Glossary of Roofing Terms
Canopy: any overhanging or projecting roof structure,
typically over entrances or doors. Sometimes the extreme end is unsupported.
Cant: a beveling of foam at a right angle joint for
strength and water run off.
Cant Strip: a beveled or triangular-shaped strip of wood, wood
fiber, perlite, or other material designed to serve
as a gradual transitional plane between the horizontal surface of a roof deck
or rigid insulation and a vertical surface.
Cap Flashing: usually composed of metal, used to cover
or shield the upper edges of the membrane base flashing, wall flashing, or
primary flashing. (See Flashing and Coping.)
Cap Sheet: a granule-surface coated sheet used as the top ply
of some built-up or modified bitumen roof membranes and/or flashing.
Capacitance Meter: a device used to locate moisture or wet
materials within a roof system by measuring the ratio of the change to the
potential difference between two conducting elements separated by a nonconductor.
Capillary Action: the action that causes movement of liquids
by surface tension when in contact with two adjacent surfaces such as panel
side laps.
Caulk: a material (usually a composition of vehicle and
pigment) used for filling/sealing joints or junctures, where no elastomeric properties are required. (See Sealant.)
Caulking: (1) the physical process of sealing a joint or
juncture; (2) sealing and making weather-tight the joints, seams, or voids
between adjacent units by filling with a sealant.
Cavity Wall: a wall built or arranged to provide an air space
within the wall (with or without insulating material), in which the inner and
outer materials are tied together by structural framing.
C-Channel: a structural framing member.
Cementitious Waterproofing: heavy
cement-based compounds and various additives that are mixed and packaged for
use in a dry form; the packaged mixture is then mixed with water and liquid
bonding agents to a workable concrete-like consistency.
Centipoise: a unit of measure of absolute
viscosity. (Note: The viscosity of water is one centipoise.
The lower the number, the less the viscosity.)
Centistoke: a unit of viscosity - the ratio
of a liquid's absolute viscosity to the density of that liquid.
Chalk: a powdery residue on the surface of a material.
Chalk Line: a line made on the roof by snapping a taut string
or cord dusted with colored chalk. Used for alignment purposes.
Chalking: the degradation or migration of an ingredient, in
paints, coatings, or other materials.
Channel Flashing: For steep-slope roof construction) a type
of flashing used at roof-to-wall junctures and other roof-to-vertical plane
intersections where an internal gutter is needed to handle runoff. Commonly
used with profile tile.
Chemical Resistance: the ability to withstand
contact with specified chemicals without a significant change in properties.
Chimney: stone, masonry, prefabricated metal, or a wood
framed structure, containing one or more flues, projecting through and above
the roof.
Chlorinated Polyethylene (CPE): a thermoplastic
material, used for single-ply roof membranes, composed of high molecular weight
polyethylene which has been chlorinated - a process that yields a flexible
rubber-like material.
Chlorosulfonated Polyethylene (CSPE or CSM): (probably
best known by the DuPont trade name Hypalon™) a
synthetic, rubber-like thermoses material, based on high molecular weight
polyethylene with suphonyl chloride, usually
formulated to produce a self-vulcanizing membrane. Classified by ASTM Standard
D 501 9-89.
Cladding: a material used as the exterior wall enclosure of
a building.
Cleat: a metal strip, plate or metal angle piece,
either continuous or individual ("clip"), used to secure two or more
components together.
Clerestory: an upward extension of enclosed space created by
carrying a setback vertical, wall (typically glazed) up and through the roof
slope. Two intersecting shed roofs on different planes. (See Figure 1.)
Clip: an individual (discrete) cleat. (See Cleat.)
Clipped
Glable: a gable cutback at the peak in
a hip-roof form. (See Figure 2.)
Closure Strip: a metal or resilient strip, such as
neoprene foam, used to close openings created by joining metal panels or sheets
and flashings.
Coal Tar: a dark brown to black colored, semi-solid hydrocarbon
obtained as residue from the partial evaporation or distillation of coal tars.
Coal tar pitch is further refined to conform to the following roofing grade
specifications:
» Coal Tar Bitumen: a
proprietary trade name for Type lil coal tar used as
the dampproofing or waterproofing agent in dead-level
or low-slope built-up roof membranes, conforming to ASTM D 450, Type lilt
» Coal Tar Pitch: a coal
tar used as the waterproofing agent in dead-level or low-slope built-up roof
membranes, conforming to ASTM Specification D 450, Type I or Type lilt
»
Coal
Tar Waterproofing Pitch: a coal tar used as the dampproofing
or waterproofing agent in belowgrade structures,
conforming to ASTM Specification D 450, Type II.
