together by interfacial forces – mechanical or chemical or both: 2. The degrees of attachment or bonding between application of the same substance. 3. The combined ultimate strength of the molecular forces and the mechanical interlocking achieved between the adhesive and the surface bonded. Adhesion is measure in shear and peel modes.

Adhesive: A cementing substance that produces a steady and firm attachment or adhesion between two surfaces. Adhesion is measured in shear and peel modes.

Aggregate: 1. Crushed stone, crushed slag, or water-worn or natural gravel used as protective surfacing or ballast in a roof system. 2. Any granular mineral material. 3. Roofing gravel in built-up roofing (BUR).

Aggregate, lightweight (LWA): Aggregate of low density; examples include coal bottom ash, pumice, scoria, volcanic cinders, tuff and diatomite; expanded or sintered clay, shale, slate, diatomaceous shale, perlite, vermiculite or slag and bonded or sintered coal combustion products (CCPs) used to produce lightweight concrete or component products.

Air barrier: An assembly of materials or building element used in building construction that provides resistance to the movement of air into and out of the building.

Air leakage: The movement of air through spaces between constituent parts of a roof system or other enclosure elements as a result of air pressure differences between one and the other side.

Air space: A cavity or unfilled space between two constituent parts in a roof system or other enclosure element of a building.

Alligatoring: Hardening and shrinking of exposed bitumen coatings due to oxidation, that produces small islands of bitumen between deep cracks and gives the appearance of alligator hide.

Aluminized steel: Sheet steel with a thin aluminum coating bonded to the surface to enhance weathering characteristics.

Aluminum: A non-rusting, malleable metal sometimes used for metal roofing and flashing.

Alloys, polymeric: A blend of two or more polymers, e.g. a rubber and a plastic, to improve properties such as impact strength.

Ambient temperature: The temperature of the air existing on all sides; air temperature.

Anodic: A metal or material that readily gives up electrons to a cathodic material in the presence of an electrolyte (see galvanic cell, galvanic series, and cathodic). As a result, the anodic material oxidizes to protect the cathodic material from corrosion.

Apex: The point, tip or summit of anything, the highest point of any roof or structure.

Application: The act of putting on or building up the felts and flashings of all elements of any roofing system. The materials may be hot or cold fluids or adhesives or prefabricated sheets.

Application rate: The quantity (mass, volume or thickness) of material applied per unit area.

Application temperature: The temperature of the hot materials such as asphalt when applied to the roof. See also equiviscous temperature (EVT).

Apron flashing: A term used for a flashing located at the juncture of the top of a sloped roof and a vertical wall, chimney or steeper-sloped roof.

Arch: A curved or pointed structural member which is supported at the sides or ends, to cover with a curved structure or to form a bent top or covering.

Architect: A person technically qualified and professionally licensed to practice architecture; that is designing and administering the construction of buildings.

Architectural panel: A metal roof panel; usually requires solid decking underneath and relies on slope to shed water.

Architectural shingle: An asphalt shingle that provides a dimensional appearance. See dimensional shingle.

Architecture: the art of science of designed buildings, the style of a building.

Area divider: A raised, flashed assembly, typically fabricated of dimensional wood components anchored to the roof deck that is used to separate large roof areas, roof assemblies composed of different/incompatible materials, or at changes in structural direction or deck types.

Asbestos: A group of natural, fibrous impure silicate materials.

Asphalt: A bituminous brown to black material derived from the distilling of crude oil, commonly left as a residue after evaporating or otherwise processing crude oil or petroleum. See bitumen.

Asphalt may be further refined to provide a wide range of viscosities and softening points required for this end use e.g. shingles, BUR for different slopes etc as per the following grade specifications:

  • Type 1: asphalt for use on built-up roofs with slopes less than or equal to 1:16 (6.25⁰) and for use as waterproofing below ground level when not exposed to surface temperatures above 25°C (77°F).
  • Type 2: asphalt for use on built-up roofs with slopes less than or equal to 1:8 (12.5⁰) and for use as waterproofing above ground level on vertical surfaces not exposed to direct sunlight.
  • Type 3: asphalt for use on built-up roofs with slopes greater than 1:8 (12.5⁰) for exposed applications or for use as waterproofing above ground level on vertical surfaces not exposed to direct sunlight.

Asphalt, air blown: Asphalt produced by blowing air through molten asphalt at an elevated temperature to raise its softening point and modify other properties.

Asphalt emulsion: A mixture of asphalt particles and emulsifying agent, such as bentonite clay or soap, and water.

Asphalt felt: An asphalt-saturated and/or asphalt-coated organic or inorganic felt. See also felt.

Asphalt mastic: A mixture of asphaltic material and graded mineral aggregate that can be poured when heated, but requires mechanical manipulation to apply.

Asphalt primer: See primer.

Asphalt roof cement: A trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers.

Asphalt shingle: A shingle manufactured by coating a reinforcing material (paper felt or fibreglass mat) with an asphalt-based coating and having mineral granules on the side exposed to the weather. See shingle.

Atactic: A chain of molecules in which the position of the side methyl groups is more or less random as in atactic polypropylene, APP.

Atactic polypropylene (APP): High-molecular-weight polymer formed by the polymerization of propylene and characterized by random arrangement of the side methyl groups around the chain backbone.

Attic: The cavity or open space above the ceiling and immediately under the roof deck of a building.


Backfill: Soil used to fill in a structure after the waterproofing or dampproofing and foundation work are completed: provides a slope for drainage away from the foundation.

Backing: Lumber placed behind or between other members to give support and strength.

Back mopping: Mopping the back or underside of the roofing material.

Backnailing: The practice of nailing the concealed portion of a roofing ply, steep roofing unit or other components in a manner such that the fasteners are covered by the next ply, or course and are not exposed to the weather in the finished roofing system. Hot-mopped roofing felts and polymer-modified bitumen sheets may be backnailed to prevent slippage. Also referred to as blindnailing.

Backrolling: Rolling a coating by hand, normally behind the spray or power roller applicator, to ensure better coverage and adhesion.

Backup plate: A rigid plate to support an end lap to provide uniform compression.

Bald roof: See smooth-surface roofing

Ballast: Crushed rock, gravel or pavers placed on loosely laid roofing membrane systems or roof insulation boards to hold them down from wind uplift, as in the case of an inverted roof (protected membrane roof assembly, PMR).

Base flashing: The extension of the roofing membrane over the cant and up the vertical surface.

Base sheet: A heavy sheet of saturated, coating or impregnated felt placed as the bottom or first ply in built-up or modified bitumen roofing membrane systems. Also called base ply.

Batch lot: All material of the same type defined by a complete cycle of production or manufacture.

Beam: A long piece of timber or iron used to support the rafters of a building; a horizontal timber or support.

Bevel: To give a sloping edge, to slant or incline (T bevel; a tool used to test accuracy of beveled edges).

Bind: To cause to stick together.

Bird Bath: Random, inconsequential amounts of residual water on a roof membrane.

Bitumen: A generic term applied to mixtures of predominantly hydrocarbons in viscous or solid form, derived from coal or petroleum. The roofing industry uses it to describe either coal tar pitch or asphalt and used as an adhesive and waterproofing agent.

Bituminous emulsion: 1. A suspension of minute globules of bituminous material in water of in an aqueous solution. 2. A suspension of minute globules of water or of an aqueous solution in a liquid bituminous material (invert emulsion).

Blast-furnace slag: See slag

Bleeding: The draining or loosening of saturants from the roofing material.

Blind nailing: Application of roofing in such a manner as to cover all nails heads by overlapping material.

