• Alligatoring: Shrinkage cracking of the bituminous surface of built-up or smooth surface roofing, producing a pattern of deep cracks resembling an alligator hide.
  • Asphalt – A dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt may be further refined to conform to various roofing grade specifications
  • Attic – The open space between the underside of the roof sheathing and the upper side of the ceiling directly below the roof.


  • Ballast – Aggregate such as river rock or concrete pavers used as an anchoring material to hold roofing material in place.
  • Base Sheet – A heavy sheet of felt sometimes used as the first ply in built-up roofing.
  • Base Flashing – A. That portion of the flashing that is attached to or rests on the roof deck to direct the flow of water on the roof, or to seal against the roof deck. B. A material applied to the base of a wall extending above a roof, as a protection for the junction of the wall, and the roof.
  • Bitumen – A generic term for asphalt or coal tar pitch
  • Blind Nailing – Shingles nailed in such a location that when the next shingle is applied, the nails of the first shingle do not show.
  • Blister – A spongy raised portion of roofing membrane as a result of pressure of entrapped air or water vapor.
  • Bond – Adherence between elements of the roof system.
  • Boot – A covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc., from around a penetration. Also, a flexible material used to form a closure, sometimes installed at inside and outside corners.
  • Breather – A type of roof vent consisting of a hooded flanged pipe 2″ to 8″ in diameter, penetrating the roofing membrane to allow escape of moisture from insulation
  • Buckling – Warping or wrinkling of the roof membrane.
  • Built-up Roofing (BUR) – A continuous semi-flexible roof covering consisting of laminations or plies of saturated or coated felts alternated with layers of bitumen