Coal Tar Felt: a felt that has been saturated with
refined coal tar.
Coal Tar Roof Cement: a trowelable
mixture of processed coal tar base, solvents, mineral fillers and/or fibers.
Classified by ASTM Standard D 4022 Coal Tar Roof Cement.
Coated Fabric: fabrics that have been impregnated and/or
coated with a plastic-like material in the form of a solution, dispersion
hot-melt, or powder. The term also applies to materials resulting from the
application of a preformed film to a fabric by means of calendering.
Coated Felt (Sheet): (1) an asphalt-saturated felt
that has also been coated on both sides with harder, more viscous
"coating" asphalt; (2) a glass fiber felt that has been
simultaneously impregnated and coated with asphalt on both sides.
Coating: a layer of material spread over a surface for
protection or decoration. Coatings for SPF are generally liquids, semi-liquids,
or mastics; spray, roller, or brush applied; and cured to an elastomeric consistency.
Coefficient of Thermal Expansion: a mathematical
formulation used to predict the change in dimension (typically length) of a
material as a function of temperature change.
Cohesion: the degree of internal bonding of one substance to
itself.
Cold Forming: the process of using press brakes, roll
farmers, etc., to shape metal into desired profiles at ambient room
temperature.
Cold Process Built-Up Roof: a continuous, semi-flexible
roof membrane, consisting of a ply or plies of felts, mats or other
reinforcement fabrics that are laminated together with alternate layers of
liquid-applied (usually asphalt-solvent based) roof cements or adhesives
installed at ambient or a slightly elevated temperature.
Cold Rolled: the process of forming steel into sheets, panels,
or shapes on a series of rollers at ambient room temperatures.
Collector Box: see Conductor Head.
Color Stability: the ability of a material to retain its
original color.
Column: a primary structural member used in a vertical
position in a building to transfer loads from horizontal structural members
(e.g., main roof beams, trusses, or rafters) to the foundation/footing.
Combing Ridge: a term used to describe an installation of
finishing slate at the ridge of a roof whereby the slates on one side project
beyond to the apex of the ridge.
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.
Composition Shingle: a unit of asphalt shingle
roofing.
Compounded Thermoplastics: a category of roofing
membranes made by blending thermoplastic resins with plasticizers, various
modifiers, stabilizers, flame retardants, UV absorbers, fungicides, and other
proprietary substances, alloyed with proprietary organic polymers. Some of the
membranes listed in this generic category are CPA, EIP, NBP, and TPA.
Compressive Strength: the ability of materials and
components to resist deformation or other damage caused by the weight of
compression of either live or dead loads.
Concealed-Nail Method: a method of asphalt roll
roofing application in which all nails are driven into the underlying course of
roofing and covered by an adhered, overlapping course.
Condensate: the liquid resulting from the condensation of a
gas or vapor.
Condensation: the conversion of water vapor or other gas
to liquid state as the temperature drops or atmospheric pressure rises. (Also
see Dew Point.)
Conductance, Thermal: the thermal transmission in
unit time through unit area of a particular body or assembly having defined
surfaces, when unit average temperature difference is established between the
surfaces. C=Btu/h~ft2~°F.
Conductor Head: a transition component between a
through-wall scupper and downspout to collect and direct run-off water.
Contact Cements: adhesives used to adhere or bond various
roofing components. These adhesives adhere mated components immediately on
contact of surfaces to which the adhesive has been applied.
Contamination: the process of making a material or
surface unclean or unsuited for its intended purpose, usually by the addition
or attachment of undesirable foreign substances.
Coping: the covering piece on top of a wall which is
exposed to the weather, usually made of metal, masonry, or stone. It is
preferably sloped to shed water back onto the roof.
Copolymer: the product of polymerization of two or more
substances at the same time; a "mixed" polymer.
Copolymerization: a chemical reaction that results in the
bonding of two or more dissimilar monomers to produce large, long-chain
molecules which are copolymers.
Copper: a natural weathering metal used in metal roofing;
typically used in 16 or 20 ounce per square foot thickness (4.87 or 6.10 kg/sq
m).
Cornice: the decorative horizontal molding or projected
roof overhang.
Counter Batten: vertical wood strips installed on sloped
roofs over which horizontal battens are secured. The primary roof covering is
attached or secured to these horizontal battens.
