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Job-Average Basis: A Technique for determining the average dimensions or quantities of materials, by analysis of roof test cuts. The technique requires a minimum of three test cuts per roof area, plus one cut for each additional 10,000 square feet of roof area. Job-average basis is computed by dividing the sum of all measurements take by the number of measurements taken. The results would describe the job-average for the quantity dimension.
Knot: An imperfection of non-homogeneity in materials used in fabric construction, the presence of which causes surface irregularities.
Live Loads: Moving roof installation equipment, wind, snow, ice or rain.
Mastic: (See Flashing Cement or Asphalt Mastic)
Membrane: A flexible or semi-flexible roof covering or waterproofing layer, whose primary function is the exclusion of water.
Mesh: The square opening of a sieve.
Metal Flashing: (See Flashing) Metal flashing is frequently used as through-wall flashing, cap flashing, counterflashing or gravel stops.
Mineral Fiber Felt: A felt with mineral wood as its principal component.
Mineral Granules: Opaque, natural, or synthetically colored aggregate commonly used to surface cap sheets, granule-surfaced sheets, and roof shingles.
Mineral Stabilizer: A fine, water-insoluble inorganic material, used in a mixture with sold or semi-solid bituminous materials.
Mineral Surfaced Roofing: Built-up roofing materials whose top ply consists of a granule-surfaced sheet.
Mineral Surfaced Sheet: A felt that is coated on one or both sides with asphalt and surfaced with mineral granules.
Modified Bitumen: Are composite sheets consisting of copolymer modified bitumen often reinforced and sometimes surfaced with various types of films, foils and mats.
Mole Run: A meandering ridge in a roof membrane not associated with insulation or deck joints.
Mop-and-Flop: An application procedure in which roofing elements (insulation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate locations, are coated with adhesive, and are then turned over and applied to the substrated.
Mopping: The application of hot bitumen with a mop or mechanical applicator to the substrate or to the felts of a built-up roof membrane.
Solid Mopping: A continuous mopping of a surface, leaving no unmopped areas.
Spot Mopping: A mopping pattern in which hot bitumen is applied in roughly circular areas, leaving a grid of unmopped, perpendicular bands on the roof.
Sprinkle Mopping: A random mopping pattern in which heated bitumen beads are strewn onto the substrate with a brush or mop.
Strip Mopping: A mopping pattern in which hot bitumen is applied in parallel bands.
Neoprene: A synthetic rubber (polychloroprene) used in liquid-applied and sheet-applied elastomeric roof membranes or flashings.
Nineteen-Inch Selvage: A prepared roofing sheet with a 17-inch granule surfaced exposure and a nongranulesurfaced 19-inch selvage edge. This material is sometimes referred to as SIS or as Wide Selvage Asphalt Roll Roofing Material Surfaced with Mineral Granules.
Ninety-Pound: A prepared organic felt roll roofing with a granule surfaced exposure that has a mass of approximately 909 pounds per 100 square feet.
Organic: Being or composed of hydrocarbons of their derivatives, or matter of plant or animal origin.
Parapet Wall: That part of any wall entirely above the roof.
Perlite: An aggregate used in lightweight insulating concrete and in preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.
Perm: A unit of water vapor transmission defined as 1 grain of water vapor per square foot per hour per inch of mercury pressure difference (1 inch of mercury = .49 psi). The formula for per is: P=GRAINS OF WATER VAPOR/SQUARE FOOT HOUR INCH MERCURY
Permeance: An index of materialÕs resistance to water vapor transmission. (See Perm)
Phased Application: The installation of a roof system or water proofing system during two or more separate time intervals.
Picture Framing: A rectangular pattern of ridges in a roof membrane over insulation or deck joints.
Pitch: (See Coal Tar and Incline)
Pitch Pocket: A flange, open-bottomed, metal container placed around columns or other roof penetrations that is filled with hot bitumen or flashing cement to seal the joint. The used of pitch pockets is not recommended by NRCA.
