October 10, 2012 News No Comments


Algae: Rooftop fungus that can leave dark stains on roofing.

Angled Fasteners: Roofing nails and staples driven into decks at angles not parallel to the deck

APA: American Plywood Association. Tests and sets standards for all varieties of plywoods used in the U.S.

Apron Flashing: Metal flashing used at chimney fronts.

ARMA: Asphalt Roofing Manufacturers Asscociation. Organization of roofing manufacturers

Aspahlt Concrete Primer: Aspahalt based primer used to prepare concrete and metal for asphalt sealant.

Asphalt Plastic Cement: Asphalt based sealant material, meeting ASTM D4586 Type I or II. Used to seal and adhere roofing materials. Also called mastic, blacjack, roof tar and bull.

ASTM: the American Society for Testing Materials. an Organization that sets standards for a wide variety of materials, including roofing.

AIA: American Institute of Architects

Air Blown Asphalt: Asphalt produced by blowing air through molten asphalt held at an elevated temperature. This procedure is used to modify properties of the asphalt.

Alligatoring: The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks that resemble an alligator’s hide.

Aluminized Steel: Sheet steel with a thin aluminum coating on the surface to enhance the steel’s ability to withstand weathering.

Aluminum: A non-rusting metal used in roofing for metal roofing and the fabrication of gutter and flashings.

Apron Flashing: A flashing located at the low end of a curb or penetration.

Architectural Panel: A metal roof panel that usually requires solid decking underneath.

Architectural Shingle: Shingle that provides a dimensional appearance. See also Dimensional Shingle.

Area Divider: A flashed assembly usually extending above the surface of the roof that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas.

ARMA: Asphalt Roofing Manufacturers Association

ASA: American Subcontractors Association

Asbestos: An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.

ASC: Associated Specialty Contractors

ASHI: American Society of Home Inspectors

ASHRAE: American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc.

Asphalt: A substance left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt can be refined to conform to various roofing grade specifications:

    • Dead-Level Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type I. This asphalt is for use in roofs which do not exceed a ¼ in 12 slope (2%).


    • Flat Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II. This asphalt is for use in roofs which do not exceed a ½ in 12 slope (4%).
    • Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. This asphalt is for use in roofs which do not exceed a 3 in 12 slope (25%).
    • Special Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV. This asphalt is for use in roofs which do not exceed a 6 in 12 slope (50%).


Asphalt Emulsion: A mixture of asphalt particles and an emulsifying agent such as bentonite clay and water.

Asphalt Felt: An asphalt-saturated and/or an asphalt-coated felt membrane. (See also Felt.)

Ambient Temperature: The temperature of the air.

Anodic: When two metals are connected in an electrolyte, they will form a galvanic cell, with the higher metal in the galvanic series being the anode. The anodic will oxidize and produce an electrical current which protects the cathode from corrosion.


Back-Surfacing: Granular material added to shingle’s back to assist in keeping separate during delivery and storage.

Blistering: Bubbles or blisters in roofing material. Usually a result of trapped moisture under the material, or moisture trapped inside material itself.

Blow-Offs: Not to be confused with a Roof Blow-Off which is a maintenance term, this term is when shingles are subjected to high winds and are forcewd off the roof deck.

Buckling: When a wrinkle or riplle affects shingles or their underlayments, this could be from plywood not spaced properly, moisture retention in plywood or paper or just shifting from house causing roof deeck to shift as well resulting in buckles.


Closed Cut Valley: A shingle valley installation method where one roof plane’s shingles completely cover the other roof plane. The top layer is cut to match the valley lines.

Corrosion: When rust, rot or age negatively affect roofing metals and metal accessories.

Counter Flashing: The metal or siding material that is installed over roof top base flashing systems.

Crickets: A peaked water diverter installed behind chimneys and other large roof projections. Effectively diverts water around projections so no ponding water occurs which are sources for leaking.

Cupping: when shingles are improperly installed over an existing roof or are over exposed, they form a cup or curl.

Cant Dam: The 45° vertical distance above a roof deck/membrane to the top of a fascia detail, restricting the flow of water over the edge of a roof.

Caulk Cup: A sealant ledge usually located at the top of a termination bar of counter flashing used to receive a bead of waterproofing caulk.

Cleat: A formed metal strip designed to hook into and securely engage the lower most edge of a gravel stop or similar detail; a continuous cleat engages a product along its entire length, fastened 12″ o.c.

Condensation: Water vapor in warm air that changes to liquid when it comes into contact with a colder surface.

Cover Plates: Formed metal pieces ranging from 3½” to 8″ wide which are installed over the joints of abutting gravel stops, copings, gutter and counterflashings to prevent water entry and maintain joint integrity.

Coverage: Refers to the number of nailers or surface dimension to be covered by a certain type of roofing product.


Deck: The substrate over which roofing is applied. Usually plywood, wood boards (also called shiplac, skip sheating) or planks

Dimensional Shingle: A shingle that is textured, or laminated to produce a three-dimensional effect. Also known as Laminated and Architectural Shingles. Please be aware that there are also shingles being produced that can be classified as Dimensional but not as Laminated. These shingles are comprised of a single piece of material rather than two different materials laminated together.

Dimensional Stability: The ability of a material to retain its current properties and to resist a change in size resulting from exposure to temperature changes and moisture.


Dormer: A raised roof extending out from a larger roof plane.

Drip Edge: An installed lip that keeps shingles up off the deck at the edges, and extends shingles out over eaves and gutters, and prevents water from backing up under shingles.

Dry-In: (1) The process of installing the underlayment in steep slope roofing; (2) Making a low-slope roof watertight. Does not always mean getting all of the required plies installed.

Dry Rot: the decay of wood or lumber from certain fungi (Poria incrassata and Serpula incrassata), these fungi require an elevated moisture level to thrive so most dry rot is a result of high moisture levels over a period of time.

D-Drip Edge:

Downspout: A formed metal tube used to carry water from a roof level, scupper/collector box or gutter system to the ground. Closed downspout is capable of transporting large volumes of water. Open face downspout is used where ice or debris clogging causes potential maintenance problems.


Eave: A roof edge that extends out past the exterior wall line.

Eaves-Trough: Another name for gutter

ECH: Polyepichlorohydrin. See also Epichlrohydrin

Edge Stripping: Roofing material used to seal perimeter edge metal and the roof itself.

Edge Venting: The installation of vent material along a roof edge (e.g., Starter Vent) as part of a ventilation system. Edge vent material should be used in conjunction with other venting material (e.g., ridge vent) as it not intended for use by itself.

Elastomer: A material which, after being stretched, will return to its original shape.

Elastomeric: Properties of a material that will permit it to return to its original shape after being stretched.

Elastomeric Coating: A coating that can be stretched to twice its dimensions and that will return to original when tension is released.

Elongation: The ability of a material to be stretched or lengthened.

Embedment: In roofing, to uniformly press one material into another, such as aggregate into bitumen, roofing felt into bitumen, or granules into a coating.

Emulsion: Fine particles suspended in a liquid solution. See also Asphalt emulsion.

End Lap: The extension of one component of material past the end of an adjacent piece of material.

Envelope: A continuous seal for preventing bitumen from leaking down into or off a building. Is constructed by extending the base sheet or other non-porous ply of felt beyond the edge of the field plies. It is then turned back onto the top of the system and adhered. See also. Bituminous Stop

EPDM: Ethylene Propylene Diene Monomer.