Counterflashing: formed metal sheeting secured
on or into a wall, curb, pipe, rooftop unit, or other surface, to cover and
protect the upper edge of the membrane base flashing or underlying metal
flashing and associated fasteners from exposure to the weather.
Course: (1) the term used for each row of shingles of
roofing material that forms the roofing, waterproofing, or flashing system; (2)
one layer of a series of materials applied to a surface (e.g., a five-course
wall flashing is composed of three applications of roof cement with one ply of
felt or fabric sandwiched between each layer of roof cement.)
Cove: see Fillet.
Cover Plate: a metal strip sometimes installed over the joint
between formed metal pieces.
Coverage: the surface area covered by a specific quantity of
a particular material.
CPE: Chlorinated Polyethylene.
Crack: a non-linear separation or fracture occurring in
a material. May be generally caused by induced stress, dimensional instability,
or substrate movement. Some cracks may be more of a linear separation or
fracture. (See
Creep: the permanent deformation of a roofing material
or roof system caused by movement of the roof membrane, or compression of a
roof insulation board at fastener positions, that results from continuous load
or thermal stress or loading. Creep at roof temperature is sometimes called
"cold flow."
Cricket: an elevated roof substrate or structure,
constructed to divert water around a chimney, curb, away from a wall, expansion
joint, or other projection/penetration. (See Saddle.)
Cross Ventilation: the effect that is provided when air moves
through a roof cavity between the vents.
CSPE: chlorosulfonated
polyethylene.
Cupola: a relatively small roofed structure, generally set
on the ridge or peak of a main roof area. (See Figure 3.)
Curb: (1) a raised member used to support roof
penetrations, such as skylights, mechanical equipment, hatches, etc. above the
level of the roof surface; (2) a raised roof perimeter relatively low in
height.
Cure: a process whereby a material is caused to form
permanent molecular linkages by exposure to chemicals, heat, pressure, and/or
weathering.
Cure Time: the time required to effect curing. The time
required for a material to reach its desirable long-term physical
characteristics.
Cured Concrete: concrete that has attained its intended
design performance properties.
Curing Agent: an additive in a coating or adhesive that
results in increased chemical activity between the components with an increase
or decrease in rate of cure.
Curing Compound: a liquid that is sprayed or otherwise
applied to newly placed concrete which retards the loss of water during curing.
Cutback: solvent-thinned bitumen used in cold-applied
("process") roofing adhesives, roof cements, and roof coatings.
Cutoff: a permanent detail designed to seal and prevent
lateral water movement in an insulation system, and used to isolate sections of
a roofing system. (Note: A cutoff is different from a tie-off, which may be a
temporary or permanent seal.) (See Tie-Off.)
Cutout: the open portions of a strip shingle between the
tabs. (See Figure 4.)
Dampproofing: treatment of a surface or structure to resist the
passage of water in the absence of hydrostatic pressure.
Dead Level: essentially horizontal or flat, as
in a roof deck or rooftop with no intentional slope to the roof drains. Also
referred to as zero (0) slope. (See Slope.)
Dead-Level Asphalt: see Asphalt.
Dead Loads: permanent non-moving loads that
result from the weight of a building's structural and architectural components,
mechanical and electrical equipment, and the roof assembly itself. Essentially
the same as "dead weight" or "dead weight loads."
Deck: a structural component of the
roof of a building. The deck must be capable of safely supporting the design
dead and live loads, including the weight of the roof systems, and the
additional live loads required by the governing building codes. Decks are
either non-combustible (e.g., corrugated metal, concrete, or gypsum) or
combustible (e.g., wood plank or plywood), and provide the substrate to which
the roofing or waterproofing system is applied.
Deflection (Bowing, Sagging): the downward displacement of a
structural member or system under load.
Degradation: a deleterious change in the
chemical structure, physical properties, or appearance of a material due to
natural or artificial exposure (e.g., exposure to radiation, moisture, heat,
freezing, wind, ozone, oxygen, etc.).
Degree Days: the difference between a reference
temperature (usually 65°F [1 8.3°C]) and the mean temperature for the day,
times 24 hours, times the number of days in the period. Degree days are used to
compare the severity of cold or heat during the heating or cooling season.
Delamination: separation
of the laminated layers of a component or system.
Design Loads: those loads specified in building
codes or standards published by federal, state, county, or city agencies, or in
owners' specifications to be used in the design of a building.
Dew Point Temperature: the temperature at which water
vapor condenses in cooling air at the existing atmospheric pressure and vapor
content. Cooling at or below the dew point will cause condensation.
