Roofing Terminology


Absorption: The act or process of retaining foreign particles such as gas or liquid without transmission of these particles.
Active: Will corrode in the presence of moisture or a “noble” metal.
Adhere: The clinging of one surface to another; either molecularly or otherwise.
Adhesion: The state of adhering
Alligatoring: The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks that resemble an alligator?s hide.
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.
Application Rate: The rate at which a material is applied per unit area.


Back-Nailing: The method of fastening the back or upper side of a ply of roofing felt or other component in a roof system so that the fasteners are covered by the following ply.
Bird Bath: Small, inconsequential amounts of water on a roof that quickly evaporate.
Bleeder Strip: A starter strip placed along rake edges for use in asphalt shingle roofing. See also Rake-Starter.
Blind-Nailing: The use of nails so that they are not exposed to the weather in the finished roofing system. See Back-Nailing
Blister: A pocket of air trapped between layers of felt or membrane. Blisters are usually caused by water or other foreign substances.
Bond: The force(s) holding two components in positive contact.
Bonding Agent: A chemical agent used to create a bond between two layers.
Brake: A piece of equipment used for forming metal.
Bridging: When membrane is unsupported at a juncture.
Brooming: Embedding a ply of roofing material into hot bitumen or adhesive by using a broom, squeegee, or other piece of equipment to eliminate voids and help ensure adhesion.
Buckle: A long, tented displacement of a roof membrane. Can occur over insulation and deck joints.
Bundle: An individual package of shingles or shakes.


Calender: A machine used to laminate sheeting or for applying coating with a specified thickness and/or surface attribute.
Calendering: A specific process used to manufacture some membranes such as PVC.
Cant: (1) Short for Cant Strip; (2) The act of installing foam at a right angle adjunct.
Cant Strip: A triangular-shaped strip of material used to ease the transition from a horizontal plane to a vertical plane. Cant strips can be made of wood, wood fiber, perlite, or other materials.
Cap Flashing: A material used to cover the top edge of base flashings or other flashings. (See also Coping.)
Cap Sheet: A granule-surfaced membrane often used as the top ply of BUR or modified roof systems.
Capacitance Meter: A device for locating moisture within a roof system by measuring the ratio of the change to the potential difference between two conducting elements that are separated by a non-conductor.
Catalyst: A substance that effects a chemical reaction and/or the rate at which a chemical reaction takes place. In roofing, catalysts are used in SPF roofing.
Cathodic: metals low in the Galvanic Series.
Cavitation: The vaporization of a liquid under the suction force of a pump which can create voids within the pump supply line. Cavitation will result in off-ratio foam in Sprayed Polyurethane Foam applications.
Chalk: A powdery residue on the surface of a material.
Chalk Line: (1) A string on a reel in a container that can hold chalk; (2) A line made on by pulling taut a string coated with chalk and snapping it.
Chemical Resistance: A materials ability to retain its properties when it comes into contact with certain chemicals.
Cladding: A material used to cover the exterior wall of a building.
Cleat: A continuous metal strip used to secure two or more metal roof components together. Commonly used along with coping or gravel stop on tall buildings.
Clip: A small cleat. See Cleat.
Closed-Cut Valley: A method of valley application in which shingles from one side of the valley extend across the valley while shingles from the other side are installed over the top of those and then trimmed back approximately 2 inches from the valley centerline.
Closure Strip: A material used to close openings created by joining metal panels or sheets and flashings.
Coarse Orange Peel Surface Texture: A surface showing a texture where nodules and valleys are approximately the same size and shape. This surface is generally acceptable for installing a protective coating.
Coating: A layer of material that is spray, roller, or brush applied over a surface for protection or sometimes decoration.
Cohesion: Mutual attraction by which the elements or particles of a body or substance are held together.
Coil Coating: The application of a finish to a coil of metal or other material.
Cold Forming: The process of shaping metal into desired configurations at ambient room temperature.
Cold Process Built-Up Roof: A roof consisting of multiple plies of roof felts laminated together with adhesives that usually come right out of a can or barrel and require no heating.
Combustible: Capable of igniting and burning.
Concealed-Nail Method: A method of installing asphalt roll roofing material in which all nails or fasteners are driven into the underlying roofing and covered by an overlapping course.
Condensate: The liquid resulting from condensation.
Condensation: The conversion of water vapor to liquid state when warm air comes in contact with a cold surface. (See also Dew Point.)
Conduction: The transmission or conveying of something through a medium or passage, especially the transmission of electric charge or heat through a conducting medium without perceptible motion of the medium itself.
Coping: the piece of material used to cover the top of a wall and protect it from the elements. It can be constructed from metal, masonry, or stone.
Counter Batten: Wood strips installed vertically on sloped roofs over which horizontal battens are secured.
Course: (1) The term used for each row of roofing material that forms the roofing or flashing system; (2) One of multiple layers materials applied to a surface. For example, a three-course flashing consists of a layer of mesh or other reinforcing material sandwiched between two layers roofing cement.
Cove: In roofing, a heavy bead of sealant material installed at the point where vertical and horizontal planes meet. It is used to eliminate the 90? angle. See also Fillet.
Cover Plate: A metal strip sometimes installed over the joint between formed metal pieces.
Coverage: The surface area covered by a material.
Crack: A separation or fracture occurring in a material. See also Split.
Cream Time: Time in seconds at a given temperature when the A and B (isocyanate and resin) components of SPF will begin to expand after being mixed.
Creep: Movement of roof membrane causing the roof system to be deformed
Cross Ventilation: The effect of air moving through a roof cavity between vents.
Cure: A process by which a material is forms permanent molecular linkages by exposure to chemicals, heat, pressure, and/or weathering.
Cure Time: The time necessary to effect curing.
Curing Agent: A material additive that alters chemical activity between the components resulting in a change in the rate of cure.
Curing Compound: A liquid that is applied to newly installed concrete which slows water loss while curing.
Cut-off: A detail designed to seal and prevent lateral water movement in an insulation system, and used to separate different sections of a roofing system.
Cutout: The open area between shingle tabs. Also known as a “throat”.