Epichlorohydrin (ECH): A synthetic rubber material similar to EPDM with a stronger resistance to animal fats and oils than EPDM.

Epoxy: A type of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.

Equipment Screen: A nonstructural wall or screen constructed around rooftop equipment such as HVAC units, curbs, etc. to hide the look of the equipment and make the structure more aesthetically pleasing.

Equiviscous Temperature (EVT): The temperature at which a bitumen attains the proper viscosity for use in built-up roofing. There is usually a twenty-five degree Fahrenheit (25° F) variance permitted above and below the recommended EVT. The EVT is measured in application equipment just prior to application using a standard thermometer or it can be measured just after application using a laser thermometer.

Ethylene Propylene Diene Monomer (EPDM): A thermoplastic rubber with high tear strength that can be cross-linked by both peroxides and sulfur.

EVT: Equiviscous Temperature

Exhaust Vent: A device used to vent air from the roof cavity with vents that are installed on or near the higher portions of the roof such as the ridge.

Expansion Cleat: A cleat designed to handle thermal movement of the metal roof panels.

Expansion Joint: A built-in separation between building sections to allow for free movement between the sections without damaging the buildings structural components.

Exposed-Nail Method: A method of installing roll roofing materials to where all nails/fasteners are visible and exposed to the elements.

Exposure: The portion of the membrane that is not overlapped by the succeeding ply or course. Or, the portion of the roofing material exposed to the weather after being installed.

Extrusion: The process of manufacturing and/or shaping a material by forcing it through a die.

Eyebrow: A small, shed roof protruding from the main roof or located on the side of a building below the level of the main roof.


Factory Mutual Research Corporation (FMRC): As it relates to roofing – a division of Factory Mutual System that tests and classifies roof components and systems for their resistance to fire, traffic, impact, weathering, and wind-uplift. The various organizations of Factory Mutual are owned or directed by Allendale Insurance, Arkwright, and Protection Mutual Insurance.

Factory Seam: A splice/seam made in the roofing material by the manufacturer. It is preferable during installation to cut these splices out of the membrane.

Fading: Losing brightness or brilliance : dim

Fallback: A reduction in the softening point temperature of asphalt that occurs when asphalt is overheated for pro-longed periods of time. See also Softening Point Drift

Fascia: Vertical roof trim located along the perimeter of a building, usually below the roof level. Its use can be either decorative or for waterproofing.

Fasteners: Devices used to secure roof system components.

Feathering Strips: Strips of wood that are placed along the butt ends of wood shingles to form a somewhat smooth surface so that the shingles can be roofed over without removal.

Felt: A roofing sheet made of interwoven fibers. The fibers can be wood or vegetable for Organic Felts, glass fibers for fiberglass felts, polyester, or asbestos.

Felt Machine: A machine that will install bitumen and felt at the same time.

Ferrule: A metal sleeve used as a spacer to keep gutter from being beat up when secured to fascia with spikes.

Fiberglass Insulation: Insulation composed of glass fibers used to insulate walls and roofs. It can be rigid board or blanket insulation.

Field of the Roof: Refers to the central part of a roof away from the perimeter.

Field Seam: A non-factory material seam made by joining overlapping seams together with adhesives, heat welders, or other means.

Filler: An inert ingredient added to roofing materials in order to alter their physical characteristics.

Fillet: A sealant material installed at horizontal and vertical planes to remove 90° angles.

Film: A membrane or sheeting material with a nominal thickness of 10 mils or less.

Film Thickness: The thickness of a membrane or coating that is expressed in mils (thousandths of an inch). See also Wet Film Thickness and Dry Film Thickness.

Fin: A sharp protrusion in a roof deck that can damage roof components.

Fine Mineral-Surfacing: A fine mineral material on the surface of roofing materials to prevent them from sticking to surfaces. 50% of this material has to pass through a sieve with holes that are 1/35″ in size (#35 sieve).

Fishmouth: An opening along the exposed edge of an installed ply of felt caused by shifting the ply during installation. Repair these by making a slice along their entire length and feathering two plies of felt over the fishmouth for a minimum coverage of one foot all the way around.

Flaking: Occurs when a coating loses its cohesion.

Flame Retardant: A substance used to impede a material’s tendency to burn or ignite.

Flame Spread: Per ASTM E 84, a measure of relative combustibility. The flame spread of a tested material is rated relative to asbestos cement board (flame spread = 0) and red oak flooring (flame spread = 100).

Flammability: The ability of a material to burn or ignite.

Flange: A projection edge of a roof component such as flashings, skylight frames, pre-manufactured curbs, etc. Usually refers to the part that sits on the roof surface.

Flash: v. To install flashing components.

Flash Point: The lowest temperature of a liquid material at which combustion will occur when air reaches its surface.

Flashing: Components used to seal the roof system at areas where the roof covering is interrupted or terminated. For example, pipes, curbs, walls, etc. all have special components that, when correctly installed, will help prevent moisture entry into the roof system or building.

Flashing Cement: A trowelable mixture of solvent-based bitumen and mineral stabilizers. Flashing cement that may contain asbestos stabilizers is categorized by ASTM standard D 2822-91 (1997) or for non-asbestos, ASTM standard D 4586-93. Flashing Cement is the term for Asphalt Roof Cement that can be used on vertical surfaces and has a high softening point, low ductility and conforms to the requirement of ASTM Specification D 312, Types II or III; or Specification D 449, Type III. See also Asphalt Roof Cement and Plastic Cement.

Flashing Collar: A flashing component used to seal soil pipe vents, hot stacks or other roof penetrations.

Flat Lock: A type of interlocking two separate metal panels by folding one panel over on top itself and the folding the other down under itself and then hooking the panels together.

Fleece: Mats or felts used as a membrane backer and composed of fibers.

Flood Coat: The surfacing layer of bitumen into which aggregate is embedded on an aggregate-surfaced built-up roof. A flood coat is applied at an approximate rate of 45 to 60 pounds per square (100 square feet).

Flood Test: A water test performed to determine the effectiveness of a roof covering.

Flow: To become fluid in character.

Fluid-Applied Elastomer: A liquid elastomeric material that cures to form a continuous waterproofing membrane.

FM: Short for Factory Mutual Research Corporation.

Foam Stop: The edge metal used to terminate Sprayed Polyurethane Foam.

Framed Opening: an structurally-framed opening in a roof of a building for use in installing large items such as HVAC units, skylights, or ventilators.

Froth Pack: A term used to describe small, disposable aerosol cans of SPF.


G-90: A coating weight for galvanized sheet metal, 0.90 ounces of zinc per sq. ft., measured on both sides of the sheet.

Gable: A triangular-shaped portion of the endwall of a building directly under the sloping roof and above the Eave line. .

Gable Roof: A roof configuration that has gable ends.

Gable-On-Hip Roof: A roof configuration with hips coming up from the eave corners that terminate into a gable roof.

Galvalume: Trade name for a protective coating composed of aluminum zinc.

Galvanic Action A reaction between different metals in the presence of an electrolyte.

Galvanize: To coat with zinc.

Galvanized Steel: Steel that is coated with zinc to aid in corrosion resistance. Galvanized steel for use in roofing should be Hot-Dipped Galvanized with a G-90 coating.