Blister: An enclosed raised spot or area containing gas or liquid that shows on the surface of prepared and built-up roofing. Small blisters confined to the surface are called weather blisters, rash blisters, pimpling or blueberries. The larger, more serious and usually more evident blisters are structural blisters. These blisters are spongy to the touch and may occur between any of the layers of roofing felt or between membrane and deck or insulation.

Block copolymer: An essentially linear copolymer in which there are repeated sequences of polymeric segments of different chemical structure, e.g. styrene – butadiene – styrene (SBS), which is commonly used as a modifier in bitumen.

Blocking: 1. Wood built into a roofing system above the deck and below the membrane and flashing to (a) stiffen the deck around the opening (b) act as a stop of insulation, (c) serve as a nailer for attachment of the membrane or flashing. 2. Wood cross-members installed between rafters or joists to provide support at cross-joints between deck panels. 3. Cohesion or adhesion between similar or dissimilar materials in roll or sheet form that may interfere with the satisfactory and efficient use of the material.

Blueberry: A small bubble found in the flood coat of an aggregate-surfaced built-up roof. (See blister)

Board/block insulation: Rigid insulation preformed into rectangular units having a degree of suppleness. The boards may be of homogeneous material or of composite construction.

Bond: 1. To hold together tow roofing components by means of an adhesive. 2. The adhesive strength that prevents delamination of two roofing components. 3. A guarantee relating to roofing performance.

Bonding adhesive: the adhesive required to adhere a single ply membrane to its substrate.

Boot: A bellows-type covering to exclude dust, dirt, moisture, etc, from a flexible joint. It is used for making a watertight joint around a roof penetration.

Brace: A piece of wood or other material that holds anything tightly or supports it firmly; a prop.

Brooming: Embedding a ply by using a broom to smooth it out and ensure contact and adhesion with the underlying substrate.

Buckle: Large elongated bulge or fold in a roofing membrane as a result of separation from the substrate accompanied by expansion or stretching.

Building Code: Governmental rules and regulations for building.

Built-up Roofing (BUR): A continuous, semi-flexible membrane consisting of plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggregate, or coating for protection from solar radiation. May include modified bitumen membrane system of more than one ply.

Burner: An apparatus that emits flame used to heat a kettle or to dry off roofs.

Butt: Short length of material; the unused end portion of a roll of roofing material.

Butt Joint: A joint formed by adjacent, separate sections of material, such as where two neighbouring pieces of insulation abut.

Butter: To smooth on plastic with a trowel.

Butt joining: Two pieces of roofing material fitted squarely against each other without overlapping.

Butyl rubber: A synthetic rubber based on isobutylene and minor amount of isoprene.


Cable: A heavy rope of chain.

Cant strip: A triangular strip of wood or fiberboard that forms a beveled transition for membranes that is placed at the intersection of a roof deck with a higher wall or other vertical surface. The roofing membrane and flashing are eased through the change in direction from essentially horizontal to vertical along it 45 degree sloping surface.

Cap flashing: Any material, usually sheet metal, covering the top of a wall or parapet, designed to shed water.

Cap sheet: 1. The top ply of a built-up roofing membrane acting as the finished surface of a roof. 2. Any mineral-surfaced or other coated felt or sheet designed to provide waterproofing and weatherability. 3. The finishing layer in a modified bitumen roof membrane system.

Caulking: Any of a wide range of bituminous, rubber, plastic or other materials suitable for filling seams or cracks to make them tight against water leakage and remain plastic for an extended time after application. See also sealant.

Caulking cement: Any of a wide range of weather-resistant plastic cements suitable for caulking in any roofing application or roofing maintenance. See also plastic cement.

Cement: A substance used to make objects adhere to each other. In the roofing industry loosely applied to mean caulking and mastic.

CGSB: Canadian General Standards Board.

Chalking: A powdery residue on the surface of a material resulting from degradation or migration of an ingredient or both.

Chalk line: Heavy string or cord used for lining purposes.

Channel mopping: See strip mopping.

Chlorinated polyethylene (CPE): Family of polymers produced by chemical reaction of chlorine on the linear backbone chair of polyethylene. The resultant rubbery thermoplastic elastomers presently contain 25 to 45% chlorine by weight and 0 to 25% crystallinity, CPE can be vulcanized but is usually used in a non-vulcanized form.

Chlorosulfonated polyethylene (CSPE): Family of polymers that are produced by polyethylene reacting with chlorine and sulfur dioxide. Present polymers contains 25 to 43% chlorine and 1.0 to 1.4% sulfur. They are used in both vulcanized and non-vulcanized forms. Most membranes based on CSPE are non-vulcanized.

Cleat: A strip of wood or metal fastened across other materials for additional strength; may be nailed against the wall for supporting an object.

Coal tar: Tar derived from the destructive distillation of coal during the conversion of coal into coke.

Coal tar felt: A felt that has been saturated with refined coal tar.

Coal tar pitch: A bituminous material from the heavy end of the distillation of crude coal tar produced from the coking of coal.

Coated fabric: 1. Fabric that has been impregnated and/or coated with a plastic material in the form of a solution, dispersion, hotmelt or powder. 2. Also applies to materials resulting from the application of a preformed film to a fabric by means of calendering.

Coated base sheet: 1. An asphalt felt coated on one or both sides with harder, more viscous asphalt and surfaced with mineral matter of various sizes. 2. A glass fibre felt that has been simultaneously impregnated and coated with asphalt on both sides. These products come under the group of roll roofing.

Coating: A thin layer of a substance used to cover other materials, to provide an aesthetic or protective function.

Cold process roofing: A continuous, semi-flexible membrane consisting of plies of felts, mats, or fabrics laminated on a roof with alternate layers of roof cement and surfaced with a cold-applied coating.

Collar: A metal cap flashing around a vent pipe projecting above a roof deck.

Compatible materials: Two or more materials or substrates that can be mixed, blended or attached without separating, reacting or affecting the materials adversely.

Competent worker: In relation to specific work, means a worker who,

  1. is qualified because of knowledge, training and experience to perform the work,
  2. is familiar with the Occupational Health and Safety Act and with the provisions of the regulations that apply to the work, and
  3. has knowledge of all potential or actual danger to health or safety in the work;

Compound: An intimate admixture of a polymer with all the ingredients necessary for the properties required of the final product.

Compression: The decrease in length produced in a test specimen during a creep test. This term commonly applies to insulation boards or blocks.

Concealed nailing: See blind nailing.

Condensation: The change from water vapour to liquid water, resulting from a drop in temperature of an air vapour mixture.

Concealed Condensation: Condensation that occurs within a roofing system and is not seen.

Interstitial condensation: That which occurs in the interstices between constituent parts of a roof system. Same as concealed.

Surface Condensation: That which appears on the colder exposed surfaces of a roofing system.

Condense: To make denser or more compact, as when a material (e.g. water vapour) changes from its gas phase to its liquid phase.

Connection: The act or means of joining or uniting.

Control joints: An elevated roof element used to divide roof membrane areas, to control membrane movement.

Conventional roof assembly: A roofing assembly where the insulation s installed beneath the primary roof membrane.

Copolymer: A mixed polymer; the product of polymerization of two or more substances at the same time.

Counter flashing: The material, usually sheet metal, protecting the top edge and covering or partially covering the vertical membrane flashings, which may extend onto the roof.

Course: A continuous row or layer of shingles or other roofing materials.

Cover Board: Thin, normally homogeneous materials formed into boards and used over roof insulation to provide protection to the insulation during installation and service and to enhance the performance of the roofing assembly.

Coverage or Covering: 1. The area to be covered per unit volume of coating to obtain a specified dry thickness. 2. Area covered by a unit of roofing such as a bundle of shingles of a roll of roofing.