Diaphragm: see Roof Diaphragm.
Diffusion: the movement of water vapor from
regions of high concentration (high water vapor pressure) toward regions of
lower
Dimensional Shingle: a shingle that is textured, overlayed, or laminated and designed to produce a
three-dimensional effect. (Also see Laminated Shingles and Architectural
Shingles).
Dimensional Stability: the ability of a material to
resist change in length, width, and/or thickness that results from exposure to
elevated or freezing temperatures, and moisture, over time.
Dome: a roof that is shaped like a
half-circle, or a variation of one.
Domer: a framed projection through the
slopping plane of a roof. (See figure 5)
Double Coverage: application of asphalt, slate, or
wood roofing such that the lapped portion is at least 2 inches (51mm) wider
than the exposed portion, resulting in two layers of roofing material over the
deck.
Double Graveling: the process of applying two layers
or flood coats of bitumen and aggregate to a built-up roof. Loose aggregate
should be swept from the first application prior to the second coating of
bitumen and aggregate. Approximately 50% of the second aggregate application
will remain adhered in the bitumen flood coat unless physically removed.
Double Lock Standing Seam: a standing seam that utilizes a
double, overlapping interlock between two seam panels. (See Standing Seam.)
Downspout: a conduit used to carry runoff
water from a scupper, conductor head, or gutter of a building to a lower roof
level, or to the ground or storm water runoff system.
Drain: an outlet or other device used to
collect and direct the flow of runoff water from a roof area.
Drip Edge: a metal flashing, or other overchanging component, with an outward projecting lower
edge, intended to control the direction of dripping water and help protect
underlying building components. A drip edge also can be used to break the
continuity of contact between the roof perimeter and wall components to help
prevent capillary action.
Dry: (1) to change the physical state
of a material by the loss of components through evaporation, absorption,
oxidation, or a combination of these effects; (2) the absence of water or
moisture.
Dry Film Thickness: the thickness, expressed in mils,
of an applied and cured coating or mastic. For comparison, see Wet Film
Thickness.
Dry-In or Dry-In Felt: usually the underlayment
or the process of applying the underlayment for steep
roofing.
Drying Time: the time required for the loss of
volatile components so that the material will no longer be adversely affected
by weather conditions such as dew, rain, or freezing.
Dual Level Drain: in waterproofing, an outlet or
other device with provisions for drainage at both the wearing surface level and
the waterproofing membrane level used to collect and direct the flow of runoff
water from a horizontal slip. (See NRCA Waterproofing Detail WP-9.)
Durability: the ability to withstand physical,
chemical, or environmental abuse.
Dust Free: a surface is considered dust free
when a finger can be lightly run over the surface without picking up any dirt,
dust, or chalk on the finger.
Dynamic Load: any load which is nonstatic, such as a wind load or a moving live load.
Eave: a
projecting edge of a roof that extends beyond the supporting wall. (See Figure
6.)
Eave
Height: the vertical dimension from finished grade to the
cave.
Eaves-Trough: see
Gutter.
Edge Stripping: membrane flashing strips cut to specific
widths used to seal/flash perimeter edge metal and the roof membrane.
Edge Venting: the practice of providing regularly spaced
or continuously protected (e.g., louvered) openings along a roof edge or
perimeter, used as part of a ventilation system to dissipate heat and moisture
vapor.
Efflorescence: the formulation of crystalline deposits,
generally whitish in color, on the surface of stone, brick, concrete, or other
masonry surface when moisture moves through and evaporates on the masonry. May
also be caused by free alkalies leached from mortar,
grout, or adjacent concrete.
Elasticity: the property of matter by virtue of which it tends
to return to its original size and shape after removal of a stress or force
which caused a deformation.
Elastomer: natural or synthetic material
which, at room temperature, can be stretched under low stress and, upon
immediate release of the stress or force, will return quickly to its
approximate original dimensions.
Elastomeric: the elastic, rubber-like
properties of a material that will stretch when pulled and will return
relatively quickly to its original shape when released.
Elastomeric Coating: a
coating system which, when fully cured, is capable of being stretched at least
twice its original length (100% elongation) and recovering to its original
dimensions.
Electrolyte: a liquid, most often a solution, that will conduct
current.
Elongation: the ability of a material (e.g., roofing membrane)
to be stretched by the application of a force.
Embedment: (1) the process of installing or pressing-in a
reinforcement felt, fabric, mat or panel uniformly into bitumen or adhesive;
(2) the process of pressing granules into coating during the manufacture of
factory-prepared roofing; (3) the process whereby ply sheet, aggregate, or
other roofing components settle into hot- or cold-applied bitumen via the force
of gravity.
