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Aggregrate: (1) crushed stone, crushed slag or water worn
gravel used for surfacing a built-up roof; (2) any granular mineral material.
Alligatoring: the cracking
of the surfacing bitumen on a built-up roof, producing a pattern of cracks
similar to an alligator's hide; the cracks may or may not extend through
the surfacing bitumen.
Application Rate: the quantity (mass,
volume or thickness) of material applied per unit area.
Area Divider: a raised, double wood
member attached to a properly flashed wood base plate that is anchored
to the roof deck. It is used to relieve thermal stresses in a roof system
where no expansion joints have been provided.
Asbestos: a group of natural, fibrous,
impure silicate materials.
Asphalt: a dark brown to black cementitious
material in which the predominating constituents are bitumens, which occur
in nature or are obtained in petroleum processing.
Asphalt, Air Blown: an asphalt produced
by blowing air through molten asphalt at an elevated temperature to raise
its softening point and modify other properties.
Asphalt Felt: an asphalt-saturated
felt or an asphalt-coated felt.
Asphalt Mastic: a mixture of asphaltic
material and graded mineral aggregate that can be poured when heated but
requires mechanical manipulation to apply when cold.
Asphalt, Steam Blown: an asphalt produced
by blowing steam through molten asphalt to modify its properties.
Asphaltene: a high molecular weight
hydrocarbon fraction precipitated from asphalt by a designated paraffinic
naphthasolvent at a specified temperature and solvent-asphalt ratio.
Asphaltic Roof Fill: a blend of asphalt
and pearlite aggregate typically installed at precise drainage slopes.
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Backnailing: the practice of blind-nailing
roofing felts to a substrate in addition to hot-mopping to prevent slippage.
Base Ply: the lowermost ply of roofing
material in a roof membrane assembly.
Base Sheet: a saturated or coated felt
placed as the first ply in some multi-ply built-up roof membrane.
Bitumen: (1) a class of amorphous,
black or dark colored, (solid, semi-solid or viscous) cementitious substances,
natural or manufactured, composed principally of high molecular weight
hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars,
pitches and asphaltites; (2) a generic term used to denote any material
composed principally of bitumen.
Bituminous: containing or treated with
bitumen. Examples: bituminous concrete, bituminous felts and fabrics,
bituminous pavement.
Bituminous Emulsion: (1) a suspension
of minute globules of bituminous material in water or in an aqueous solution;
(2) a suspension of minute globules of water or an aqueous solution in
a liquid bituminous material (invert emulsion).
Bituminous Grout: a mixture of bituminous
material and fine sand that will flow into place without mechanical manipulation
when heated.
Blackberry: a small bubble or blister
in the flood coating of a gravel-surfaced roof membrane.
Blind Nailing: the practice of nailing
the back portion of a roofing ply in a manner that the fasteners are not
exposed to the weather in the finished product.
Blister: an enclosed pocket of air
mixed with water or solvent vapor, trapped between impermeable layers
of felt, or between the felt and substrate.
Blocking: wood built into a roofing
system above the deck and below the membrane and flashing to stiffen the
deck around an opening, act as a stop for insulation, or to serve as a
nailer for attachment of the membrane or flashing.
Bond: the adhesive and cohesive forces
holding two roofing components in intimate contact.
Brooming: embedding a ply of roofing
material by using a broom to smooth out the ply and ensure contact with
the adhesive under the ply.
British Thermal Unit (BTU): the heat
energy required to raise the temperature of 1 pound of water 1 degree
Fahrenheit.
Built-Up Roof Membrane: a continuous,
semi-flexible roof membrane assembly, consisting of plies of saturated
felts, coated felts, fabrics or mats between which alternate layers of
bitumen are applied, generally surface with mineral aggregate, bituminous
materials, or a granule-surfaced roofing sheet.
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Cant Strip: a beveled strip used under
flashing to modify the angle at the point where the roofing or waterproofing
membrane meets any vertical element.
Capillarity: the action by which the
surface of a liquid (where it is in contact with a solid) is elevated
or depressed, depending upon the relative attraction of the molecules
of the liquid for each other and for those of the solid.
Cap Sheet: a granule-surfaced coated
sheet used as the top ply of a built-up roof membrane or flashing.
Caulking: a composition of vehicle
and pigment, used at ambient temperatures for filling joints, that remains
plastic for an extended time after application.
Coal Tar: a dark brown to black, semi-solid
hydrocarbon obtained as residue from the partial evaporation or distillation
of coal tar.
Coal-Tar Felts: a felt that has been
saturated with refined coal tar.
Coated Sheet Felts: (1) an asphalt
felt that has been coated on both sides with harder, more viscous asphalt;
(2) a glass fiber felt that has been simultaneously impregnated and coated
with asphalt on both sides.
Cold-Processing Roofing: a continuous,
semi-flexible roof membrane, consisting of plies of felts, mats or fabrics
that are laminated on a roof with alternate layers of cold-applied roof
cement and surfaced with a cold-applied coating.