Crack: A break in a roofing membrane as a result of flexing, often at a ridge or wrinkle.

Cricket: A small false roof or an elevated part of the roof that is designed to channel surface water from behind an obstacle, such as a chimney, to drains. Frequently located in a valley, a cricket is often constructed like a small hip roof, or like a pyramid with a diamond shaped base. Also called a saddle.

Crowbar: A long heavy steel bar, pointed or wedge-shaped at the working end.

Crushed stone: The product resulting from the artificial crushing of rocks, boulders, or large cobblestones, substantially all faces of which have resulted from the crushing operation.

CSA: Canadian Standards Association.

Cupola: A hemispherical roof, a small structure above the roof.

Curb: A low wall of wood, masonry or metal built above the level of the roof, surrounding roof openings or supporting mechanical equipment.

Cured: Completed dry; moisture free.

Curing: To change the properties of a polymeric system into a more stable, usable condition by the use of heat, radiation, or reaction with chemical additives. See also cross linking and vulcanization.

Curling: An upward curled felt at sidelaps or endlaps. Also called flagged edge or sharkfin.

Cutback: A solution of bitumen in a volatile solvent used as a primer, cold-application cementing agent or roof coating. Filled cutbacks may contain mineral particles and inorganic fibres.

Cut-off: A material seal designed to prevent lateral water movement into the insulation where the membrane terminates at the end of a day’s work or to isolate sections of the roofing system. It is usually removed before the continuation of the work.

Cut-out: The open portions of a strip shingle between the tabs. Sometimes referred to as a keyway.


Dampproofing: The treatment of a building material or component surface with a bituminous or other coating to provide some measure of resistance to the passage of moisture into or through the material or components.

Dead load: The weight of a structure itself, including the weight of fixtures or equipment permanently attached to it.

Deck: The structural surface to which the roofing or waterproofing system is applied. See also Structural roof deck.

Deflection: 1. The downward displacement of a structural member or system under load. 2. The change in mid-span position of a test specimen during a creep test.

Degradation: A deleterious change in the chemical structure, physical properties or appearance of an organic material.

Delamination: 1. Separation of components within a system as a result of cohesive or adhesive failure. 2. Separation of the laminated layers of a component or system.

Design load: The total load on a structural system for the most severe combination of loads and forces which it is designed to sustain.

Detail: One of the many minor parts into which a building may be divided; a drawing of such a part.

Diagonal: Crossing obliquely as from corner to corner.

Diameter: A line through the center, as of a circle or sphere, terminated at the boundary thereof.

Dimensional stability: The degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity.

Dipper: A ladle for pouring bitumen.

Direction change: A change in the orientation of the principal dimension or of the support of adjoining units of the roofing system.

Dormer: A separate smaller roofed structure that projects from a sloping roof to provide more space below the roof and to accommodate a vertical window.

Double pour: The application of the top covering of bitumen and gravel surfacing of a built-up roof in two separate operations. A quantity of gravel is spread over a first-pour coat of bitumen, loose gravel is removed, and additional gravel is spread into a second-pour coat of bitumen.

Downspout: A pipe for conveying rain water from a roof gutter to a drain, or from a roof drain to a storm drain. (also called a conductor).

Drain: An outlet to allow water to flow from a surface into a drain pipe and away from the building through a drainage system.

Drainage layer: Component(s) that form part of a vegetative roof system assembly that allows for flow of water to a roof’s drainage points.

Drip edge: The formed edge on metal flashing used at the eaves or other roof details to encourage water to drip away from vertical surfaces of the building detail.

Dry sheathing: A felt or paper used in certain applications to prevent bitumen drippage or to act as a separation sheet between components.


Eave: The projecting lower edge of a roof. That part of a roof which projects beyond the wall.

Eaves flashing: The treatment of the edge of a roof with felt and metal flashing. The portion of the metal eaves flashing exposed on the elevation may be called a fascia flashing.

Eavestrough: A gutter along the eaves of a roof for carrying off rainwater.

Edge lap: The overlap of the edge of a ply over the previous ply. Also called side lap.

Edge venting: The practice of providing regularly spaced or continuous openings at a roof perimeter. Designed to relieve water vapour pressure and usually combined with venting channels in the insulation and stack venting towards the center of the roof.

Elasticity: The property of matter of immediately returning to its appropriate initial dimensions and shape after the removal of the stress that caused the deformation.

Elastomer: A macromolecular material that returns rapidly to its appropriate initial dimensions and shape, after substantial deformation by a low level of stress and the release of that stress.

Electronic leak detection (ELD): Non-destructive testing for the purpose of locating breaches in the waterproofing layer of a roof assembly by means of a leak sensor using low voltage electrical current. See also vector mapping.

Embedment or Embed: 1. The process of pressing a felt, aggregate, fabric, mat or panel uniformly and completely into hot bitumen or adhesive to ensure intimate contact at all points. 2. The process of pressing granules into coating in the manufacture of factory- prepared roofing, such as shingles, roll roofing.

Emulsified asphalt: Asphalt dispersed in water with or without a filler and held in suspension by means of an emulsifier. The asphalt particles cement together when the water evaporates.

Emulsion: An intimate mixture of bitumen and water, with uniform dispersion of the bitumen or water gobules, usually stabilized by an emulsifying agent or system. When the water evaporates the bitumen particles cement together.

End lap: The amount of overlap at the start of a roll of felt over the end of the previously laid roll.

Envelope: 1. The practice of carrying the air barrier/vapour retarder or other waterproofing sheet up and onto the top surface of the insulation in a compact roofing system. 2. A continuous membrane edge seal formed at the perimeter and at penetrations by folding the base sheet or ply over the plies above and securing it to the tip of the membrane. The envelope prevents bitumen seepage from the edge of the membrane.

Equiviscous temperature (EVT): The temperature at which bitumen will have the optimum viscosity for spreading at the required rate in roofing application.

Equiviscous temperature (EVT) application range: The recommended bitumen application temperature range. The range is approximately 14°C/25°F above or below the EVT, thus giving a range of approximately 28°C/50°F. The EVT range temperature is measured in the mop cart of mechanical spreader just prior to application of the bitumen to the substrate.

Equiviscous temperature (EVT) for asphalt: The recommended EVT for roofing asphalt as follows:

Mop application: The temperature at which the asphalt’s apparent viscosity is 0.125 Pa s (125 centipoise).

Mechanical spreader application: The temperature at which the asphalt’s apparent viscosity is 0.075 Pa s.

Ethylene Propylene Diene Monomer (EPDM): A synthetic elastomer based on ethylene, propylene and a small amount of a non-conjugated diene monomer to provide for vulcanization.

Expanded polystyrene (EPS): Insulation composed principally of polystyrene resin processed to form a rigid foam having a predominantly closed-cell structure. Boards or blocks are formed during expansion. See also insulation.

Expansion joint: A structural separation used to permit differential movement of a structure caused by expansion and contraction due to temperature change without damage to the roofing or waterproofing system. The joint is provided with a flexible watertight connection detail.

Exposed nailing: Application where the nail heads are exposed to the weather.

Exposure: 1. The time during which a portion of a roofing element is exposed to any environment; natural or laboratory created. 2. The transverse dimension of a roofing element not overlapped by an adjacent element in any roofing system. The exposure of any ply in a membrane may be computed by dividing the felt width minus 50 mm (2 in), by the number of shingled plies; thus, the exposure of a 900 mm (36 in) wide felt in a shingled, for ply membrane should be (900-5)/4 = 213 mm (8.5 in).