Gambrel: A roof that has two different pitches.

Gauge: A standard of measurement. For instance the thickness of sheet metal or the diameter of wire. The thicker the wire or metal, the lower the gauge.

Geodesic Dome: A geodesic dome uses a pattern of self-bracing triangles in a pattern that gives maximum structural advantage, thus theoretically using the least material possible. (A “geodesic” line on a sphere is the shortest distance between any two points.) The first contemporary geodesic dome on record was designed by Walter Bauersfeld.

Girt: A horizontal beam place between support columns that is used for attaching wall cladding.

Glass Felt: (1)In the manufacturing of roofing materials – a sheet comprised of bonded glass fibers prior to being saturated with bitumen; (2) short for asphalt or coal tar saturated fiberglass felt membrane.

Glaze Coat: (1) The uppermost layer of asphalt on a smooth-surfaced built-up roof membrane, usually a reflective surfacing is installed over it; (2) A thin coat of bitumen applied to help protect the roof membrane when application of additional

felts or the flood coat and aggregate surfacing are delayed.

Grain: A unit of measure for the mass of moisture: a unit of weight equal to 0.002285 ounces or 0.036 dram.

Granule: A small aggregate, naturally or synthetically colored, used to surface cap sheets, shingles, and other granule-surfaced roof coverings.

Gravel: Aggregate consisting of rock fragments or pebbles.

Gravel Stop: A flanged, sheet metal edge flashing with an upward projection installed along the perimeter of a roof to stop the flow of bitumen over the edge.

Grout: A thin mortar used to fill cracks in masonry and tile.

Grout (Non-Shrink): A cementitious material used to partially fill penetration pockets (pitch pans). A pourable sealer is used afterward.

Gutter: A channel (usually sheet metal) installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.


Half Gable Roof: See Shed Roof

Hand-Tabbing: Applying spots of adhesive to shingle tabs.

Hatch: A unit used to provide access to a roof from the interior of a building.

Headlap: The distance that the topmost ply of roofing felt overlaps the

undermost ply or course.

Heat Seaming: See Heat Welding.

Heat Transfer: Thermal energy going from an area of higher temperature to an area of lower temperature by conduction, convection, or radiation.

Heat Welding: Fusing the seams of separate sections of roofing material together through the use of hot air or an open flame and pressure. Also known as heat seaming.

Hem: The edge created by folding metal back on itself. Metal is hemmed for safety and strength reasons.

Hip: The angle formed by the intersection of two sloping roof planes.

Hip Roof: A roof that rises by inclined planes on all sides of a building. The line where two adjacent sloping sides of a roof meet is called the Hip.

Hoist: A mechanical lifting device. A hoist can be hand or electrically operated.

Holiday: An area where a liquid-applied material is missing.

Honeycomb: Small voids left in concrete because the mortar failed to fill the spaces around the aggregate.

Hot: Slang for hot bitumen.

Humidity: The amount of water vapor in the air.

HVAC: Acronym for Heating, Ventilating, and Air Conditioning.

Hypalon: The trademark name for Chlorosulfonated Polyethylene (CSPE), which is a single-ply roofing material.


ICBO: International Conference of Building Officials, responsible for The Uniform Building Code.

Ice Dam: Ice formed at the transition from a warm surface to a cold surface, such as along the overhang of a house. The build-up of ice is the result of ice or snow melting on the roof area over the warmer, living area of a building and then refreezing when it runs down and reaches the overhang.

Ignition Temperature: The minimum temperature at which a material will combust.

Impact Resistance: A roof assembly’s ability to withstand the impact from falling objects such as hail.

Impregnate: To saturate; in roofing, asphalt impregnated fiber glass roofing felts are fiber glass mats that have been completely permeated with asphalt bitumen.

Infrared Thermography: The use of an infrared camera to detect moisture in roof insulation.

Inorganic: Involving neither organic life nor the products of organic life; relating to compounds not containing hydrocarbon groups.

Insect Screen: Material used to inhibit an insects ability to enter a building through openings in a roof such as vents.

Insulation: Material used to help maintain a certain temperature in a building by reducing the flow of heat to and from that building. See also Thermal Insulation.

Intake Ventilation: The part of a ventilation system used to draw fresh air in. Usually vents installed in the soffit or along the eaves of a building.

Interlayment: A waterproof material usually installed between adjacent rows of wood shakes to help with the roof’s waterproofing characteristics.

Interlocking Shingles: Shingles that lock together to provide wind resistance. See also T-Lock.

Internal Pressure: Atmospheric pressure inside a structure that correlates to the number and location of openings and air leaks.

Inverted Roof Membrane Assembly (IRMA®): A variation of the “Protected Membrane Roof Assembly” in which Styrofoam® brand insulation is used. IRMA® and Styrofoam® are registered trademarks of the Dow Chemical Company.

IRWC: Institute of Roofing and Waterproofing Consultants

ISANTA: International Staple, Nail & Tool Association

Isocyanate: A highly reactive organic chemical containing one or more Isocyanate groups. A basic component in Sprayed Polyurethane Foam systems and some polyurethane coating systems.


Jack: See Roof Jack

Joint Tape: Tape used to seal joints between insulation boards.

Joist: Any of the parallel horizontal beams set from wall to wall to support the boards of a floor, ceiling or roof of a building.


Knee Cap: Sheet metal trim that fits over a panel rib after it has been cut and bent.



Laitance: An accumulation of fine, powdery aggregate particles on fresh cement caused by the upward movement of water; indicates that too much water was used in the mix resulting in poor surface adhesion for a waterproofing layer.

Laminated Shingles: See Dimensional Shingles or Architectural Shingles.

Lap: The part of the roofing material that overlaps a section of adjacent material.

Lap Cement: Asphalt-based roof cement used to adhere overlapping plies of asphalt roll roofing.

Lap Seam: Where two material that overlap are sealed together.

Lead: Metal used for flashing material.

Leader Head: A component used to direct water from a through-wall scupper to a downspout. Also known as a Collector Head.

Leader Pipe: A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level. Also known as Downspout.

Lift: The rise in Sprayed Polyurethane Foam resulting from a pass.

Live Loads: Temporary items on a roof such as equipment, people, snow, etc. which the roof must be designed to support.

Loose-Laid Roof Membranes: Roofing material attached only at the perimeter and at penetrations and held in place by ballast, pavers, or other materials.


Material Safety Data Sheets (MSDS): Written descriptions of the chemicals in a product provided by the product’s manufacturer. MSDS also contain other information such as emergency procedures and safe handling.

MBMA: Metal Building Manufacturers Association

MCA: Metal Construction Association

Mechanical Damage: Damage to a roof by means of items puncturing or otherwise unnecessarily penetrating the roof system or any of its components. Screws or nails stuck in the roof and heel marks along base flashings are examples of mechanical damage.

Mechanical Fasteners: Devices such as screws, plates, battens, nails, or other materials that are used to secure roofing materials.

Membrane: The portion of the roofing system that serves as the waterproofing material. Can be composed of one material or several materials laminated together.

Metal Flashing: Roof components made from sheet metal that are used to terminate the roofing membrane or material along roof edges. Metal flashings are also used in the field of the roof around penetrations.

Meter: Metric unit of length measurement equal to 39.37 inches.