  • Cant or Cant Strip – A beveled or triangular-shaped strip of wood, insulation, or other material designed to serve as a gradual transitional plane between the horizontal surface of a roof deck and a parapet wall or other vertical surface. Cants are NOT required by Duro-Last, and when possible should be removed.
  • Cap Flashing – Portion of flashing built into a vertical surface to prevent the flow of water behind the base flashing. The cap flashing overlaps and caps off the top of the base flashing.
  • Caulking – The physical process of sealing a joint or juncture, or sealing and making weather-tight the joints, seams or voids between adjacent surfaces by filling with a sealant.
  • CDR Ring – Composite Drain Ring. A pair of rings made of a composite material used as a compression water cut-off in the Duro-Last drain boot. See detail 2020 and data sheet.
  • Cement Asphaltic Plastic – A mixture of asphalt, solvent and mineral stabilizer used to adhere flashings or to fill pan flashings.
  • Closed Valley – A valley where the flashing is covered by shingles.
  • Chalk Line – A line made on the roof or other flat surface by snapping a taut string or cord dusted with colored chalk.
  • Cleat – A continuous metal strip or angled piece, used to secure metal components.
  • Clip – A non-continuous metal component or angle piece used to secure two or more metal components together..
  • Closed Curb Flashing – A curb flashing that is custom fabricated at the factory using Duro-Last membrane. It is made to slide over the top of the curb frame and flash (waterproof) the four sides of the curb. Closed flashings are welded to the deck sheet and terminated at the top.
  • Coal Tar Pitch – A bituminous material produced by distilling crude tar residue derived from the cooking of coal. It is used as the waterproofing material for tar and gravel built-up roofing.
  • Concealed Nailing – Application of roll roofing in such a manner as to conceal or cover all nail heads used to fasten the roofing to nail able decks.
  • Condensation – The change from water vapor to liquid water, resulting from a drop in temperature of an air vapor mixture.
  • Conductor – A pipe for conveying rainwater from a roof gutter to a drain or from a roof drain to a storm drain.
  • Coping – The cap or highest covering course of a wall, usually overhanging the wall and having a sloping top to carry off water.
  • Counter Flashing – Strips of metal, roofing, or fabric inserted and securely anchored to the regle or attached to a vertical surface above the plane of the roof and turned down over the face flashing to protect the base flashing.
  • Course – Row of shingles that can run horizontally, diagonally or vertically
  • Combustible – Capable of burning.
  • Compatible Materials – Two or more substances that can be mixed, blended, or attached without separating, reacting, or affecting the materials adversely.
  • Concrete Nails – A nail specially designed for installation into concrete. For Duro-Last installations, pre-drill the concrete deck with a 3/16″ masonry bit a minimum of 1½” deep to seat the concrete nail a minimum 1” deep. See data sheet.
  • Concrete Screw – A square drive, #14 screw with high-low threads, specially designed for installation into concrete. For Duro-Last installations, pre-drill the concrete deck with a 3/16″ masonry bit a minimum of 1½” deep to seat the concrete screw a minimum 1” deep.
  • Contractor Responsibilities – The contractor is responsible for following all applicable plumbing, building, electrical and safety codes, using standard roofing practices and proper safety procedures, and following OSHA guidelines. The contractor must also assure that the installed system meets or exceeds all project specifications as well as all local and other safety rules, regulations, and codes.
  • Coping Cap – The covering piece on the top of a parapet wall, usually made of metal, masonry, or stone.
  • Core Cuts – A series of sample cut outs that are taken through the existing roof, typically down to the roof deck. Core cuts determine the thickness, moisture, and make up of the existing roofing assembly, as well as the type and length of fastener to be used.
  • Core Cutter – A tool used to make core cuts into the existing roof assembly. May be purchased through the Duro-Last sales department.
  • Corners – Drip Edge & Gravel Stop – Duro-Last extruded 2″ & 4″ drip edge and gravel stop corners are mitered at 90° and are available in outside corners only.
  • Crack – A break in a roofing membrane as a result of flexing, oven occurring at the ridge or wrinkle
  • Cracking – After long exposure, a fissure or fissure pattern appearing on the shingle of roofing due to weathering of the asphalt
  • Curb – A wall of wood or masonry built above the level of the roof, surrounding a roof opening such as for installation of roof fans or other equipment.
  • Canted Curb – A curb or frame that is placed over an opening through the roof to support equipment such as air conditioners or other large units. If the curb or frame has a beveled 45-degree cant, it is called a “canted curb.” Order a Duro-Last curb flashing with a 12″ skirt to accommodate the canted curb.
  • Cure – A process whereby a material forms permanent molecular linkages by exposure to chemicals, heat, pressure and/or weathering.


  • Data Sheet – Provides a detailed description of the product and lists basic uses and installation guidelines.
  • Dead Load – The total weight of all installed materials and the constant weight of a roof used to compute the strength of all supporting framing members.
  • Deck/Roof Deck – The structural component of a roof that provides the substrate to which the roofing or waterproofing system is applied.
  • Dormer – A separate smaller roofed structure that projects from a sloping roof to provide more space below the roof and to accommodate a vertical window.
  • Downspout – A pipe conveying rainwater from a roof gutter to a drain.
  • Drip Edge – A modified L-shaped flashing used along the eaves and rakes. The drip edge directs runoff water into the gutters and away from the fascia.
  • Drain: An outlet on the roof used to collect and direct the flow of runoff water from a roof area.
    • 2-Inch Adapter Drain is a drain flashing made with a 1/4″ washer welded to a Duro-Last skirt used on drains that are 2″ or less
    • Drain Boot with CDR Rings is an inverted stack flashing made of Duro-Last membrane material designed to line the pipe, and 2 composite (compression) rings that are used inside the drain for water cut-off. Caulk is used between the drain and the drain boot at the point where the CDR rings will be fitted. Once the CDR rings are in place inside the drain boot, the strings are cut to give compression, preventing water from backing in under the system.
  • Drill Bit / SDS – A drill bit with a titanium carbide tip and a Slotted Drill Shank (SDS). Typically used with a hammer drill.