Extruded polystyrene (XPS): Insulation board produced by a continuous extrusion process as the resin foams. This forms a tight and complete skin on each side of the board.


Fabric: 1. Geotextile membranes used as a protective or separating layer in roofing and waterproofing systems. 2. A woven cloth of organic or inorganic filaments treated with bitumen and being stronger than felt, used in special flashing applications.

Fabric-reinforcement: A fabric or scrim used to add structural strength to a polymeric sheet of two or more plies. The sheeting is referred to as supported.

Fall: The vertical distance in millimetres through which a roof incline falls in a horizontal distance of one metre.

Fall arrest system: an assembly of components joined together so that when the assembly is connected to a fixed support, it is capable of arresting a worker’s fall.

Fall restricting system: a type of fall arrest system that has been designed to limit a worker’s fall to a specified distance.

Fascia: Any cover board at the edge or eaves of a flat or sloping overhanging roof.

Feather: To reduce the edge of a material to a very small dimension like a feather edge.

Felt: A general term used to describe sheet roofing material consisting of a mat of organic or inorganic fibres untreated, saturated, impregnated or saturated and coated with bitumen and supplied in roll form.

Felt layer: A piece of mobile mechanized roofing equipment used for spreading bitumen and laying felt in a single continuous operation.

Fibre: A tough substance that is separated into threads and spun or woven.

Fibreboard: A type of insulation composed principally of cellulose fibres usually derived from paper, paperboard stock or wood, with or without binders. See also insulation.

Fill: 1. Aggregate and cement mixtures placed on a roof deck in varying thicknesses to level out depressions and irregularities, or to form slopes to roof drains. 2. As used in textile technology, refers to the threads or yarns in a fabric running at right angles to the warp. Also called filler threads.

Filler: 1. Finely-divided mineral matter used as an extender to improve the properties of asphalt coatings for shingle and built-up roofing felts, and bituminous plastic cement or mastic. 2. Different types of fillers are used in some polymeric materials to improve some mechanical properties and also to reduce the cost of the finished product. See also stabilizer.

Filter fabric: a woven inorganic cloth or geotextile used as a filter that allows passage of water while preventing passage or migration of fines particles and soil in a protected membrane or vegetated roof system.

Fire Prevention Tape: A self-adhesive modified bitumen tape required to cover/seal substrate gaps, cracks and voids to prevent torch flame infiltration.

Fire resistance: The property of a material or assembly to withstand fire or give protection from it.

Fire retardant: A chemical used to impart flame resistance.

Fish mouth: 1. A half-cylindrical or half-conical opening formed by an edge wrinkle or adhesion failure. May be isolated occurrences or in a more or less regular pattern. 2. In shingles, a half-conical opening formed at a cut edge.

Fixed support: a permanent or temporary structure or a component of such a structure that can withstand all loads and forces the structure or component is intended to support or resist and is sufficient to protect a worker’s health and safety and includes equipment or devices that are securely fastened to the structure or component.

Flammability: Those characteristics of a material that pertain to its relative ease of ignition and ability to sustain combustion.

Flammable liquid: a liquid with a flash point below 37.8°C (100°F) and a vapour pressure not exceeding 275 kilopascals absolute at 37.8°C (100°F).

Flashing: A continuation of the roofing proper to cover any element of the roof structure departing from the roof deck incline.

Base Flashing: The extension of the roofing membrane over the cant and up the vertical surface

Cap Flashing: The covering, typically of sheet metal, covering the base flashing or capping a higher wall such as a parapet.

Counter Flashing: Similar to cap flashing, but sometimes used for the upper portion of the sheet metal flashing when the metal flashing is divided into two pieces.

Gravel Stop: A formed strip of material, usually metal, nailed around the edge of a graveled roof to prevent the gravel from rolling or washing off and to add a finished appearance to the roof. It may be combined with the fascia flashing.

Step Flashing: Individual pieces of flashing material used to flash the sides of chimneys and dormers, and similar projections on steeper sloping roofs usually shingled. The individual pieces are stepped up the slope.

Thru-wall Flashing: Flashing extending completely through a wall system to prevent water infiltration behind lower elements and provide drainage plane.

Flashing Cement: A trowel-able mixture of asphalt, volatile solvent and mineral fillers used as a cold coating in the application of flashing, for sealing around roofing details and for cold patching. Also called plastic cement.

Flash off: The time required for the volatiles in a petroleum-based adhesive/primer to escape into the atmosphere prior to bonding.

Flash point: The lowest temperature at which vapour from a combustible substrate will ignite when exposed to an ignition source but will not remain burning.

Fleece: Term used to describe mats or felts of usually non-woven fibres.

Flood coat: The top layer of bitumen for an aggregate-surfaced built-up roofing membrane, poured or flooded onto the finished felts and over which the aggregate is spread. Also called a pour coat.

Fluid-applied elastomer: An elastomeric material, which is fluid at ambient temperature and that dries or cures after application to form a continuous membrane for roofing and waterproofing.

Flush: A term applied to surfaces that are level and form a single unbroken surface.

Flux: A bituminous material used as a feed stock for further processing and as a material to soften other bituminous materials.

Factory Mutual Research Corporation (FMRC): A division of Factory Mutual which approves roofing products and systems for use in roofing based on their fire resistance, wind resistance and other physical and mechanical properties.

Freeze-thaw resistance: Resistance to cycles of freezing and thawing that could affect application, appearance or performance.

Full body harness: a device that can arrest an accidental vertical or near vertical fall of a worker and which can guide and distribute the impact forces of the fall by means of leg and shoulder strap supports and an upper dorsal suspension assembly which, after the arrest, will not by itself permit the release or further lowering of the worker.

Full mopping: Application to provide a continuous, reasonably uniform layer of bitumen over the entire surface being mopped. Also called solid mopping.


Gable end: The triangular end of an exterior wall from the level of the eaves to the ridge of a double-sloped roof which terminates at one or both ends in gable. A gable end is the end wall of a building with a gable formed by the roof.

Gable roof: A ridged or double-sloped roof that terminates at one or both ends in a gable.

Galvanic action: An electrochemical action that generates electrical current between two metals of dissimilar electrode potential.

Galvanic series: A list of metals and alloys arranged according to their relative electrolytic potentials in a given environment.

Galvanize: To coat steel or iron with zinc

Gauge: A metal thickness measurement.

Glass felt: 1. Felt made from glass fibres. 2. Glass fibres bonded into a sheet with resin and suitable for impregnation in the manufacture of bituminous waterproofing and roofing membranes and shingles.

Glass fibre: Random stacking of fibres to make insulator batt or board. The top of the batt is surfaced with kraft paper. The board is surfaced on both faces with fibre reinforced asphalt and kraft paper that provides a tough surface for mopping BUR or applying other roofing membranes.

Glass mat: A thin mat of glass fibres with or without a binder.

Glaze coat: A thin coating of bitumen applied to the felts of unfinished roofing to give short term protection from weather when roofing operations are delayed, or prior to the application of the protective surfacing.

Granules: Particles of a graded size that are embedded in the asphalt coating of shingles, mineral-surfaced roofing, and modified bituminous membranes. These granules are opaque, natural, ceramically-coloured aggregates or crushed slags. The slag granules have a glassy or glittery appearance.

Gravel: Small pieces of aggregate larger than sand grains resulting from the natural erosion or the crushing of rock, used to protect bituminous surfaces or ballast in roofing systems

Gravel in: To spread aggregate into hot bitumen on the surface of the roofing membrane.

Gravel spreader: A piece of mobile mechanical roofing equipment that dispenses and spreads gravel in one continuous operation.