Embrittlement: the loss of flexibility or
elasticity of a material. The transition of a flexible material to a brittle
state.
Emulsion: a dispersion of fine particles or globules in a
liquid. (See Asphalt Emulsion and Bitumen Emulsion.)
End Lap: the distance of overlap where one ply, panel, or
piece extends beyond the end of the immediately adjacent underlying ply, panel,
or piece. (See Figure 7. )
Envelope (Bitumen-Stop): a continuous edge seal formed
at the perimeter and at penetrations by extending the base sheet or one ply of
felt beyond the edge of the membrane field plies. After all overlying field
plies or insulation are in place, the extended ply is turned back onto the
membrane and adhered. The envelope is intended to prevent bitumen seepage from
the edge of the membrane.
EPDM: Ethylene Propylene Diene
Monomer (See also Ethylene Propylene Diene Terpolymer.)
Epichlorohydrin (ECH): a synthetic rubber
including two epichlorohydrin based elastomers. It is similar to and compatible with EPDM. ECH
is typically used in lieu of EPDM when enhanced resistance to animal fat or
other oils is needed.
Epoxy: a class of synthetic, thermosetting resins that
produce tough, hard, chemical-resistant coatings and adhesives.
Equiviscous Temperature (EVT): the
temperature at which a bitumen attains the proper viscosity for built-up
membrane application.
Equiviscous Temperature (EVT)
Equiviscous Temperature (EVT) for Asphalt: the
recommended EVT for roofing asphalt (ASTM D312, Type I, 11, 111, or IV) is as
follows:
» Mop
Application: the temperature at which the asphalt's apparent viscosity is 125 centipoise (0.125 Pass).
»
Mechanical Spreader Application: the temperature
at which the asphalt's apparent viscosity is 75 centipoise
(0.075 Pans).
Note: If there are simultaneous mop and mechanical spreader applications, in order to
avoid the use of two kettles, the EVE for mechanical spreader application may
be used for both application techniques.
Equiviscous Temperature (EVA) for Coal Tar: the
recommended EVT for roofing coal tar (ASTM D 450, Type I or lil)
is the temperature at which the coal tar's apparent viscosity is 25 centipoise (0.025 Pans).
Ethylene Interpolymers (EIP):
a group of thermoplastic compounds generally based on PVC polymers from which
certain single-ply roofing membranes can be formulated.
Ethylene Propylene Diene Terpolymer
(EPDM): designated nomenclature of ASTM for a terpolymer of ethylene, propylene, and a diene. EPDM material is a thermosetting synthetic elastomer.
EVT: Equiviscous
Temperature
Exhaust Ventilation: air that is typically vented
or exhausted from the roof cavity, typically through vents installed on the
upslope portion of the roof. For example, with most steep-slope roof assemblies
exhaust vents are typically located at or near the ridge.
Expansion Cleat: a cleat designed to handle thermal
movement of the metal roof panels.
Expansion Joint: a structural separation between two
building elements that allows free movement between the elements without damage
to the roofing or waterproofing system.
Exposed-Nail Method: a method of asphalt roll roofing
application in which all nails are driven into the adhered, overlapping course
of roofing. Nails are exposed to the weather.
Exposure: (1) the traverse dimension of a roofing element or
component not overlapped by an adjacent element or component in a roof
covering. For example, the exposure of any ply in a built-up roof membrane may
be computed by dividing the felt width minus 2 inches (51 mm) by the number of
shingled plies; thus, the exposure of 36 inch (91 4mm) wide felt in a shingled,
four-ply membrane should be approximately 84/~ inches (21 6mm) (See Figure 8);
(2) the dimension of sidewall or roofing covering that is not covered or
overlapped by the upslope course of component. The typical exposure for a
standard-size, 3-tab shingle is 5 inches (127mm), depending upon manufacturer
specifications. (See Figure 9.)
Extrusion: a manufacturing process which consists of forcing
batched and formulated material (which may be molten) through an orifice called
a "die." The shape and dimensions of the orifice determine the shape
and dimensions of the finished product. Extrusion is one method by which some
single-ply roofing membranes are manufactured.
Eyebrow: a dormer, usually of small size, whose roof line
over the upright face is typically an arched curve, turning into a reverse
curve to meet the horizontal at either end. Also, a small shed roof projecting
from the gable end of the larger, main roof area.