  • Eave – The horizontal roof overhang that extends outward and is not directly over the exterior walls or the building’s interior
  • Edge Details – Rigid edge terminations that help make rooftop perimeters watertight.
  • 2″ & 4″ Drip Edge is made from rigid, extruded vinyl, and has an attached 6″ skirt. It is fastened 8″ on center to the deck or wood nailer with approved fasteners and the skirt is heat-welded to the field membrane. Drip edge can be installed on any flat edge including the top of the parapet wall.
  • 2″ & 4″ Gravel Stop is made from rigid, extruded vinyl, and has an attached 6″ skirt. It is fastened 8″ on center to the deck or wood nailer with approved fasteners and the skirt is heat welded to the field membrane. Gravel stop can be installed on any flat edge including the top of the parapet wall. Kynar coated metal Duro-Cap covers are also available on request.
  • Fascia Bar 1 ¾” “& 4” with Cover is made from rigid, extruded vinyl. It is fastened 6″ on center and may be used as perimeter detail and as termination on any square or rectangular penetration. Kynar coated metal Duro-Cap covers are also available on request.
  • Termination Bar is a ridged, extruded vinyl termination bar and shall be fastened 6″ on center to the deck or wood nailer with approved fasteners. Termination bar may be used as perimeter detail and as termination on any square or rectangular penetration.
  • Elk – Shingle manufacturer based out of Texas, provides elegant and innovative shingles.
  • End Lap – The amount of overlap at the end of a ply on the application of roll roofing.
  • Encapsulate – To enclose or wrap with membrane.
  • EPDM – A synthetic rubber sheet used in single ply roof membrane (ethylene propylene diene monomer)
  • Expansion Joint – A planned, controlled joint placed between two roof surfaces or between two sections of a built-up roof. Expansion joints allow roofs to expand without causing harm to building.
  • Exposure – Portion of shingle that is exposed to the weather


  • Face Nailing – Nailing with the nails placed in the exposed area or face of the shingle.
  • Fascia – A wood trim board used to hide the cut ends of the roof’s rafters and sheathing. The gutter system is usually nailed to the fascia
  • Felt – A very general term used to describe roll roofing materials, consisting of a mat of organic or inorganic fibers.
  • Felt (15 & 30) – Asphalt or coal tar saturated felt weighing approximately 15 or 30 pounds per 100 square feet.
  • Fire Wall – Any wall built for the purpose of restricting the spread of fire in a building. Such walls of solid masonry or concrete usually divide a building from the foundations to about a meter above the roof.
  • Fire-Resistant – Material that is resistant to catching on fire.
  • Fish Mouthing – The raising of a portion of the butt edge (lower edge) of a shingle. This curved short section tapers back into the shingle. Usually, only the front part of the shingle is affected. Often the result of moisture absorption followed by moisture evacuation in the shingle.
  • Fire Rating – UL Standards for External Fire Testing for Roof Coverings (UL 790). The requirements cover the performance of roof covering materials exposed to fire conditions originating from sources outside of buildings on which the coverings are installed. The UL 790 rates roof coverings as having a Class A, B, or C fire ratings.
  • Flashing (eaves) – Treatment of the edge of a roof with metal.
  • Flashing – Metal strips used to form a watertight seal between the items butted up against the shingles. Flashing is used along walls, chimneys and dormers. Metal is usually 28 gauge galvanized sheet metal, but may be lead, copper, tin or aluminum.


  • Gable – The triangular end of an exterior wall from the level of the eaves to the ridge of a double-sloped roof.
  • GAF – Shingle manufacturer based in New Jersey. Have been in business since the l886, GAF has a wide variety of shingle styles and colors.
  • Gambrel Roof – A type of roof which has its slope broken by an obtuse angle, so that the lower slope is steeper that the upper slope. A double-sloped roof having two pitches.
  • Grande – Elk’s newest shingle offering. More than40% bigger than standard shingles. Has a 90 mph wind warranty.
  • Gravel Stop – A gravel guard used at the rakes and eaves of a built-up gravel coated roof.
  • GripPull – A stand-up tool with Visegrips and pulleys, used to pull wrinkles out of the Duro-Last deck sheet during installation.
  • Gutter – A channeled metal component installed along the down slope perimeter of a roof to convey runoff water from the roof to drain leaders or downspouts.