Mil: A unit of measure equal to 0.001 inches (1/1000 in.) used to indicate the thickness of a roofing membrane.

Mildew: A superficial coating or discoloration of organic materials caused by fungi, especially under damp conditions.

Millimeter: Metric unit of measure equal to one thousandth (0.001) of a meter, or 0.03937 inches.

MIMA: Mineral Insulation Manufacturers Association

Mineral Fiber: Inorganic fibers of glass or rock.

Mineral Granules: See Granules.

Mineral-Surfaced Roofing: Roofing materials with a top surface consisting of mineral granules.

Miter: The joint made by two diagonally cut pieces put together.

Model Codes: A group of codes and standards accepted by more than one of the Building Code regulatory agencies such as SBCCI, BOCA, and ICBO

Modified Bitumen: a bitumen modified by one or more polymers such as Atactic Polypropylene (APP), styrene butadiene styrene (SBS).

Moisture Relief Vent: A vent installed through the roofing membrane to relieve moisture vapor pressure that has been trapped within the roofing system.

Moisture Scan: A survey of a roof specifically to detect the amount of moisture present in the roof system. Devices used in moisture surveys can be capacitance meters, infrared cameras, and nuclear scanners. Infrared scans can be done from the air or on the surface of the roof. Capacitance and nuclear scans are done on the roof surface. It is argued that the most accurate scans are done from the surface of the roof with the most accurate of these being nuclear scans.

Mole Run: A term used to describe a ridge in a roof membrane that is not the result of improper deck or insulation joints.

Monolithic: Used to describe something without seams; formed from a single material.

Monomer: A simple molecule that can combine with other to form a polymer.

Mop-and-Flop: A roofers’ term where the back side of a roofing material is mopped, then the piece is turned over and set in place.

Mopping: To apply hot asphalt or coat tar using a hand mop or mechanical applicator.

Mud Cracking: Surface cracking of a material that looks similar to dried, cracked mud.

Multiple Coats: More than one layer of coating applied to a substrate.


NAHB: National Association of Home Builders

Nailer: A piece of lumber, preferably treated, that is secured to the deck, walls, or to premanufactured curbs. Nailers are used to receive fasteners for roof membranes. Generally, nailers are installed wherever it is necessary to secure base flashings and edge metal.

Nailing Pattern: Refers to a specific method or pattern at which nails are applied. For instance, a nailing pattern for base sheets on plywood roof decks can be “Nine and Eighteen”. This means one row of nails on the outside edge of the sheet set at nine inches (9″) on center, and two rows in the center of the sheet, each set at eighteen inches (18″) on center.

Neoprene: A synthetic rubber produced by polymerization of Chloroprene for use in liquid-applied and sheet-applied elastomeric roofing.

Nesting: To overlay existing shingles with new shingles and butt the top edge of the new shingle up against the bottom edge of the existing shingles.

Net Free Vent Area: The area permitting unrestricted air flow.

Newton (N): In the meter-kilogram-second system, the unit of force required to accelerate a mass of one kilogram one meter per second per second (s².)

NICA: National Insulation Contractors Association

Night Seal: To temporarily seal the edge of a roof membrane in order to protect it from moisture entry. A.K.A. Night Tie-Off and Water Cut-Off.

Ninety-Pound: Granule-surfaced or fiber glass or organic felt roll roofing that has a mass of approximately 90 pounds per 100 square feet.

NIST: National Institute of Standards and Technology

Noble: In reference to metal, inert or inactive.

No-Cutout Shingle: A shingle made of one solid strip of material.

Non-Breathing Membrane: A membrane that does not permit water vapor or air to permeate it.

Non-Flammable: Material with no measurable flash point.

Non-Friable: Refers to a material’s inability to be crushed or pulverized into a powder.

Non-Volatile Content: The portion of a material that will not evaporate.

Non-Vulcanized Material: A material that retains its thermoplastic properties throughout its service life.

Nonwoven: Random arrangement of the reinforcement fibers of a scrim sheet or mat.

Nosing: Metal flashing bent at a 90º angle and is installed around roof perimeters, curbs, platforms, etc. in order to protect the edge of the roofing system. Nosing should not be used in place of drip edge. To see the difference in the two.

NRCA: National Roofing Contractors Association.

NTRMA: National Tile Roofing Manufacturers Association


Objectivism¹: The philosophy of Ayn Rand. The concept of man as a heroic being, with his own happiness as the moral purpose of his life, with productive achievement as his noblest activity, and reason as his only absolute.

Off-Ratio Foam: SPF where the 1 to 1 ratio of the A and B components has been compromised and which results in a lower quality material.

Open Time: The time after an adhesive has been applied and permitted to cure when the two surfaces can be bonded.

Open Valley: A valley where both sides of the roof are trimmed back from the centerline to expose the valley flashing material beneath.

Orange Peel Surface Texture: A surface with a texture comparable to the skin of an orange upon which a protective coating may be applied.

Organic: Formed from hydrocarbons.

Organic Felt: An asphalt roofing base material manufactured from cellulose fibers.

Organic Shingle: An asphalt shingle reinforced with organic material manufactured from cellulose fibers.

ORNL: Oak Ridge National Laboratory

OSB: Oriented Strand Board – Often used as roof sheathing in place of plywood.

Overlay: See Re-Cover.


Pallet: A platform, generally from wood, used to hold materials.

Pan: (1) The concave piece of “Pan and Cover” tile whose rounded surface touches the top side of the roof substrate. (2) The flat part of a roofing panel located between the ribs.

Pan Flashing: A sheet metal flashing that covers an equipment platform and is designed to counter flash the base flashings surrounding the platform.

Parapet Wall: That part of a perimeter wall that extends above the surface of the roof.

Pass: The term used to describe the application of one layer of Spray Polyurethane Foam (SPF). The speed of a pass will determine foam thickness.

Pass Line: The distinct line formed between two passes of SPF. This line is the top skin of the bottom pass of the SPF.

Penetration: Any object that pierces the surface of the roof.

Percent Elongation: The maximum amount that a material can be lengthened or stretched before breaking; expressed as a percentage of the original length of material tested.

Perlite: A natural volcanic glass having distinctive concentric cracks and a relatively high water content.. Perlite in a fluffy heat expanded form is used in lightweight insulating concrete, fire-resistant rigid insulation board (R = 2.78 per inch) and potting soil.

Perm: A unit of water vapor transmission, defined as one grain of water vapor per square foot per hour per inch of mercury (Hg) pressure difference (1 inch of mercury = 0.491 psi).

Permeability: The rate of flow of a liquid or gas through a porous material.

pH: A measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14.

Phasing: Installing roof system components in separate time intervals. For instance, installing a base sheet, and then two plies of roofing one day, and coming back and installing the remaining two plies one or more days later. It is generally not considered Phasing if the surfacing is applied at a later date.

Picture Framing: Rectangular patterns seen in a roof that are created by buckles or ridges in the roof system or sumps in the substrate.

PIMA: Polyisocyanurate Insulation Manufacturers Association

Pinhole: A small hole in a coating, foil, membrane, or other roofing material.

Pipe Boot: A prefabricated flashing piece used to flash around circular pipe penetrations. Also known as a Roof Jack.

Pitch: Term used to describe Roof Slope and also short for Coal Tar Pitch.