Gravel stop: A formed strip of material, usually metal, designed to prevent loose aggregate from rolling or washing off the roof and to add a finished appearance to the roof.

Grout: A fluid cement mortar mixture used to fill joints and cavities of masonry or concrete building construction. On roof decks the joints between many types of precast roof deck slabs are grouted.

Growing medium: an engineered blend of organic and inorganic materials specifically designed for the growth of plants in a vegetative roof system.

Guardrail system: an assembly of components joined together to provide a barrier to prevent a worker from falling from the edge of a surface.

Gum box: A flanged, open bottomed metal container placed around a roof penetration and sealed into the primary membrane. A bitumen or polyurethane filler is installed to shed water and waterproof the penetration. Also known as a pitch pan/pocket.

Gutter: Trough at the eaves of a roof to convey rain water from the roof to a downspout.


Headlap: In shingle or other overlapped unit roofing, the amount that the head of an underlying unit is lapped or covered by the lower edge of the uppermost overlying unit at the location. For double-coverage units, the head lap is the unit width minus twice the exposure. See also exposure.

Heat seaming: The process of joining two or more thermoplastic films or sheets by heating areas in contact with each other to the temperature at which fusion occurs. The process is usually aided by a controlled pressure. In dielectric seaming, the heat is inducted within films by means of radio frequency waves.

Hip: The sloping line along the outer angle formed by the meeting of two sloping sides of a roof whose eaves meet at a right-angle. A hip roof is one that rises by inclined planes from all four sides of a building to form hips at the intersection of adjacent roof slopes.

Hip roof: A roof that rises by inclined planes to form one or more hips.

Hoist: A hoisting machine, to pullup.

Hood: A sheet-metal cover over equipment, stack vents or similar roof details.

Horizontal application: Modified bitumen or other roll roofing applied with the laps parallel to the eaves of a sloping roof.

Hydrostatic pressure: The pressure equivalent to that exerted on a surface by a column of water of a given height.


Ice dam: A mass of ice formed at the transition from a warm to a cold roof surface. Frequently formed by re-freezing meltwater at the overhang of a sloping roof, an ice dam may cause ice and water to back up and make the surface slippery for snow to slide down.

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

Incline: The angle made by a roof plane with a horizontal plane. Interchangeable with slow, fall, or pitch.

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

Insulation: A material used as part of a building enclosure to retard the flow of heat through the enclosure. It is made from a variety of organic and inorganic fibres and foams, e.g., expanded/extruded polystyrene, glass fibre, cellular glass, phenolic foam, perlite, polyurethane foam, polyisocynurate foam. It can be loose-filled, or used in batt, board or block form. See also roof insulation, board insulation.


Jack: A flanged metal sleeve used as part of the flashing around small items that penetrate a roof.

Jacket: A form of facing applied over insulation board.

Joist: One of a number of smaller closely-spaced parallel structural supports for a flat roof deck spanning between walls, roof beams, or purlins, or to support a flat ceiling below a sloping roof.


Kettle: Equipment used for heating bitumen to the temperatures required for application.

Kettle temperature: the temperature to which bitumen is heated in the roofing kettle, often considerably higher than that at the point of application.

Kettle thermometer: A thermometer used for checking the temperature of the heated bitumen in the kettle, often considerably higher than the temperature at the point of application.


Laminated shingles: See dimensional shingles or architectural shingles.

Lap: That part of a roofing unit that covers the preceding course in any overlapping roofing application. Applied to shingles, built-up roofing felts, and most other types of roofing. See also exposure.

Leader: Drain pipe, downspout or conductor. See conductor.

Lean-to: A sloping roof resting against a higher wall of a building.

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 fill insulation: Insulation in granular, nodular, fibrous, powdery, or similar form designed to be installed by pouring, blowing, or hand placement. See also insulation.

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

Low-sloped roof: A category of roofs that generally include weather proof membrane types installed on slopes at or less than 1 in 4 or 25%. So-called flat roof is now technically called low-slope, as it has a recommended minimum slope of 1 in 50 or 2%, for drainage purposes.


Mansard: A roof that rises by inclined planes from all four sides of a rectangular building. Each sloping roof has two inclines, the lower one usually very steep and the upper one almost flat.

Mastic: 1. A material of relatively viscous consistency that dries or cures to form a protective finish, suitable for application to thermal insulation in thickness greater than 0.75 mm per coat. 2. Trowelable bituminous paste made by adding mineral fillers to concentrated cutbacks. See also plastic cement, cement and asphalt mastic.

Membrane: A continuous sheet of material whether it is prefabricated as a flexible polymeric sheeting or is sprayed or coated in the field, in single ply or in multiple plies.

Membrane flashing: The vertical extension of the roofing membrane installed at horizontal to vertical junctions at roof penetrations and membrane terminations

Membrane protection: Inorganic boards or geotextile blankets that provide protection of the roof membrane from damage caused by foot and equipment traffic.

Metal flashing: Frequently used as through-the-wall, cap or counter-flashing.

Mil: A unit of measure, one mil is equal to 25.4 micrometres or 0.001 in. It is often used to indicate the thickness of a roofing membrane.

Mineral granules: See granules.

Mineral stabilizer: A fine, water-insoluble inorganic material, used in admixture with solid or semisolid bituminous materials.

Mineral-surfaced sheet: A felt that is coated on one or both sides with asphalt and surfaced with mineral granules.

Mini mopper: A small container with wheels that can be pushed along over the roof to dispense bitumen for the laying of roofing felts.

Modified bituminous membrane: 1. A bituminous material that has been chemically or physically altered by the addition of polymers intended to improve its performance characteristics. 2. Composite sheets consisting of a polymer modified bitumen often reinforced and sometimes surfaced with mineral granules or metal foils.

Mop: A tool used for the application of hot bitumen made from a bundle of cotton or other yarn attached to a long wooden handle. Bitumen soaked up and held by it when dipped into a container of hot material is transferred to and spread on the roof.

Mop-and-flop: An application procedure in which roofing elements (insulation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate locations, coated with adhesive, and then turned over and adhered to the substrate.

Mopping: 1. The act of spreading hot bitumen with a mop. 2. Also may refer to a layer of hot bitumen mopped between plies or over roofing felts.


Nailer: See nailing strips.

Nailing: Fastening of roofing materials by nails or other hammer-driven special fasteners.

Nailing strips: A member, usually of wood, set into or secured to non-nailable roof decks or walls to allow for positive anchorage by nailing of roofing felts, insulation or flashings.

Neoprene: A synthetic rubber (polychloroprene) applied in liquid or sheet form in roofing membranes or flashing.

Night seal (or night tie-in): A material and/or method used to temporarily seal a membrane edge during construction to protect the roofing assembly in place from water penetration. Usually removed when roofing application is resumed.

Nitrile rubber: A family of copolymers of butadiene and acrylonotrile that can be vulcanized into tough oil resistant compounds. Blends with PVC are used where ozone and weathering are important requirements in addition to its inherent oil and fuel resistance for roofing application.

Nondestructive testing (NDT): A method to evaluate the disposition, strength or composition of materials or systems without damaging the object under test. Typically used to evaluate moisture content in roofing assemblies, the three common test methods are electrical capacitance, infrared thermography and nuclear back-scatter.

Non-woven: A manufactured sheet, web or batt of directional or randomly oriented fibres of natural or man-made origin produced by physical, chemical and mechanical means. See also dry-laid, wet-laid, spunbonded, spunlaced and needle punched.

Nylon: Generic name for a family of polyamide polymers characterized by the presence of the amide group (CONH). Fibres are used as a scrim or fabric for reinforcing roofing sheets.


