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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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| -F- |
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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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| -H- |
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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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| -K- |
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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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| -M- |
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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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| -N- |
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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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| -Q-R- |
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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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| -U- |
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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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| -V- |
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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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| -W-X-Y-Z- |
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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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