Pitch Pocket (A.K.A. Pitch Pan): A flanged piece of flashing material placed around irregularly shaped roof penetrations and filled with grout and a pourable sealer to seal around the penetration in order to seal it from against moisture entry. Pitch pockets are a good source of leaks and should be avoided if possible. For an example on how to properly fill a pitch pocket.

Pittsburgh Lock Seam: A method of interlocking two separate pieces of metal.

Plastic Cement: A term used to describe Type I asphalt roof cement. Plastic cement should not be used on vertical surfaces. See also Asphalt Roof Cement and Flashing Cement

Plastic Film: A flexible sheet made by the extrusion of thermoplastic resins.

Plasticizers: Material incorporated into rubber and plastic in order to increase their flexibility and workability.

Plenum: A space or enclosure in which air or other gas is at a pressure greater than that of the outside atmosphere.

Ply: A layer of felt or other reinforcement material in a roof system.

Polyester: Any of numerous synthetic polymers produced chiefly by reaction of dibasic acids with Dihydric alcohols and used primarily as light, strong, weather-resistant resins. In roofing, polyester is used to reinforce fabrics.

Polymer: Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule.

Polymer Modified Bitumen: See Modified Bitumen.

Polymeric Methylene Diphenyl Diisocyanate (PMDI): The “A” component in SPF; when mixed with “B”, it forms polyurethane. PMDI is an organic chemical compound having two reactive Isocyanate (-N=C=O) groups.

Polymerization: The combining of monomers to produce polymers.

Polypropylene: Any of various thermoplastic resins that are polymers of propylene. They are hard and tough, and are used to make molded articles and fibers.

Polyvinyl Chloride (PVC): A thermoplastic polymer that 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.

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

Pop Rivet: A small metal pin having a head on one end, inserted through aligned holes in pieces of light gauge metal to be joined and then the head is expanded to join the metal.

Popcorn Surface Texture: A coarse surface texture of SPF considered unacceptable for coatings.

Positive Drainage: The drainage condition of a roof where all water is gone from the roof surface within forty-eight hours of precipitation during normal drying conditions.

Pot Life: The period of time during which a material with multiple ingredients can be applied or administered after being mixed together.

Pourable Sealer: A type of sealant that is initially in liquid form commonly used in conjunction with pitch pans to form a water-tight barrier around penetrations that are difficult to flash.

Press Brake: A mechanical device used to form sheet metal into desired shapes and profiles.

Primer: A material that is applied to a surface in order to increase that surface’s ability to adhere to or work in conjunction with a subsequently applied material.

Proportioner: A pumping unit comprised of two (2) positive displacement pumps that is designed to dispense two (2) components at a precise ratio. Used in SPF and plural component coating applications.

Protected Membrane Roof (PMR): A roof assembly in which the insulation and ballast are placed on top of the membrane component. Commonly referred to as an “inverted roof assembly.”

Psychrometer: An instrument that uses the difference in readings between two thermometers, one having a wet bulb and the other having a dry bulb, to measure the moisture content or relative humidity of air.

Puncture Resistance: The ability of a material to withstand being pierced by a sharp object.

Purlin: Horizontal secondary structural member used to transfer loads from the primary structural members.

PVC: Polyvinyl Chloride.


Radian Barrier: a reflective surface that intercepts the flow of radiant energy to or from a building component.

Raggle: A groove that is cut into the side of a vertical surface such as a wall or chimney that is used to insert a flashing element such as a reglet or counterflashing.

Rake: The sloped perimeter edge of a roof that runs from the eaves to the ridge. The rake is usually perpendicular to the eaves and ridge.

Rake-Starter: A starter strip placed along rake edges for use in asphalt shingle roofing. See also Bleeder Strip.

RCI: Roof Consultants Institute

RCMA: Roof Coatings Manufacturers Association

RDCA: Roof Deck Contractors Association

Re-Cover (Overlay): The installation of a new roof system over an existing system without removing an existing system.

Reglet: A receiver, usually sheet metal, that counterflashings are attached to. Reglets can be surface-mounted, set in a raggle, or be part of the wall assembly.

Reinforced Membrane: A roofing membrane that has been strengthened by adding polyester scrims or mats, glass fibers or other material.

Relative Humidity: The amount of water vapor in the air compared to the amount of water vapor that the air can hold at a given temperature. For example, if the relative humidity is 50 percent, then the amount of water vapor in the air is half of what the air could actually hold at that temperature.

Remove and Reinstall: To remove a component and reuse that component by reinstalling it.

Remove and Replace: To remove a component and replace it with a new component of the same or similar type.

Reroofing: The procedure of installing a new roof system.

Resin: The “B” component in SPF that is mixed with the “A” component in order to form polyurethane. Resin contains a catalyst, fire retardants, a blowing agent, Polyol, and a surface active agent.

Ridge: The line where two planes of roof intersect, forming the highest point on the roof that runs the entire length of the roof.

Ridge Cap: Material applied over the ridge or hip of a roof.

Ridge Course: The final course of roofing applied that covers the area where two or more roof planes intersect.

Ridge Vent: An exhaust venting device located at the ridge of a roof that works in conjunction with a starter or under eave soffit vent and is used to ventilate attics. Ridge vents and their cooperative starter or soffit vents should be installed at a 1:1 ratio in order to function properly.

Ridging: The formation of a Buckle.

RIEI: Roofing Industry Educational Institute

RMA: Rubber Manufacturers Association

Roll Goods: The term used for all roofing materials that come in rolls.

Roof Assembly: A term used to describe all of the roof components including structural roof deck.

Roof Cement: See Asphalt Roof Cement and Coal Tar Roof Cement.

Roof Covering: The outermost reinforced layer of the roof assembly. In BUR it’s the multiple-ply membrane, in Thermoplastic roof systems it’s the thermoplastic sheet, etc.

Roof Curb: A frame used to structurally mount rooftop equipment such as HVAC units, exhaust fans, skylight, etc.; may be pre-constructed or constructed on site.

Roofer: An individual who installs roof systems and materials.

Roof Jack: (1) A steel bracket fastened to the roof that is used to support toe boards. (2) A term used to describe a Pipe Boot or Flashing Collar.

Roof Overhang: That portion of the roof that extends beyond the exterior wall line of the building.

Roof Seamer: (1) A mechanical device used to crimp metal roof panels and make the seams watertight. (2) A machine used to weld membrane laps of PVC (Thermoplastic) roofing material.

Roof Slope: The angle made by the roof surface plane with the horizontal plane and expressed as the amount of vertical rise for every twelve inch (12″) horizontal run. For instance, a roof that rises four inches (4″) for every twelve inch (12″) horizontal run, is expressed as having a “four in twelve” slope; often written as “4:12.” Expressed as a percentage, the slope would be 33%, which is equal to 4 divided by 12. Also known as the Pitch of a roof. For more information on Roof Slope.

Roof System: Multiple roof components assembled to provide waterproofing (and sometimes insulating) capabilities for a structure.

Rosin: Non-asphaltic material used as slip sheets and sheathing paper in roof systems. Also referred to Rosin Paper and Rosin-Sized Sheathing Paper.

Run: The horizontal dimension of a slope.

Rust Blush: Early stage of rust indicated by an orange or reddish color.

Overspray: The loss of spray particles (from coatings, SPF, etc.) in the air.