  • Half Sheet – Also known as a “half tabs” or “28” laps.”
  • Header – The beam into which the common joists are fitted when framing around a roof opening.
  • Head Lap – The overlapping of shingles or roofing felt at their top edge
  • Heat Welding – A hot air process where two separate pieces of material are welded together.
  • High Risk Roof – A roof which scores 15 or greater out of 20 using the Snow Overload Risk Assessment checklist
  • Hip Roof – A roof, which rises by inclined planes from all four sides of a building. The line where two adjacent sloping sides of a roof meet is called the hip.
  • Hot Air Weld – See field weld.
  • HVAC Units – Heating, ventilation, and air conditioning equipment


  • Insulation – Material such as poly-isocyanurate, or expanded or extruded polystyrene, used under the roof membrane to prevent the passage of heat. An appropriate separator sheet must be used when installing Duro-Last membrane over incompatible insulation.


  • Lap Cement – A cut back asphalt used for cementing the laps of roll roofing.
  • Lap – The distance between factory welds on a deck sheet.


  • Mastic – A tape like sealant used as water block.
  • Membrane – A saturated cotton or burlap fabric used for certain built-up roofing applications. Also a waterproofing system or roof covering
  • Mil – A unit of measure. One mil is equal to 0.001 inches, or 25.4 micrometers. Often used to indicate the thickness of a roofing membrane
  • Moisture Relief Vent – A venting device installed through the Duro-Last roofing membrane to relieve moisture vapor pressure from within the roofing system.
  • Modified Bitumen – Asphalt with the addition of polymer modifiers to increase cold temperature flexibility and warm temperature
  • Monolithic – Formed from or composed of a single material; seamless.


  • Nailer – Also known as blocking, a piece or pieces of dimensional lumber and/or plywood secured to the structural deck or walls, providing a receiving medium for fasteners used to attach membrane or flashing.
  • Nailing Strips – Strips of wood placed at the eaves of all types of roof decks except wood, and at the tops of masonry expansion or ventilation curbs for attaching the flashing. Also called nailers.
  • Night seal or Night tie-in – Materials and/or methods used to temporarily seal a membrane edge during construction to protect the uncompleted roofing assembly from water penetration. Usually removed when roofing application is resumed


  • Open Curb or Stack Flashing – A curb or stack flashing made to be wrapped around a roof curb or pipe stack and must be welded closed and welded to the deck sheet and then terminated at the top. Open curbs are produced with an additional 3″ of membrane for vertical field welding the item closed
  • Open Valley – A valley where the flashing is exposed to the weather (NOT A GOOD PRACTICE)
  • Overhang – That portion of roofing extending beyond the deck. As related to the roof structure, that part of the roof structure which extends beyond the exterior walls of a building