Organic: Being or composed of hydrocarbons or their derivatives, or matter of plant or animal origin.

Organic felt: Felt made from organic fibres and in particular wood fibres

Overhang: The part of a roof structure that extends beyond the exterior walls of a building.

Overheating: Heating the material in the kettle in such a manner that its characteristics are altered. This alteration could occur by prolonged heating at proper temperature or by heating for shorter periods at higher than recommended kettle temperature.


Parapet: The part of a perimeter wall that extends above the roof.

Parting agent: Fine sand, mica talc or similar material spread over the surface of roofing membranes to prevent sticking in the roll.

Penetration: A measure of the hardness related to viscosity of bitumen as determined by an empirical test that gives the depth of penetration of a standard weighted needle vertically into a sample after a definite time and at a particular temperature. It is measured as the distance of penetration in tenths of a millimetre. A cone is sometimes used for special purposes instead of a needle.

Perforated felt: Bitumen-saturated felt perforated with closely-spaced small holes to allow air and moisture to escape during application of BUR.

Perlite: 1. It is produced by heating and expanding silicaceous volcanic glass and is used as loose fill insulation. 2. It is also used as an aggregate in light-weight concrete. 3. It is combined with organic fibres and waterproofing binders to make insulating boards.

Permeability: 1. The capacity of a porous material to conduct or transmit fluids. 2. the time rate of vapour transmission through unit area of flat material of unit thickness induced by unit vapour pressure difference between two specific surfaces, under specified temperature and humidity conditions.

Phased application: The practice of laying one or more plies of a built-up roofing at one time with the additional plies laid at a later time.

Photovoltaic array (PV): An assembly of photovoltaic panels or modules together with support structure.

Photovoltaic cell: basic semiconductor device that converts radiant solar energy to direct current electricity.

Photovoltaic module: a single package of two or more interconnected photovoltaic cells that includes a frame or mounting points.

Photovoltaic panel: a number of modules that are electrically and mechanically connected and provides a field-installable unit.

Picture framing: 1. A rectangular pattern of ridges in a membrane over insulation or deck joints. 2. A pattern used in arranging strip fasteners.

Pinhole: A tiny hole in a film, foil, or laminate comparable in size or shape to one made by a pin.

Pitch: 1. A black or dark brown solid cementious residue that results from the distillation of tar. A tar derived from coal is referred to as coal tar, and a pitch derived from coal tar as coal tar pitch. Also called roofer’s pitch. 2. Incline or slope of roof.

Pitch pocket: A flanged, open-bottomed metal container placed around items such as columns that project through the roof system. The flange is properly set into the roof membrane and the pan is well filled with plastic cement or hot bitumen. Also called mastic pan, plastic pan, gum box.

Plank deck: Wood deck of planks usually 38 mm to 90 mm (1 1/2 in to 3 1/2 in) thick and 150 mm to 200 mm (6 in to 8 in) wide laid on the flat tongued-and-grooved or splinted edges, and spiked together.

Plastic: A material that contains as an essential ingredient one or more organic substances of large molecular weight.

Plastic cement: Although all caulking cements could be called plastic cements, there is a commonly held acceptance in the roofing industry that plastic cement means bituminous cement, either asphalt or coal tar based. It is a mixture of bitumen, asbestos fibres, filler and suitable solvent. See also flashing cement.

Plastic pan: See pitch pocket.

Plasticizer: A plasticizer is a material, frequently “solvent-like”, incorporated in plastic or rubber to increase its ease of workability, flexibility or extensibility. May be monomeric liquids (phthalate esters), low molecular weight liquid polymers (polyesters) or rubbery high polymers (EVA). Adding the plasticizer may lower the melt viscosity, the temperature of the second order transition, or the elastic modulus of the polymer. The most important use of plasticizers is with PVC where the choice of plasticizer will dictate under what conditions the membrane may be used.

Ply: A single layer or thickness of roofing material in a roofing membrane. A four-ply membrane has at least four plies of felt at any vertical cross section cut through the membrane.

Polyisobutylene (PIB): The polymerization product of isobutylene. It varies in consistency from a viscous liquid to a rubber-like solid with corresponding variation in molecular weight from 1,000 to 400,000.

Polyisocyanurate foam: This insulation material is produced from polyisocyanurate based chemicals. The foam board is sandwiched between asphalt saturated organic or inorganic felt facer sheets.

Polymer: A macromolecular material formed by the chemical combination of monomers having either the same or different chemical composition. Plastics, rubbers, and textile fibres are all high molecular weight polymers.

Polypropylene: A tough, lightweight rigid plastic made by the polymerization of high- purity propylene gas.

Polyurethane (PU): Insulation composed principally of the catalysed reaction product of polyisocyanurate and polyhydroxy compounds, processes usually with fluorocarbon gas to form a rigid foam having a predominantly closed-cell structure. It is sprayed-in-place or preformed into boards. See also insulation.

Polyvinyl Chloride (PVC): A synthetic thermoplastic polymer prepared from vinyl chloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, filler, and other modifiers. The rigid forms are used in pipes, the flexible forms in the manufacture of sheeting for roofing.

Pond: A surface which is incompletely drained.

Ponding: The collection of water in shallow pools on the surface of roofing.

Portland cement: Hydraulic cement used for making concrete and grout.

Positive drainage: 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 following rainfall during conditions conducive to drying.

Pour: A layer of bitumen deposited on the roof surface or the felts by pouring from a bitumen container. See pour coat.

Pourable sealer: 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.

Pour coat: The top layer of bitumen for an aggregate-surfaced built-up roofing membrane, poured or flooded onto the finished felts and over which the aggregate is spread. Also called a pour or a flood coat.

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

Primer: A thin liquid bitumen applied to a surface to improve the adhesion of heavier applications of bitumen and to absorb dust. The most commonly used is asphalt primer.

Promenade: See roof terrace.

Proportional limit: The greatest stress that a material is capable of sustaining without any deviation from proportionality of stress to strain (Hooke’s law). It is expressed in force per unit area.

Protected Membrane Roof (PMR): A roofing system wherein the roofing membrane is applied to a suitable substrate and the insulation is placed on top of the membrane and is ballasted. Also called inverted roof.

Protection mat: A sacrificial material used to shield one roof system component from another.

Purlin: A horizontal structural member spanning between beams, frames or trusses to support a roof deck or the rafters or joists supporting a roof deck.


Rafter: One of a number of closely spaced structural members of a sloped roof, usually extending from the eaves to a ridge or hip on a small roof or between purlins on larger roofs to carry the roof deck.

Rainwater leader: See conductor

Rake: The sloped edge of a roof at the first or last rafter, i.e. at its intersection with a gable.

Re-covering: The process of covering an existing roofing system with a new roofing system.

Reinforced membrane: A roofing or waterproofing membrane reinforced with felt, mat, fabric or chopped fibres.

Reinforcement: A strong inert material bound into asphaltic or polymeric materials to improve its strength, stiffness, and impact resistance. Reinforcements are usually long fibres of glass, sisal, cotton or polymers, in woven or non-woven form. To be effective, the reinforcing material must form a strong adhesive bond with the resin.

Relative humidity: The ratio of water vapour in the air to the water vapour in saturated air at the same temperature and barometric pressure. Approximately, it equals the ratio of the partial pressure or density of the water vapour in the air to the saturation pressure or density, respectively, at the same temperature.

Re-roofing: Replacement of all or part of a roofing system.

Ridge: The horizontal line where two opposite sloping sides of a roof join at the highest level of the roof.

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: The covering of wood, metal or other roofing material that tops the ridge of a roof.