Plastic Cement: (See Flashing Cement)
Plastomeric: A plastic like polymer consisting of any of various complex organic compounds produced by polymerization which are capable of being molded, extruded or coast into various shapes or films. Generally they are thermo plastic in nature, i.e., they will soften when heated and harden when cooled.
Ply: A layer of felt in a built-up roof membrane system. A four-ply membrane system has four plies of felt.
Point Weight: (See Felt Mill Ream)
Pond: A roof surface that is incompletely drained.
Positive Drainage: The drainage condition in which consideration has been made for all loading deflections of the deck, and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of rainfall.
Primer: A thin, liquid bitumen applied to a surface to improve the adhesion of subsequent applications of bitumen.
Rake: The slope edge of a roof at the first or last rafter.
Re-covering: The process of covering an existing roofing system with a new roofing system.
Re-entrant Corner: An inside corner of a surface, producing stress concentrations in the roofing or waterproofing membrane.
Reglet: A groove in a wall or other surface adjoining a roof surface for use in the attachment of counterflashing.
Reinforced Membrane: A roofing or waterproofing membrane reinforced with felts, mats, fabrics or chopped fibers.
Relative Humidity: The ratio of the weight of moisture in a given volume of air-vapor mixture to the saturated (maximum) weight of water vapor at the same temperature, expressed as a percentage. For example, if the weight of the moist air is one pound and if the air could hold two pounds of water vapor at a given temperature, the relative humidity (RH) is 50 percent.
Replacement: The practice of removing an existing roof system and replacing it with a new roofing system.
Re-roofing: The process of re-covering or replacing an existing roofing system. (See Re-covering and Replacement)
Ridging: An upward, tenting displacement of a roof membrane frequently occurring over insulation joints, deck joints and base sheet edges.
Roll Roofing: Smooth-surfaced or mineral-surfaced coated felts.
Roof Assembly: An assembly of interacting roof components (including the roof deck) designed to weatherproof and, normally, to insulated a buildingÕs top surface.
Roof Cement: (See Flashing Cement)
Roofer: The trade name for the workman who applied roofing material.
Roof System: A system of interacting roof components (not including the roof deck) designed to weather proof and, normally, to insulate a buildingÕs top surface.
Saddle: A small structure that helps channel surface water to drains, frequently located in a valley, and often constructed like a small hip roof or like a pyramid with a diamond shape base. (See Cricket)
Saturated Felt: A felt that has been partially saturated with low softening point bitumen.
Screen: An apparatus with circular apertures for separating sizes of materials.
Scuttle: A hatch that provides access to the roof from the interior of the building.
Seal: (1) A narrow closure strip made of bituminous materials; (2) to secure a roof from the entry of moisture.
Sealant: A mixture of polymers, fillers, and pigments used to fill and seal joints where moderate movement is expected; it cures to a resilient solid.
Selvage: An edge or edging that differs from the main part of (1) a fabric, or (2) granule-surfaced roll roofing material.
Selvage Joint: A lapped joint designed for mineral-surfaced cap sheets. The mineral surfacing is omitted over a small portion of the longitudinal edge of the sheet below in order to obtain better adhesion of the lapped cap sheet surface with the bituminous adhesive.
Shark Fin: An upward-curled felt side lap or end lap.
Shingle: (1) A small unit of prepared roofing material designed for installation with similar units in overlapping rows in inclines normally exceeding 25 percent; (2) to cover with shingles; (3) to apply any sheet material in overlapping rows like shingles.
Shingling: (1) The procedure of laying parallel felts so that one longitudinal edge of each felt overlaps and the other longitudinal edge underlaps, and adjacent felt. (See Ply) Normally, felts are shingled on a slope so that the water flows over rather than against each lap; (2) The application of shingles to a sloped roof.
Sieve: An apparatus with apertures for separating sizes of material.
Slag: A hard, air-cooled aggregate that is left as a residue from blast furnaces, used as a surfacing aggregate.