  • Parapet Wall – The part of a perimeter wall that extends above the roof.
  • Parapet Wall Flashing – A custom made flashing for a wall on a roof with fastening tabs spaced 28″ or less.
  • Penetration – A measure of the viscosity of a bitumen.
  • Penetration – Any construction such as pipes, conduits, and HVAC supports that pass through the roof surface.
  • Pitch – Height from the joist to ridge divided by rafter length, which translates to rise in inches per horizontal foot or ratio of pitch. Ratio is an portion up to full pitch (24″ in 12″).
  • Pitch Pan or Pocket – Usually a rectangular flanged metal collar placed around metal supports that project above a roof deck. The pitch pan is placed on top of the roofing underlayment.
  • Pipe Flashing / Round Flashing – Custom made flashing, either open or closed and used for round roof penetrations such as vent and soil pipes. Duro-Last will prefabricate custom rounds up to 999 inches in diameter.
  • Ply – A single layer or thickness of roofing material. Built-up roofs are described as three, four ply, etc., according to the number of layers used to build up the membrane.
  • Polyglass TU Plus – Self-adhered Modified Rubber Tile and Metal underlayment. This membrane is glass fiber reinforced, with a high strength polyester fiber fabric on the upper surface.
  • Ponding – The collecting of water in shallow ponds on the top surface of roofing. Certain roofs are designed for the ponding water to a shallow depth over the whole surface of the roof deck, to aid in summer cooling. Many flat roof systems void their warranties if ponding water sits on the deck for more than 48hrs.
  • Positive Drainage – Slope that has been designed into a roof area to ensure drainage within 48 hours after the end of rainfall, when conditions are conducive to drying.
  • Primer – A cut back asphalt coating of thin consistency used on concrete or metal preparatory to applying a built-up roof.
  • Purlin – Boards laid from gable to gable on which the common rafters sit.
  • Pre-Fabricate – To make or pre-assemble custom sized roof deck sheets and accessories at the Duro-Last factory under optimal, quality-controlled conditions. About 80% of Duro-Last welds are done at the factory under ideal conditions.
  • Pull Test – A test of a fastener using a Pull Tester on a deck/substrate to determine the fastener spacing for a roof installation. The less the pull, (measured in pounds of resistance) the greater the quantity of fasteners that will be needed along the deck sheet fastening tab. The greater the pull, the fewer fasteners that will be needed. Consult the Duro-Last Specification Manual to calculate the proper fastening spacing along the fastening tab (not to exceed 18” on center).
  • Pull Tester – Tool that measures the pounds of pull-out resistance on a Duro-Last approved fastener
  • PVC – A generic Term for single ply plastic sheet membrane (poly vinyl chloride)


  • Rafters – The lumber supports that make up the roof structure. Usually 2″ x 12″ lumber. The roof sheathing is nailed to the rafters.
  • Reglet – A groove in the vertical wall adjacent to a roof surface, above the top of base flashing into which the metal counter flashing is placed and rigidly held in place; it is either formed in concrete or consists of a metal insert
  • Ridge – The horizontal line where two opposite sloping sides of a roof join at the highest point of the roof, hip, or dormer. On double sloped gable roofs sometimes called the comb.
  • Ridge Cap – Formed shingles, shake or tile used to cover the ridge of a building. Make sure that specially designed cap products are used. Many roofers will use materials not made for this purpose.
  • Roll Roofing – Any roofing material, which comes from the dealer in rolls. More specifically it applies to mineral surfaced asphalt, or composition roofing.
  • Roll Roofing (granule surfaced) – Roll roofing finished on one side with colored granules.
  • Roll Roofing (smooth surfaced) – Roll roofing which is coated on both sides with either a smooth or veined surface.
  • Roof System – A system of interacting roof components, generally consisting of a membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building’s thermal resistance.
  • Roof Trak II Walkway Pads – A non-skid walkway pad for rooftop protection in heavily traveled areas such as around large units that require service.
  • Roof – A protective covering that covers or forms the top of a building.
  • Roof Drain – The termination or fitting at the roof of an interior drain or leader for draining rainwater from normally flat roofs.
  • Roof Insulation – Any medium or low density material used as part of the roofing system to reduce heat loss through the roof. A variety of insulation materials are being used including wood fibers, glass fibers, cork, plastics and poured lightweight.
  • Roof Span – Distance from outer wall to opposing outer wall of a building covered with a roof.
  • Run – The horizontal distance between the face of a wall and the ridge of the roof.