Ridge course: The last or top course of roll roofing, shingles or tiles on a sloping roof cut to length as required.

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: A roofing defect characterized by narrow or relatively narrow ripples in a membrane generally along the machine direction for roofing felts and over deck or insulation joints and usually less than 25 mm (1 in) in height.

Roll goods: A general term applied to rubber and plastic sheeting whether fabric reinforced or unreinforced. They are usually furnished in rolls.

Roll roofing: Any roofing material that is supplied from the manufacturers in rolls, but more specifically applied to coated felts either smooth or mineral-surfaced used for roofing without additional top coatings or surfacing.

Roof: A construction on top of a building that together with walls forms a separator between inside and outside environments. A roof system is a structurally supported, air, heat, interior moisture and rain control combination.

Roof assembly: An assembly of interacting roof components (including structural roof deck) for weatherproofing and thermal insulation.

Roof area divider: A building detail used to limit the size of a continuous roof membrane, dividing a roof into a number of smaller areas. The divider extends only to the roof deck and is not an expansion joint.

Roof cement: See flashing 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.

Roofer’s Pitch: See pitch.

Roof hatch: See scuttle.

Roofing: 1. The material used for constructing a water shedding or waterproofing system. 2. That part of the architectural specifications and building construction contract that deals with the supply and application of roofing materials and systems.

Roofing system: An assembly of interacting components designed to weatherproof, and normally to insulate, a building’s top surface.

Roof insulation: Any medium of low-density material suitable and used as part of a roofing system to reduce heat loss or gain through the roof. See also insulation, board insulation.

Roof system: A system in interacting roof components (not including structural roof deck) for weatherproofing and thermal insulation.

Roof terrace: A traffic-bearing or landscaped roof. Also called promenade, podium or plaza-deck roofs or roof gardens.

Rubber: A polymeric material that, at room temperature, is capable of recovering substantially in shape and size after removal of a deforming force. Refers to both synthetic and natural rubber. Also called an elastomer.

Run: The horizontal distance to which the fall or vertical distance for an inclined roof is referenced. A unit horizontal distance of one metre is taken for the run to which the fall in millimetres is given to describe the incline.


Saddle: A ridge in a roof deck that divides two sloping parts of the surface so that water will be diverted to the roof drains. Usually constructed in a level valley, or behind a projection above a sloping roof. See cricket.

Safety belt: A belt worn around the waist of a worker and all the fittings for the belt appropriate for the use being made of it.

Safety factor: The ratio of the failure load to the specified load or rated load.

Safety net: A safety net that is located and supported in such a way that it arrests the fall of a worker who may fall into it without endangering the worker.

Saturated felt: A felt that has been immersed in hot bitumen; the felt absorbs as much bitumen as it can retain under the processing conditions but remains porous and contains voids.

SBS: See styrene butadiene stryrene.

Screen: An apparatus with circular apertures or mesh for separating sizes of granular material, e.g. aggregates.

Scrim: A woven or non-woven, open mesh reinforcing fabric made from continuous filament yarn. Used in reinforcing the roofing sheeting.

Scupper: An outlet in the wall of a building or a parapet wall for drainage of overflow water from a floor or roof directly to the outside. Special scupper drains connected to internal drains are sometimes installed at roof and wall junctions.

Scuttle: A hatch that provides access to the roof from the interior of the building. The scuttle may have its own curb, or may be placed on a built-up curb. Also called a roof hatch.

Sealant: A mixture of polymers, fillers, and pigments used to fill and seal joints where moderate movement is expected; unlike caulking, it cures to a resilient solid. See also caulking.

Seam: A joint formed by mating two separate sections of material. Seams can be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape, sealant, etc.

Self-adhesive membrane: A membrane that can adhere to a substrate and to itself at overlaps without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane from bonding to itself during shipping and handling.

Self-sealing shingle: An asphalt shingle containing a factory-applied strip or spots of heat sensitive adhesive intended to adhere the overlying shingle once installed on the roof and warmed by the sun.

Selvage: The portion of mineral-surfaced roofing where the mineral surfacing is omitted to allow the overlapping sheet to achieve better adhesion. For double-coverage application the selvage width is half the width of the roll plus about 25 mm (1 in) and for single- coverage, the roll width minus 50 mm (2 in).

Separator sheet: See slip sheet.

Sheathing: board or sheet-type materials fixed to stubbing or roof rafters of joists as the base for application of wall cladding or roof covering.

Sheathing paper: A medium to heavy breather-type building paper or felt, usually asphalt treated, secured to wall or roof deck before the application of the covering material. Most commonly used under shingles in residential construction. Also referred to as underlayment.

Shed: A roof having only one incline that slopes from a higher to a lower wall. A lean-to roof sometimes also called a shed roof.

Shedding: The loss of mineral surfacing from shingles and other prepared roofing.

Sheet: An unrolled piece of roofing felt or other single-ply prefabricated material.

Shingle: 1. A small unit of prepared roofing designed for installation with similar units in overlapping rows on inclines. 2. To cover with shingles. 3. To apply any sheet material in overlapping rows like shingles.

Shingling: 1. The application of any roofing material by overlapping the units in horizontal courses with the overlapping down the slope to shed water. 2. The usual method of laying roofing felts in built-up roofing with overlapping sufficient to produce the number of plies desired.

SI: An abbreviation for the International System of Units.

Side lap: See edge lap.

Single ply membranes: Roofing membranes that are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers.

Single ply roofing: A roofing system in which the principal roof covering is a single layer flexible membrane often thermoset or thermoplastic membrane.

Slag: A gray porous aggregate produced by air cooling and crushing residue from blast furnaces, used as a protective surfacing for shingles, roll roofing and built-up roofing. Also called blast-furnace slag. See also granules.

Slippage: A sliding movement between: (a) adjacent plies or layers of roof membrane in the plane of the bitumen film separating them, (b) the gravel or granule surfacing and the underlying felt, (c) felts in the bitumen pour coat or coating, (d) the membrane and insulation or insulation and deck. Occurs mainly in roofing membranes on a slope, sometimes exposing the lower plies or even the base sheet to the weather.

Slip sheet: Sheet material placed between two layers of a roofing system to assure that there is no adhesion between them. It also protects the lower layer. Also called separator sheet.

Slope: The incline of a roof surface in degrees, as a slope ratio of fall to run, or as a percentage of fall to run. See incline.

Soffit: The underside of any subordinate member of a building. For roofs, the underside of a roof overhang.

Solubility: The amount of a substance that can be dissolved in a given solvent under specified conditions.

Splice: Bonding or joining of overlapping materials.

Split: A membrane tear resulting from tensile stress.

Splitting: The formation of long cracks usually completely through a built-up roofing membrane representing a tension failure of the membrane.

Spot mopping: Application of bitumen in roughly circular spots (400 mm to 500 mm in diameter) in a uniform pattern providing unmopped strips in a grid pattern or between staggered spots.

Spray pond: Intentional ponded water on a roof with a system of piping and jets to spray water above the roof to achieve good evaporation cooling.

Spudder: See scraper.

Square: A roof area of 9.39 m2 (100 ft2), or roofing material required to cover 9.39 m2 (100ft2 ) of deck.

Stabilizer: 1. Water insoluble mineral matter passing a 212um (NO.70) sieve used in a mixture with solid or semi-solid bituminous materials. 2. Various heat and light stabilizers are included in the formulation of PVC for roofing. See also filler.

Stack: A vertical vent pipe penetrating above a roof such as that used to provide an escape for foul gases from plumbing fixtures.

Starter course: The first layer of roofing, applied along a line adjacent to the downslope perimeter of the roof area. With steep-slope watershedding roof coverings, the starter course is covered by the first course.