Slippage: Relative lateral movement of adjacent components of a built-up membrane. It occurs mainly in roofing membranes on a slope, sometimes exposing the lower plies or even the base sheet to the weather.
Slope: (See Incline)
Smooth-Surfaced Roof: A built-up roof membrane surfaced with a layer of hot-mopped asphalt, cold-applied asphalt clay emulsion, cold-applied, asphalt cutback, or sometimes with an unmopped inorganic felt.
Softening Point: The temperature at which bitumen becomes soft enough to flow, as determined by an arbitrary, closely defined method. (See Dropback)
Softening Point Drift: A change in the softening point of bitumen during storage or application. (See Dropback)
Solid Mopping: (See Mopping)
Special Steep Asphalt: (See Asphalt)
Split: A membrane tear resulting from tensile strength.
Split Sheet: (See Nineteen-Inch Selvage)
Spot Mopping: (See Mopping)
Sprinkle Mopping: (See Mopping)
Spudding: the process of removing the roofing aggregate and most of the bituminous top coating by scraping and chipping.
Square: The term used to describe 100 square feet of roof area.
Stack Vent: A vertical outlet in a built-up roof system designed to relieve the pressure exerted by moisture vapor between the roof membrane and the vapor retarder or deck.
Steep Asphalt: (See Asphalt)
Strip Mopping: (See Mopping)
Stripping or Strip-Flashing: (1) The technique of sealing a joint between metal and the built-up roof membrane with one or two plies of felt or fabric and hot-applied or cold-applied bitumen; (2) the technique of taping joints between insulation boards or deck panels.
Substrate: The surface upon which the roofing or waterproofing membrane is applied (i.e., the structural deck or insulation)
Sump: An intentional depression around a drain.
Superimposed Loads: Loads that are added to existing loads. For example, a large stack of insulation boards placed on top of a structural steel deck.
Tapered Edge Strip: A tapered insulation strip used to (1) elevate the roof at the perimeter and at curbs that extend through a roof; (2) provide a gradual transition from one layer of insulation to another.
Taping: (See Stripping)
Tar: 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.
Tarred Felt: (See Coal-Tar Felt)
Test Cut: A sample of the roof membrane that is cut from a roof membrane to: (a) determine the weight of the average interply bitumen moppings; (b) diagnose the condition of the exiting membrane (e.g., to detect leaks or blisters).
Thermal Conductance (C): A unit of heat flow that is used for specific thicknesses of material or for materials of combination construction, such as laminated insulation.
Thermal Conductivity (k): The heat energy that will be transmitted by conduction through one square foot of one inch this homogeneous material in one hour when there is a difference of one degree Fahrenheit perpendicularly across the two surfaces of the material.
Thermal Insulation: A material applied to reduce the flow of heat.
Thermal Resistance (R): An index of materialÕs resistance to heat flow; it is the reciprocal of thermal conductivity (k) or thermal conductance (C).
Thermal Shock: The stress producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a rain shower follows brilliant sunshine.
Through-Wall Flashing: A water-resistant membrane or material assembly extending through a wall and its cavities, positioned to direct water entering the top of the wall to the exterior.
Tuck Pointing: (1) Troweling mortar into a joint after masonry units are laid;
Underwriters Laboratories (UL): An organization that classifies roof assemblies for their fire characteristics and wind uplift resistance.
Vapor Migration: The movement of water vapor from a region of high vapor pressure to a region of lower vapor pressure.
Vapor Retarder: A material designed to restrict the passage of water through a roof or wall.
Vent: An opening designed to convey water vapor or other gas from inside a building or a building component to the atmosphere, thereby relieving vapor pressure.
Vermiculite: An aggregate used in lightweight insulating concrete, formed by the heating and consequent expansion of a micaceous mineral.
Waterproofing: Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.
Wythe: A masonry wall, one masonry unit, a minimum of two inches thick.
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