  • Saturated – Soaked or filled with moisture. A core sample of an existing assembly is considered saturated when droplets of moisture can be squeezed from the sample.
  • Scupper – An outlet in the wall of a building or a parapet wall for drainage of overflow water from a floor or roof directly to the outside. Special scupper drains connected to internal drains are also sometimes installed at roof and wall junctions.
  • Self-Healing – A term used in reference to bitumen which melts with the heat from the sun’s rays, and seals over cracks that earlier formed in the bitumen from other causes
  • Separator – Term used to describe the means of keeping two non-compatible materials from coming into contact with each other.
  • Side Lap – The horizontal distance one shingle overlaps adjacent shingle in the same course; also the horizontal distance one sheet of roofing overlaps adjacent sheet.
  • Single Coverage – Method of applying roof shingles to provide only one complete layer of roof protection. Many special shingles for re-roofing are designed for single coverage for reasons of economy.
  • Single-Ply Membranes – Roofing membranes that are field applied using only one layer of membrane material (either homogeneous or composite) rather than multiple layers.
  • Skirt – Membrane material attached to an accessory, such as curbs, stacks, drip edge, gravel stop, drains etc. This skirt is used for overlapping onto a deck sheet for the purpose of field welding a watertight assembly.
  • Sky Light – Glass opening in roof to admit light.
  • Slateline – GAF shingle made to mimic conventional slate roofing, a highly attractive shingle with a pronounced shadow effect.
  • Slope – The ratio between the measures of the rise and the horizontal span
  • Soffit – A board or sheet that extends from the fascia to the buildings siding and hides the bottom of an overhang. Soffit may or may not contain ventilation slots depending on the attic venting system used.
  • Starter Course – The first course of shingles installed on a roof, starting at the lower left edge of the eave.
  • Step Flashing – Metal shingles or plates used in a stair-step pattern under regular shingles. Step flashing is the recommended flashing whenever a wall or chimney is above the roof line.


  • Tab – Weather exposure surface of a shingle between the cutouts.
  • Termination – The method of anchoring and/or sealing free edges of the membrane in a roofing or waterproofing system
  • Tie-In – The transitional seal used to terminate a roofing or waterproofing application at the top or bottom of flashings or by forming a watertight seal with the substrate, membrane, or adjacent roofing or waterproofing system.
  • Truss – A combination of members such as beams, bars and ties, usually arranged in triangular units to form a rigid framework for supporting loads over relatively long spans as in wide span roof construction.


  • UV / Ultraviolet – Invisible light radiation, adjacent to the violet end of the visible spectrum, with wavelengths from about 200 to 400 nm. (nanometers).
  • Underlayment – A sheet material that is used to separate the roof deck and the roof system


  • Valley – The horizontal line formed along the depressed angle at the bottom of two inclined roof surfaces.
  • Vapor Barrier – A material that prevents the passage of water or water vapor through it.
  • Velux – One of the world leaders in skylight manufacturing. Uses all glass skylights instead of plastic bubbles that are common in the industry today
  • Vent – An outlet for air; vent pipe in a plumbing system; a ventilating duct.
  • Vent Pipe – A vertical pipe providing an escape for foul gasses from a sanitary fixture. For a number of fixtures the vent pipes lead into a larger vertical pipe to the outside through the roof called a vent stack.


  • Waterproof – The quality of a membrane, membrane material, or other component to prevent water entry.
  • Wind Load – Force exerted by the wind on a structure or part of a structure.
  • Water Vapor – Moisture as a gas in air. Warm air can hold more water vapor than cold air. Water vapors in the air crates a pressure much like any other gas. Cold air has a relatively low vapor pressure.
  • Wind Requirements – Duro-Last has special fastening requirements for roofs 40’ and over and roofs in high wind zones. The Duro-Last Engineering Services department can perform wind calculations using ASCE-7, which determines fastening patterns for roofs in high wind zones considering the building’s height, location, wind zone, pull tests, wall heights etc.
  • Wind Tab – A fastening tab that must be located 24” to 36” from a parallel exterior edge or wall when the wall is 24” or less in height. Normally a 31” reverse tab (or series of 31” reverse tab) is used as a wind tab. See 31” reverse.
  • Wind Uplift – The force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface.
  • Wrinkle – A slight ridge caused by folding, rumpling or creasing. In roofing usually refers to the common wrinkle pattern that forms over the joints or insulation.
  • Wood Nailer – #2 grade lumber or better is required as a hard surface for edge fastening in any situation where 1-inch or greater of insulation is added to the roof perimeter edge.