Dampproofing: Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.
Dead Level: Refers to a roof with no slope or pitch.
Dead Loads: Permanent, non-moving loads on a roof resulting from the weight of a building?s components, equipment, and the roof system.
Deflection: The downward displacement of a structural member under load.
Degradation: A decline in the appearance, structure, or properties, of a material or substance.
Delamination: Separation of laminated layers of a material or system.
Dew Point Temperature: The temperature at which water vapor turns to liquid in cooling air at the existing atmospheric pressure and vapor content.
Diffusion: The movement of a substance such as water vapor from regions of high concentration to regions of lower concentration
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.
Double Coverage: Installing roofing so that there is twice the materials used resulting in a double layer of roofing.
Double Graveling: Installing one layer of gravel in a flood coat of hot bitumen, removing the excess gravel and then installing a second layer of gravel in another flood coat of hot bitumen.
Dry Bulb Temperature: The temperature of air in degrees Fahrenheit measured by an ordinary thermometer.
Dry Film Thickness: The thickness in mils (thousandths of an inch), of a dried coating or mastic.
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: Wood rot caused by certain fungi. Dry rot can result from condensation build-up, roof leaks that go untended, or from other problems. Dry rot will not remain localized. It can spread and damage any lumber touching the affected area.
Dynamic Load: Any moving load on a roof such as people and equipment. Wind can also be considered a Dynamic Load.


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


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
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.
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 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.
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.
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.
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 Collar: (sometimes referred to as a roof jack or flashing boot) an accessory flashing used to cover and/or seal soil pipe vents and other penetrations through the roof.
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.
Flood Test: A water test performed to determine the effectiveness of a roof covering.
Flow: To become fluid in character.
Froth Pack: A term used to describe small, disposable aerosol cans of SPF.


Galvanic Action: A reaction between different metals in the presence of an electrolyte.
Galvanize: To coat with zinc.
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.
Grain: A unit of measure for the mass of moisture: a unit of weight equal to 0.002285 ounces or 0.036 dram.