Starter strip: A strip of felt applied at the eaves or other starting line of built-up roofing to serve as the base for the first full course of roofing.

Steep asphalt: Asphalt of high melting point suitable for steeply-sloped roofs with inclines greater than 1.8. Type 3 Asphalt for BUR as defined by CSA.

Steep roof: A category of roofs that generally include water shedding types of roof coverings weather proof membrane types installed on slopes greater 1 in 4 or 25%

Step flashing: Individual pieces of flashing material used to counter flash chimneys, dormers and other projections along steep-sloping roofs. The individual pieces are overlapped and stepped up the vertical surface. Also called soakers.

Strainer: A wire, plastic or cast-metal cage placed over the top of a roof drain to prevent debris and leaves on the roof from entering the drain.

Strawberry: See blister.

Stress: The force acting across a unit area in solid material in resisting the separation, compressing or sliding that tends to be induced by external forces. Also, the ratio of applied load to the initial cross-sectional area, or the maximum stress in the outer fibres due to an applied flexural load.

Stress concentration: A condition in which a stress distribution has high localized stresses; usually induced by an abrupt change in the shape of a membrane.

Stripping: Narrow widths of felt used to complete flashing details, particularly to cover the edges of metal flanges incorporated into built-up roofing. The technique of completing flashing details with narrow strips of felt or fabric and hot or cold-applied bitumen.

Stripping felt: Narrow widths of felt used to complete flashing details, particularly to cover the edges of metal flanges incorporated into built-up roofing.

Strip shingles: Asphalt shingles that are manufactured in strips, approximately three times as long as they are wide.

Styrene Butadiene Styrene (SBS): High molecular weight polymers that have both thermoset and thermoplastic properties, formed by the block copolymerization of styrene and butadiene monomers. These polymers are used as the modifying compound in SBS polymer modified asphalt roofing membranes to impart rubber-like qualities to the asphalt.

Substrate: The surface upon which the roofing or waterproofing membrane is placed. It may be structural deck or insulation or any other base material.

Sump: A depression around a drain in the roof deck or insulation to provide a water reservoir.

Surfacing: Any aggregate or granular material or coating used as a protective covering on the weather surface of roofing. The protective and traffic-bearing layer of a roof terrace is also called the top cover.

System: An assembly of interacting components. A roof system is designed to weatherproof and normally also to insult the top of a building.


Tab: The exposed portion of strip shingles defined by cutouts.

Tanker: A tank truck specially designed with heating and pumping equipment for conveying and dispensing liquid bitumen.

Tar: Black or dark brown liquid or semi-liquid condensates derived from the heating or baking, sometimes called destructive distillation, of wood, peat, oil shale, bone, petroleum, coal or other organic materials. The word is incorrectly used to describe asphalt as in the expression “tar-and-gravel roofing.”

Tar felt: Felt for which the saturant is coal tar pitch, more properly called coal tar pitch felt.

Tear off: To remove an existing roofing system down to the structural deck.

Thermal: Relating to heat.

Thermal bridge: A heat-conductive element in a roof or wall that extends from the warm to the cold side and provides less heat-flow resistance than the adjacent construction. Maybe of considerable consequence when it passes through the insulation of a well- insulated wall or roof.

Thermal expansion: The increase in the dimension or volume of a body due to temperature variations.

Thermal insulation: See insulation.

Thermal resistance: A measure of the resistance to heat flow of a material or component of construction of a particular thickness. It is the inverse of thermal conductance. The symbol RSI is used. RSI=1/C=(m2°C)/W.

Thermoplastic: Capable of being repeatedly softened by temperature increases and hardened by temperature decreases.

Thermoplastic elastomers: Polymers capable of re-melt, but exhibiting elastomeric properties; related to elasticized polyolefins. They have a limited upper temperature service range.

Thermoplastic Olefin Membrane (TPO): A blend of polypropylene and ethylene-propylene polymers. Colorant, flame retardants, UV absorbers and other proprietary substances which may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.

Thermoset: Unaffected by heat. It is often called elastomer or synthetic rubber. The inertness imparts elasticity and weather resistance.

Through-the-wall flashing: Flashing extending completely through a masonry wall to prevent water from migrating vertically into a wall.

Thru wall flashing: See through-the-wall flashing.

Top cover: See surfacing.

Top pour: The application by pouring of the top layer of bitumen on a built-up roofing. Often used to describe the top layer of bitumen no matter how applied. See also pour coat.

Torch applied: Method used in the installation of polymer modified bitumen membranes characterized by using open flame propane torch equipment.

Travel restraint system: An assembly of components capable of restricting a worker’s movement on a work surface and preventing the worker from reaching a location from which they could fall.

Truss: A combination of members such as beams, bars and ties, usually arranged in triangular units, to form a rigid framework for supporting loads over relatively long spans as in wide span roof construction.


Ultraviolet (UV): Invisible light radiation, adjacent to the violent end of the visible spectrum, with wavelengths from about 200 to 400 nanometres.

Underlay: A material, usually felt, used in covering a roof deck before the roofing materials are applied.

Underlayment: See sheathing paper.


Valley: The horizontal line formed along the depressed angle at the bottom of two inclined roof surfaces.

Vapour: A substance in gaseous state. In relation to building, it generally refers to water vapour.

Vapour retarder: Material used to retard the passage of vapour or moisture into the roof system where harmful condensation of vapour within the system could take place.

Vegetated roof: A roof membrane system with a top layer of living plants in an engineered soil blend (growth medium). Green roof systems are also referred to as vegetated roof covers, roof gardens, eco-roofs, or landscaped roofs.

Vent: An opening designed to convey water vapour or other gas from inside a building or a building component to the atmosphere, thereby relieving vapour pressure.

Vermiculite: An aggregate used for lightweight insulating concrete and roof fills, formed by the expansion of mica rock through heating.

Vertical application: Roof membranes applied with the laps at right-angles to the eaves and parallel to the rake. Also called up-and-over when it continues over the ridge. Sometimes laid slightly on the bias, i.e., by tilting a few degrees to encourage drainage over rather than against the lap.

Viscosity: The internal resistance offered by a fluid to change shape or to relative motion or flow of its parts. The flow characteristics of bitumen is measured in centistokes. Asphalt may vary from 30 to 500 centistokes when heated from 175°C to 260°C (347°F to 500°F) depending on the asphalt type.

Vulcanization: An irreversible process during which a rubber compound, through a change in its chemical structure, e.g. cross linking, becomes less plastic and more resistant to swelling by organic liquids, and elastic properties are conferred, improved, or extended over a greater range of temperature. See also cross linking.


Waterproof: The quality of a membrane, membrane material or other component to prevent water entry.

Waterproofing: 1. A material used to treat or cover a building element or component to prevent leakage of water. 2. Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

Water shedding: The ability of individual, overlapping components to resist the passage of water without hydrostatic pressure.

Weatherproof: The ability of a membrane or roof covering to prevent the passage of water with a limited amount of hydrostatic pressure.

Wet laid non-woven: Fibres are dispersed in water and sheet is formed on an inclined wire. Water is removed by gravity and the web passes over the heating zone to remove excess water.

Wide-selvage roofing: Mineral-surfaced roofing designed for double coverage in which the selvage is slightly greater than half the width of the felt. Also called nineteen-inch selvage (NIS).

Winch: A hoist used for hauling or hoisting materials to the top of a roof.

Wind uplift: The force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface.

Work belt: A belt that has a back support pad and a connecting hook at the front and that is capable of supporting a worker.

Wrinkling: Small ripples formed at the surface of roofing membranes similar to ridging.