Condensation: the conversion of water
vapor or other gas to liquid as the temperature drops or the atmospheric
pressure rises.
Coping: the covering piece on top of
a wall exposed to the weather, usually sloped to shed water.
Counterflashing: formed metal or elastomeric
sheeting secured on or into a wall, curb, pipe, rooftop unit or other
surface, to cover and protect the upper edge of a base flashing and its
associated fasteners.
Course: (1) the term used for each
application of material that forms the waterproofing system or the flashing;
(2) one layer of a series of materials applied to a surface (i.e., a five-course
wall flashing is composed of three applications of mastic with one ply
of felt sandwiched between each layer of mastic).
Coverage: the surface area continuously
covered by a specific quantity of a particular roofing material.
Crack: a separation or fracture occurring
in a roof membrane or roof deck, generally caused by thermal induced stress
or substrate movement.
Creep: the permanent deformation of
a roofing material or roof system caused by the movement of the roof membrane
that results from continuous thermal stress or loading.
Cricket: a relatively small, elevated
area of a roof constructed to divert water around a chimney, curb or other
projection.
Cutback: solvent-thinned bitumen used
in cold process roofing adhesives, flashing cements and roof coatings.
Cutoff: a detail designed to prevent
lateral water movement into the insulation where the membrane terminates
at the end of a day's work, or used to isolate sections of the roofing
system. It is usually removed before the continuation of the work.
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Dampproofing: treatment of a surface
or structure to resist the passage of water in the absence of hydorstatic
pressure.
Dead Level: absolutely horizontal,
or zero slope.
Dead Loads: non-moving rooftop loads,
such as mechanical equipment, air conditioning units, and the roof deck
itself.
Deck: the structural surface to which
the roofing or waterproofing system is applied.
Delamination: separation of the plies
in a roof membrane system or separation of laminated layers of insulation.
Dew Point: the temperature at which
water vapor starts to condense in cooling air at the existing atmospheric
pressure and vapor content.
Double-Pour: the process of applying
two layers of aggregate and bitumen to a built-up roof.
Drain: a device that allows for the
flow of water from a roof area.
Dropback: a reduction in the softening
point of bitumen that occurs when bitumen is heated in the absence of
air.
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Edge Sheets: felt strips that are cut
to widths narrower than the standard width of the full felt roll, used
to start the felt shingling pattern at a roof edge.
Edge Stripping: application of felt
strips cut to narrower widths than the normal felt roll width to cover
a joint between flashing and built-up roofing.
Edge Venting: the practice of providing
regularly spaced protected openings along a roof perimeter to relieve
moisture vapor pressure.
Elastomer: a macromolecular material
that returns rapidly to its approximate initial dimensions and shape after
substantial deformation by a weak stress and the subsequent release of
that stress.
Elastomeric: a rubber like synthetic
polymer that will stretch when pulled and will return quickly to its original
shape when released.
Embedment: (1) the process of pressing
a felt, aggregate, fabric, mat, or panel uniformly and completely into
hot bitumen or adhesive; (2) the process of pressing granules into coating
in the manufacture of factory prepared roofing.
Emulsion: the intimate dispersion of
an organic material and water achieved by using a chemical or clay emulsifying
agent.
Envelope: a continuous membrane edge
seal formed at the perimeter and at penetrations by folding the base sheet
or ply over the plies above and securing it to the top of the membrane.
The envelope prevents bitumen seepage from the edge of the membrane.
Equilibrium Moisture: (1) the moisture
content of a material stabilized at a given temperature and relative humidity,
expressed as percent moisture by weight; (2) the typical moisture content
of a material in any given geographical area.
Equiviscous Temperature (EVT): the
temperature at which the viscosity is 75 centipoise for asphalt and 25
centipoise for coal tar products; the recommended temperature plus or
minus 25º F at the time of application.
Expansion Joint: a structural separation
between two building elements that allows free movement between the elements
without damage to the roofing or waterproofing system.
Exposure: (1) the traverse dimension
of a roofing element not overlapped by an adjacent element in any roof
system. The exposure of any ply in a membrane may be computed by dividing
the felt width minus 2 inches by the number of shingled plies; thus, the
exposure of 36 inch-wide felt in a shingled, four-ply membrane should
be 8 1/2 inches; (2) the time during which a portion of a roofing element
is exposed to the weather.
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Fabric: a woven cloth of organic or
inorganic filaments, threads or yarns.
Factory Mutual (FM): an organization
that classifies roof assemblies for their fire characteristics and wind
uplift resistance for insurance companies in the United States.
Factory Square: 108 square feet of
roofing material.
Felt: a flexible sheet manufactured
by the interlocking of fibers through a combination of mechanical work,
moisture and heat. Felts are manufactured principally from vegetable fibers
(organic felts), asbestos fibers (asbestos felts) or glass fibers (glass
fiber felts); other fibers may be present in each type.
Felt Layer: a machine used for applying
bitumen and built-up roofing felts.
Felt Mill Ream: the mass in pounds
of 480 square feet of dry, unsaturated felt; also termed "point weight".