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


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.
Interlayment: A waterproof material usually installed between adjacent rows of wood shakes to help with the roof?s waterproofing characteristics.
Internal Pressure: Atmospheric pressure inside a structure that correlates to the number and location of openings and air leaks.


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.
Lap: The part of the roofing material that overlaps a section of adjacent material.
Lap Seam: Where two material that overlap are sealed together.
Live Loads: Temporary items on a roof such as equipment, people, snow, etc. which the roof must be designed to support.


Masonry: Refers to bricks, concrete, or concrete blocks.
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.
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.
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
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.


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.
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.
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 (s?.)
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.
Noble: In reference to metal, inert or inactive.


Orange Peel Surface Texture: A surface with a texture comparable to the skin of an orange upon which a protective coating may be applied.
Overspray: The loss of spray particles (from coatings, SPF, etc.) in the air.


Pallet: A platform used to hold materials.
Penetration: Any object that pierces the surface of the roof.
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.
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.
Pinhole: A small hole in a coating, foil, membrane, or other roofing material.
Pitch: Term used to describe Roof Slope and also short for Coal Tar Pitch.
Pitch Pocket (aka, 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, click here.
Pittsburgh Lock Seam: A method of interlocking two separate pieces of metal.
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.
Ponding: The accumulation of water at low-lying areas on a roof.
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.
Press Brake: A mechanical device used to form sheet metal into desired shapes and profiles.
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.
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.


Racking: The method of installing asphalt shingles where the shingles are installed straight up to the ridge rather than horizontally. If this method is used with 3-tab shingles, the throats of every other course will line up.
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. For a picture, click here.
Rake-Starter: A starter strip placed along rake edges for use in asphalt shingle roofing. See also Bleeder Strip.
Re-Cover (Overlay): The installation of a new roof system over an existing system without removing an existing system. For some hints on recovers, click here.
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.
Ridging: The formation of a Buckle.
Roll Goods: The term used for all roofing materials that come in rolls.
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 Jack: a metal or wood bracket used to support toeboards on steepslope roofs. (also see Flashing Collar.)
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, click here.
Run: The horizontal dimension of a slope.
Rust Blush: Early stage of rust indicated by an orange or reddish color.


Sag: Settling or drooping of base flashings that have not been properly secured to a surface.
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.
Seam: A line, ridge, or groove formed from fitting, joining, or lapping two sections together.
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.
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 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.
Side Lap: The longitudinal overlap of neighboring materials.
Single Coverage: One layer of roofing material.
Single-Lock Standing Seam: A standing seam system with one overlapping interlock between two seam panels.
Slag: Residue from blast furnaces that is sometimes used for the surfacing on aggregate-surfaced built-up roof systems.
Slating Hook: A hook-shaped device used to secure roofing slate.
Slit Sample: A cut made in SPF roofing to measure coating thickness. The cut should be about 1.5″ long by ?” deep by ?” wide.
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 Load: A roof load resulting from snowfall. Snow load is a major structural consideration when roofs are designed in areas that receive heavy snow.
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.
Solvent Weld: To weld materials using a liquid solvent.
Spall: A chip, fragment, or flake from concrete or masonry.
Specification: Written requirements for a construction project; contains but is not limited to the following: the scope of work, methods of construction, and materials.
Splice: To join by overlapping along ends.
Split: The separation of a material resulting from tensile forces.
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.
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-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. 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.
Strip Mopping: Hot bitumen applied in parallel bands.
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.


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.
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: A bar, usually metal or vinyl, used to seal and anchor the free edges of a roof membrane.
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, click here.
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. For more information, click here.
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. For more information, click here.
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: adjective; Becoming soft when heated and hard when cooled.
Throat: The cutout of a shingle.
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.
Torque: Force applied to an object, particularly, to screw a mechanical fastener into a roof deck or substrate.
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.


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.


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.
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?
Viscosity: The resistance of a material to heat flow.
Viscous: Having a fairly high resistance to heat flow.
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.
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.
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 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

Be Sociable, Share!
This entry was posted in Roofing Information and tagged , . Bookmark the permalink.