Saddle: (1) A type of flashing usually used in conjunction with step, counter, and apron flashings on steep slope roof systems. (2) A small, somewhat pyramid-shaped figure constructed in between sump drains that is used to direct run-off water toward the sump drains.

Sag: Settling or drooping of base flashings that have not been properly secured to a surface.

Saturated Felt: Felt that has been saturated with bitumen.

SBCCI: Southern Building Code Congress International, Inc.

SBS: Styrene Butadiene Styrene.

Scarfed: Shaped by grinding.

Screeding: Bringing the surface of concrete to the final, desired look and finish by removing any excess or unwanted material.

Scrim: Woven or nonwoven material used to reinforce membranes; it is usually laminated or coated to produce the membrane.

Scuttle: A unit that provides access to the roof from the interior of the building. See also Hatch.

SDI: Steel Deck Institute

Sealant: Generic term for a multitude of materials used to seal joints or junctures against moisture or weather.

Sealer: Coating designed to prevent bleedout or bleed-through.

Seam: A line, ridge, or groove formed from fitting, joining, or lapping two sections together.

Self-Adhering Membrane: A type of membrane whose bottom surface will stick or adhere to a substrate without the use of an additional adhesive material.

Self-Drilling Screw: A screw with a small drill-bit like tip that will drill its own hole and eliminate the need to pre-drill a hole.

Self-Sealing Shingle: Asphalt shingles with adhesive strips that will soften and stick to the following course of shingles when heated by the sun; used to help against wind uplift.

Self-Tapping Screws: Fasteners that make screw thread receivers when screwed into a hole.

Self-Vulcanizing Membrane: Membrane that is initially thermoplastic in nature but that cures after installation.

Selvage Edge: That portion of a granule-surfaced membrane that is designed to be overlapped by the following membrane course; usually two, four, or nineteen inches in width.

Shark Fin: A curled corner or lap in a membrane.

Shed Roof: A roof with only one sloping plane. Also known as Half Gable.

Shelf Life: The length of time between the manufacture of a material and when the material is no longer suitable for use.

Shiner: Term used to describe an exposed nail; one that was not covered by the following course of roofing material.

Shingle: (1) A single piece of prepared roofing material, either asphalt or wood, for use in steep slope roof systems. (2) To install a wood or asphalt shingle roof system.

Shingle Fashion: Refers to the way courses of like materials are overlapped in order to have multiple layer coverage.

Shrinkage: The process of shrinking; depreciation in size.

Shrinkage Crack: A crack caused by material shrinkage. May be the result of thermal expansion/contraction, material failure, or cure.

SI: The international system of weights and measures (metric system). Système International [d’Unit[eacute]s]

Side Lap: The longitudinal overlap of neighboring materials.

Siding: Exterior wall finish materials applied to the outside of a structure.

Sill: The bottom framing member of a door or window opening.

Sill Flashing: Flashing material(s) used to waterproof the bottom framing member of a door or window opening.

Single Coverage: One layer of roofing material.

Single-Lock Standing Seam: A standing seam system with one overlapping interlock between two seam panels.

Single-Ply Membranes: Roofing membranes that are applied in one layer. Thermoplastic and thermoset membranes are usually Single-Ply Membranes. Single-Ply membranes come in five basic types: (1) Ballasted, (2) Fully-Adhered, (3) Mechanically-Fastened, (4) Partially-Adhered, and (5) Self-Adhered. Seams of Single-Ply Membranes can be heat welded, solvent welded, and adhered using seam tape or other adhesives.

Single-Ply Roofing: Roofing systems where the principal component consists of a single-ply membrane.

Skylight: A transparent or translucent item that is designed to admit light and set over a curbed opening in the roof.

Slag: Residue from blast furnaces that is sometimes used for the surfacing on aggregate-surfaced built-up roof systems.

Slate: A fine-grained metamorphic rock that splits into thin, smooth-surfaced layers used in steep slope roofing applications.

Slating Hook: A hook-shaped device used to secure roofing slate.

Slip Sheet: Sheeting material placed between roofing components to prevent those components from adhering to one another or to prevent material damage due to component incompatibility. Slip Sheets may be polyethylene, rosin-sized sheathing paper, or other material.

Slit Sample: A cut made in SPF roofing to measure coating thickness. The cut should be about 1.5″ long by ¾” deep by ½” wide.

Slope: The angle of incline of a roof expressed as a percent or as a ratio of rise to run. See Roof Slope

SMACNA: Sheet Metal and Air Conditioning Contractors National Association

Smooth Surface Texture: In SPF roofing, a relatively smooth surfaced texture that is considered ideal for receiving the base coating.

Smooth Surfaced Roof: A roof with no surfacing or with a smooth surfacing such as emulsion and/or a reflective coating.

Snow Guard: Devices secured to the roof to prevent snow and ice from sliding off of a roof.

Snow Load: A roof load resulting from snowfall. Snow load is a major structural consideration when roofs are designed in areas that receive heavy snow.

Soffit: The underside of a roof overhang.

Soffit Vent: An intake ventilation device located in the soffit. An exhaust vent should be installed on or near the ridge of the roof to work in conjunction with the soffit vent in order to properly ventilate the attic space. The ratio of intake vent area to exhaust vent area should be 1:1.

Softening Point: The temperature at which bitumen will begin to Flow.

Softening Point Drift: A change in the softening point of bitumen. See also Fallback

Soil Pipe: A pipe that penetrates a roof and is used to vent a building’s plumbing.

Solder: Any of various fusible alloys, usually tin and lead, used to join metallic parts.

Solid Mopping: To continuously apply hot asphalt or coal tar leaving no areas without bitumen.

Solvent: (1) A liquid capable of dissolving other substances such as bitumen. (2) A liquid that is part of a substance and is used to make that substance easier to work with. Once applied, the solvent evaporates and leaves the working characteristics of the substance. Examples are solvent-based adhesives and solvent-based mastics.

Solvent Weld: To weld materials using a liquid solvent.

Spall: A chip, fragment, or flake from concrete or masonry.

Special Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV. This asphalt can be used on roofs with slopes up to 6 in 12 (50%).

Specification: Written requirements for a construction project; contains but is not limited to the following: the scope of work, methods of construction, and materials.

SPF: Sprayed Polyurethane Foam.

SPF Compounds: Refers to the Isocyanate and resin components used to make polyurethane foam.

SPI: The Society of the Plastics Industry

SPI/SPFD: The Society of the Plastics Industry/Sprayed Polyurethane Foam Division

Splash Guard: A fabricated metal pan or masonry block that is placed below a leader pipe or downspout and is used to help protect the roof membrane on a lower roof level or to prevent soil erosion when placed on the ground.

Splice: To join by overlapping along ends.

Splice Plate: A metal plate placed beneath the joint between two pieces of metal.

Splice Tape: A self-adhering (usually double-sided) tape used for splicing membrane materials.

Split: The separation of a material resulting from tensile forces.

Sprayed Polyurethane Foam (SPF): A monolithic sprayed-on roofing material with a high R-value; formed when isocyanate (“A” component) and resin (“B” component) are mixed at a 1:1 ratio.

SPRI: Single Ply Roofing Institute

Sprinkle Mopping: To scatter hot bitumen over a surface.

Spud: To remove the top surfacing of a roof by scraping it with special tools called spud bars or power spudders.