Fine Mineral Surfacing: water-insoluble,
inorganic material, more than 50 percent of which passes the no. 35 sieve,
used on the surface of roofing.
Fishmouth: (1) a half-cylindrical or
half-conical opening formed by an edge wrinkle; (2) in shingles, a half-conical
opening formed at a cut edge.
Flashing: the system used to seal membrane
edges at walls, expansion joints, drains, gravel stops, and other places
where the membrane is interrupted or terminated. Base flashing covers
the edge of the membrane. Cap flashing or counterflashing shields the
upper edges of the base flashing.
Flashing cement: a trowelable mixture
of cutback bitumen and mineral stabilizers, including asbestos or other
inorganic fibers.
Flood Coat: the top layer of bitumen
into which the aggregate is embedded on an aggregate-surfaced built up
roof.
Fluid Applied: an elastomeric material,
fluid at ambient temperature, that dries or cures after application to
form a continuous membrane. Such systems normally do not incorporate reinforcement.
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Glass Felt: glass fibers bonded into
a sheet with resin and suitable for impregnation in the manufacture of
bituminous waterproofing materials, roof membranes, and shingles.
Glass Mat: a thin mat composed of glass
fibers with or without a binder.
Glaze Coat: (1) the top layer of asphalt
in a smooth surfaced built-up roof assembly; (2) a thin protective coating
of bitumen applied to the lower plies or top ply of a built-up roof membrane
when application of additional felts or the flood coat and aggregate surfacing
are delayed.
Gravel: course, granular aggregate,
with pieces larger than sand grains, resulting from the natural erosion
of rock.
Gravel Spot: a flanged device, frequently
metallic, designed to provide a continuous finished edge for roofing material
and to prevent loose aggregate from washing off of the roof.
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Headlap: the minimum distance, measured
at 90 degrees to the eaves along the face of a shingle or felt, from the
upper edge of the shingle or felt to the nearest exposed surface.
Holiday: an area where a liquid-applied
material is missing.
"Hot Stuff" or "Hot": the
roofer's term for hot bitumen.
Hygroscopic: attracting, absorbing
and retaining atmospheric moisture.
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| -I- |
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Ice Dam: a mass of ice formed at the
transition from a warm to a cold roof surface, frequently formed by refreezing
melt-water at the overhang of a steep roof, causing ice and water to back
up under roofing materials.
Incline: the slope of a roof expressed
either in percent or in the number of vertical units of rise per horizontal
unit of run.
Inorganic: being or composed of matter
other than hydrocarbons and their derivatives, or matter that is not of
plant or animal origin.
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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
taken by the number of measurements taken. The results would describe
the job-average for the quantity or dimension. It's generally not considered
a good idea to evaluate roofs on this basis as sample size is small relative
to job size. The NCRA recommends competent visual examination.
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Knot: an imperfection or non-homogeneity
in materials used in fabric construction, the presence of which causes
surface irregularities.
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| -L- |
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Live Loads: moving roof installation
equipment, wind, snow, ice or rain.
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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: 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 roofing shingles.
Mineral Stabilizer: a fine, water-insoluble
inorganic material, used in a mixture with solid 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 a 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
substrate.
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.
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NRCA: National Roofing Contractor Association.
Professional trade group for the roofing industry.
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 nongranule-surfaced
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
90 pounds per 100 square feet.
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Organic: being or composed of hydrocarbons
or their derivatives, or matter of plant or animal origin.
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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 = 0.49 psi).
Permeance: an index of a material's
resistance to water vapor transmission.
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 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 use
of pitch pockets is not recommended by NRCA.
Plastomeric: a plastic-like polymer
consisting of any of various complex organic compounds produced by polymerization
which are capable of being molded, extruded or cast 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.
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.
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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 1 pound and
if the air could hold 2 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.
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 insulate a building's top surface.
Roofer: the trade name for the workman
who applies roofing material.
Roof System: a system of interacting
roof components (not including the roof deck) designed to weather proof
and, normally, to insulate a building's top surface.
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Saddle: a small structure that helps
channel surface water to drains, frequently located in a valley, and often
contracted like a small hip roof or like a pyramid with a diamond shape
base.
Saturated Felt: a felt that has been
partially saturated with low softening point bitumen.
Screen: an apparatus with circular
apertures from 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 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 on 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, the adjacent felt. 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 lies or even the base
sheet to the weather.
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.
Softening Point Drift: a change in
the softening point of bitumen during storage or application.
Solid Mopping: a continuous mopping
of a surface, leaving no unmopped areas.
Split: a membrane tear resulting from
tensile strength.
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.
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.
Strip Mopping: a mopping pattern in
which hot bitumen is applied in parallel bands.
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.
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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.
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.
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 thick 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
a material's 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; (2) final treatment of joints
in cut stonework. Mortar or a putty-like filler is forced into the joint
after the stone is set.
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Underwriters Laboratories (UL): an
organization that classifies roof assemblies for their fire characteristics
and wind uplift resistance.
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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 vapor through a roof or wall.
Vent: an opening designed to convey
water vapor or other gases 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.
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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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