Spud Bar: A long-handle tool with a stiff flat blade on one end (usually 4″ or 6″ wide) that is used to scrape and remove the top surfacing of a roof down to the membrane.

Spunbond: Describes nonwoven fabrics made from continuously bonded fibers.

Spunlaced: Describes nonwoven fabrics that have the fibers intertwined by water-jet method.

Square: (1) 100 square feet of roof area (9.29 m2) in the USA. (2) 10 square meters (107.639 ft.2) of roof area using the metric system of weights and measures.

Stack Effect: The occurrence where air escapes through opening in the upper part of a building and is replaced with outside air which enters through an opening lower down. In roofing, the Stack Effect helps create proper air flow for attic or roofspace ventilation. The Stack Effect will be affected by atmospheric conditions such as temperature and wind.

Stainless Steel: A highly corrosion resistant steel alloy containing either chromium, nickel, or copper.

Stair Step: The diagonal method of laying shingles.

Standing Seam: A type of metal roof system where the longitudinal seams on adjacent panels are turned up, overlapped and folded in various ways in order to prevent moisture entry and interlock the panels.

Starter Course: The primary course of roofing materials. The Starter course is installed along the downslope perimeter edge and usually covered by the first course of roofing.

Starter Plies: Felt or ply sheets that are cut into widths that are proportionate to the reciprocal of the number of plies being installed. For instance, with a three-ply built-up roof, the first starter ply would be one-third of the roll width, the second two-thirds of the roll width installed over it, and then a full ply over those.

Starter Strip: Strips of shingles (usually 3-Tab shingles with the tabs cut off) or roll roofing material that is laid along the eave line of the roof prior to the application of the first course of shingles. The starter strip is used to fill in the gaps created by shingle cutouts and joints.

Static Load: Roof loads that do not move such as HVAC units.

Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. This asphalt can be used on roofs with slopes up to 3 in 12 (25%).

Steep-Slope Roof: A roof with a slope exceeding 3 in 12 (25%). Deemed appropriate to receive water-shedding type roofing materials such as asphalt shingles, wood shakes and shingles, concrete or clay tile, etc.

Steep-Slope Roofing Materials: Roofing materials that depend on their water-shedding capabilities to keep moisture from entering a building. These materials are generally installed on roofs with slopes that equal or exceed 3″ in 12″ (25%).

Steeple: A tall tower forming the superstructure of a building, such as a church or temple, and usually surmounted by a spire.

Step Flashing: Pieces of metal or other material that are used to flash roof projections such as chimneys, walls, curbs, etc. The pieces are installed between each course of roofing and generally have a vertical flange equal in length to that of the horizontal flange.

Strapping: Installing roofing felts so that they run parallel with the slope. Not a recommended installation method for slopes that are 1:12 or less.

Strawberry: See Tar Boil

Straw Nail: Long-shanked nails used to fasten tile along hips and ridges.

Strip Flashing: Pieces of membrane material that are used to flash metal flashing flanges such as gravel stop. Also referred to as Stripping.

Strip Mopping: Hot bitumen applied in parallel bands.

Strip Shingles: Asphalt shingles that are manufactured in strips.

Styrene: A colorless oily liquid, C6H5CH:CH2, the monomer for polystyrene.

Styrene Butadiene Styrene (SBS): The modifying agent used in SBS modified asphalt roofing materials that gives the material a rubber like quality.

Substrate: The surface that the roof is installed upon.

Sump: A depression around roof drains and scuppers to help promote roof drainage.

Surface Erosion: The effect on a surface after being worn away from abrasion or weathering.

Surface Texture: The final appearance and quality of an SPF surface. SPF surface textures will be one of the following: Orange Peel Surface Texture, Coarse Orange Peel Surface Texture, Smooth Surface Texture, Verge of Popcorn Surface Texture, Popcorn Surface Texture, and Tree-Bark Surfaced Texture.

Surfacing: The top-most layer of the roof system designed to protect the system from damage.

Surfactant: Short for “surface active agent.” A soluble compound that reduces the surface tension of liquids, or reduces interfacial tension between two liquids or a liquid and a solid having cationic (positive charge), anionic (negative charge), or non-ionic (no charge) nature. The ingredient in SPF that controls the cell size.

SWRI: Sealant, Waterproofing and Restoration Institute


Tab: The portion of an asphalt shingle that is outlined by the cutouts.

Tapered Edge Strip: Tapered insulation strip used to ease transitions from one substrate elevation to another and to provide slope along roof perimeters.

Tape: See Joint Tape and Splice Tape

Tar (ASTM DEFINITION): A brown or black bituminous material, liquid or semi-solid in consistency, in which the predominating constituents are bitumens obtained as condensates in the processing of coal, petroleum, oil-shale, wood, or other organic materials.

Tar Boil: A small bubble found in the flood coat of an aggregate-surfaced built-up roof; usually the result of trapped moisture vapor. Tar Boils are also known as blueberries or blackberries.

Tear-Off: To remove a roof system down to the structural substrate.

Tear Resistance: A material’s ability to withstand tearing. The test is performed by placing stress on an area of the material where a flaw is located. Tear Resistance is expressed in psi per inch width or kilonewton per meter width.

Tear Strength: The strength necessary to tear a material.

Tensile Strength: The amount of longitudinal pulling stress that a material can withstand before being pulled apart.

Termination: The sealed edges of a roof membrane.

Termination Bar (Term.’ Bar): A bar, usually metal or vinyl, used to seal and anchor the free edges of a roof membrane.

Terne: Sheet iron or steel plated with an alloy of three or four parts of lead to one part of tin, used as a roofing material.

Terra Cotta: A semifired ceramic clay used in building construction.

Thatch Roof: A roof covering made with straw, palms, reeds or other natural growths that are bound together in order to shed water.

Thermal Barrier: Material used in conjunction with polyurethane foam that is designed to inhibit the rise in temperature of the foam during a fire in order to delay the foam’s involvement in the fire. Time ratings for thermal barriers should exceed 15 minutes.

Thermal Conductance (C): A constant, equal to a material’s k-value (Thermal Conductivity) divided by the material’s thickness in inches; used often for materials of composite construction such as insulation. For more information.

Thermal Conductivity (k): The heat energy that will be transmitted by conduction through 1 square foot of 1inch thick homogeneous material in 1 hour when there is a difference of 1 degree Fahrenheit perpendicularly across the two surfaces of the material. The higher the k-value, the lower the R-value. Materials with high k-values are good heat conductors, and conversely.

Thermal Insulation: A material used to reduce heat flow.

Thermal Movement: Movement of a material resulting from temperature changes.

Thermal Resistance (R): The measure of a material’s ability to resist heat flow. The formula for Thermal Resistance is R = L / k where (L) is the material’s thickness and (k) is the material’s Thermal Conductivity constant. The higher a material’s R-value, the better it insulates, and conversely.

Thermal Shock: The damage to a roof resulting from expansion and contraction which are the result of sudden extreme temperature changes. Thermal Shock often occurs when a cold rain shower suddenly cools a roof during a hot day.

Thermal Stress: Stress to a roof system or component caused by expansion and / or contraction from temperature change.

Thermoplastic: (1) adjective Becoming soft when heated and hard when cooled. (2)noun A thermoplastic resin, such as polystyrene or polyethylene.

Thermoset: A material that cannot be reshaped or formed by heating. EPDM and Butyl are thermosets.

Thinners: Liquids that are used to reduce a material’s viscosity when mixed but that evaporates during cure.

Thixotropy: Property of certain materials which liquefy when they are subjected to vibratory forces such as simple stirring or shaking and then solidify when left standing.

Throat: (1) The cutout of a shingle. (2) The narrowing passage located between a fireplace and smoke chamber or flue.

Through-Wall Flashing: A material that extends through a wall and is used to direct water entering a wall cavity to the exterior of the structure.

Tie-In: The joining of two different roof systems.

Tie-Off: A watertight seal used to terminate roof membranes at system adjuncts, terminations, flashings, or substrates. Can be temporary (see Night Seal) or permanent.

TIMA: Thermal Insulation Manufacturers Association

Toggle Bolt: A bolt with a separate toggle end that can be flattened to fit through a pre-drilled hole and that springs outward to provide securement when the bolt is tightened.

Tongue and Groove: Premanufactured materials with a convex “tongue” on one side and a concave “groove” on the other so that pieces of material can be joined together by placing the tongue of one piece into the groove of an adjacent piece so that the pieces fit more securely together.

Torque: Force applied to an object, particularly, to screw a mechanical fastener into a roof deck or substrate.

TPA: Tri-Polymer Alloy.

Traffic: Any rooftop activity that can potentially damage the roof surface.

Transverse Seam: The joint between the top of one metal roof panel and the bottom of the next panel, which runs perpendicular to the roof slope.

Treebark Surface Texture: An SPF surface deemed unacceptable for coating. This surface texture has deep valleys and is similar in appearance to rough tree bark.

Tuck Pointing: To remove old and deteriorated mortar from between masonry blocks and replace it with new mortar.


U-Value: The overall coefficient of heat transfer of an assembly measured in BTUs per square foot, per degrees Fahrenheit difference in temperature per hour.

UBC: Uniform Building Code.

UL: Underwriters Laboratories, Inc.

UL Label: A label that has been stamped on certain materials by authority of Underwriters Laboratories, Inc. indicating that the material has met certain performance criteria.

Ultraviolet Light (UV): A form of luminous energy occupying a position in the spectrum of sunlight beyond the violet, and having wavelengths that do not enter the visible spectrum. UV rays accelerate deterioration of roof materials. Hence, the need for protective coatings.

Underlayment: A material installed over the roof deck prior to the application of the primary roof covering. Usually consists of fifteen (15#) or thirty (30#) pound organic felt but can also be self-adhering such as an ice and water protection membrane.

Underwriters Laboratories (UL): A non-profit agency which functions as the testing arm of the National Board of Fire Underwriters. It maintains laboratories for the examination and testing of various devices, systems, and materials to determine their safety against the hazards of fire, wind, and accidents.

Uplift: See Wind Uplift

Upside Down Roof: See Protected Membrane Roof


Valley: The internal intersection of two sloping roof planes that runs from the eaves to the ridge. This intersection collects the most water run-off. See Open Valley, Closed Valley and Woven Valley

Vapor Migration: The natural movement of water vapor from regions of higher vapor pressure to regions of lower vapor pressure.

Vapor Pressure: The pressure at which a liquid and its vapor are in equilibrium at a definite temperature.

Vapor Retarder: A material used to restrict the passage of water vapor through a roof assembly.

Veneer: Any of the thin layers of wood glued together to make plywood.

Vent: An opening or device used to permit air or vapors to exit an enclosed structure.

Ventilation Short Circuit: The disruption of air flow in an intake-exhaust ventilation system. For instance, if vents such as turbine vents or gable vents are placed in between the intake vents and exhaust vents (such as soffit and ridge vents) then the draw created by the Stack Effect will be disrupted and the ventilation system will be much less effective.

Ventilator: A device that circulates fresh air and expels stale air.

Verge of Popcorn Texture: A rough surface texture of Sprayed Polyurethane Foam generally considered unsuitable to receive a base coating. Nodules on this surface are larger than the valleys and an additional 50% or more of coating material is necessary to properly cover and protect the surface. Photos?

Vermiculite: One off a group of micaceous hydrated silicate minerals related to the chlorites and used in lightweight insulating concrete.

Viscosity: The resistance of a material to heat flow.

Viscous: Having a fairly high resistance to heat flow.

Void: An open space or a break in continuity; a gap.

Volatile: That which readily vaporizes; evaporates quickly.

Vulcanize: To improve the strength, resiliency, and freedom from stickiness and odor of rubber, for example, by combining with sulfur or other additives in the presence of heat and pressure.


Water Absorption: The increase in weight of a test specimen expressed as a percentage of its dry weight after being immersed in water for a specified time at a given temperature.

Water Cure: To control the rate of cure of materials such as concrete by spraying a fine mist of water on the surface.

Water Cut-off: See Night Tie-Off.

Water Guard: A turned up edge on valley metal or continuous wall flashing; used to prevent water migration under the roof system.

Water Stop: Material placed over a joint and used to prevent water entry.

Waterproof: Being resistant to moisture infiltration.

Waterproofing: The treatment of a surface or structure in order to prevent the passage of water under hydrostatic pressure.

Water Trough: The area in a valley where water runs. Usually referred to with open valley configurations.

Weather: To undergo degradation in quality and appearance which is caused by exposure to the sun, wind, rain, etc.

Weep Holes: Small holes used to permit moisture to drain that has gathered inside a building component.

Weld: To join multiple metal or PVC components together by heat fusion.

Wet Bulb Temperature: Air temperature in ° F as measured by a thermometer with a bulb covered by a damp wick.

Wet Film Thickness: The thickness of an uncured material such as a coating.

Wick: To convey liquid by capillary action.

Wind Clip: A clip that slips over the ends of tile, slate and other steep slope roofing materials in order to help prevent wind uplift damage.

Wind Load: The force that wind puts on structures.

Wind Uplift: (1) The upward displacement of a section of a roof system or component caused by movement of air from a location of higher air pressure, such as inside a building, to an area of lower air pressure, such as the surface of a roof during a windy day. Strong wind across the surface of a roof, especially at corners and along perimeters, creates low air pressure above the surface of the roof. Nature will automatically try to compensate for this by moving air from an area of higher pressure such as inside a building. If all penetrations and perimeters are not properly sealed, then “blow-off” can occur. (2) Displacement or blow-off of shingles or other roofing caused by the wind.

Windward: Facing into the wind.

Wire Tie: A system for attaching heavy steep slope roofing materials such as slate r tile by using wire fasteners in addition to or in place of nails.

Woven Valley: A valley construction whereby the valley has a woven look which is effected by overlapping alternate courses of shingles from both sides of the valley.



Z Bar or Z Section: A piece of steel formed in the shape of a “Z.”

Zinc: A bluish-white, lustrous metallic element that is brittle at room temperature but malleable with heating. It is used to form a wide variety of alloys including brass, bronze, various solders, and nickel silver, in galvanizing iron and other metals, for electric fuses, anodes, and meter cases, and in roofing, gutters, flashings, edge metals and also for various household objects. Atomic number 30; atomic weight 65.37; melting point 419.4 °C; boiling point 907 °C; specific gravity 7.133 (25 °C); valence 2.

Written by Damon