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Terminology Adhered:
When a roof component is glued, bonded or sealed. Ambient Temperature:
Temperature of air - - air temperature. 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. Atactic Polypropylene:
A group of high molecular weight polymers formed by the polymerization
of propylene. Ballast:
Heavy materials used to hold a roof membrane in place. Ballast:
An anchoring material, such as aggregate, precast pavers, which employ
the force of gravity to hold (or assist in holding) membranes in place. Base Flashing:
Strips of roof membrane installed in the vertical flashing area. Blister:
A spongy raised portion of a roof membrane, ranging in area from 1 inch
in diameter and of barely detectable height upward. Blisters result from
the pressure buildup of gases entrapped in the membrane system. These
gases most commonly are air and/or water vapor. Blisters usually involve
delamination of the underlying membrane plies. Bond:
The adhesive and cohesive forces holding two roofing components in
intimate contact. Bonded:
Glued or adhered. Boot:
Covering of flexible material, which may be preformed to a particular
shape, used to seal around a penetration. 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. BTU:
(British Thermal Unit) - The heat energy required to raise the
temperature of 1 pound of water 1 degree Fahrenheit. Buckle:
An upward, elongated tenting displacement of a roof membrane frequently
occurring over insulation or deck joints. A buckle may be an indication
of movement within a roof assembly, and usually associated with improper
installation. Butyl:
A rubber like material produced by copolymerizing isobutylene with a
small amount of isoprene, Butyl may be manufactured in sheets, or
blended with other elastomeric materials to make sealants and adhesives. Cant:
A triangular strip that creates a good angle for flashings. Cant Strip:
A beveled strip of wood or wood fiber that fits into the angle formed by
the intersection of a horizontal surface and a vertical surface. The
45-degree slope of the exposed surface of the cant strip provides a
gradual angular transition from the horizontal surface to the vertical
surface. Capillary:
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. Caulking:
A composition of vehicle and pigment, used at ambient temperatures for
filling joints, that remains plastic for an extended time after
application. Commercial Building:
Public and industrial buildings. These buildings usually have low-slope
roof systems. Condensation:
The conversion of water vapor or other gas to liquid as the temperature
drops or the atmospheric pressure rises. (See Dew-Point) Coping:
The covering piece placed on top of a wall that is exposed to the
weather. It is usually sloped to shed water. Counter flashing:
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. Counter flashing:
The metal flashing that shields the top edges and joints of the base
flashing. Crack:
A separation or fracture occurring in a roof membrane or roof deck
generally caused by thermally induced stress or substrate movement. Creep:
The permanent deformation of a roofing material of roof system caused by
the movement of the roof membrane that results from continuous thermal
stress or loading. Cricket:
A superimposed construction placed in a roof area to assist drainage.
Crickets and Saddles:
Raised areas built into a roof system. They help water flow to drains. Curb:
A raised member used to support roof penetrations, such as skylights,
mechanical equipment, hatches, etc. above the level of the roof surface. Cutoff:
A material seal that is designed to prevent lateral water movement into
the edge of a roof system where the membrane terminate at the end of
day's work or used to isolate section of the roof system. Cutoffs are
usually removed before the continuation of work. Damp proofing:
Treatment of a surface or structure to resist the passage of water in
the absence of hydrostatic pressure. Dead Level:
The term used to describe an absolutely horizontal roof. Zero slope.
(See 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
(including insulation) is applied. Degradation:
A deleterious change in the chemical structure, physical properties, or
appearance of a material due to natural or artificial exposure. 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. Drain:
A device that allows for the flow of water from a roof area. Drainage:
A system that allows water to run off a roof. 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:
The term used to describe the elastic, rubber like properties of a
material. End Lap:
The distance of overlap where one ply extends beyond the end of the
immediately adjacent ply. EPDM:
Ethylene Propylene Diene Monomer (commonly referred to as a "rubber
roof") Epoxy:
A class of synthetic, thermosetting resins that produce tough, hard,
chemical-resistant coatings and adhesives. Equilibrium Moisture Content (EMC):
(1) the moisture content of 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. Expansion Joint:
A structural separation between two building elements designed to
minimize the effect of the stresses and movements of a building's
components and to prevent these stresses from splitting or ridging the
roof membrane. Exposure:
(1) the transverse 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 a 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. Extrusion:
A manufacturing process which consists of forcing batched and formulated
material through an orifice. Fabric:
A woven cloth of organic or inorganic filaments, threads, or yarns. Facer:
A surfacing applied at the factory on some insulation boards. Factory Mutual:
An organization that classifies roof assemblies for their fire
characteristics and wind-uplift resistance for insurance companies in
the United States. Ferrule:
A small metal sleeve placed inside a gutter at the top. A spike is
nailed through the gutter into the fastening board. The ferrule acts as
a spacer in the gutter to maintain its original shape. Field:
The open part of a roof. Fishmouth:
Membrane defect consisting of an opening in the edge lap of a felt in a
built up membranes; a consequence of an edge wrinkle. Flashing:
Components used to weatherproof or seal the roof system edges at the
perimeters, penetrations, walls and other places where the roof covering
is interrupted or terminated. Flashings:
Components that make a watertight seal between the field of a roof and
walls or penetrations. Fully-Adhered:
Installation method where a membrane is totally adhered. Heat Welding:
Heating materials with hot air or a propane torch so they will adhere. Heat Welding:
Method of melting or fusing together the overlapping edges of separate
sheets of thermoplastics and polymer modified bitumen’s. Horizontal Flashing:
Flashings that are installed around objects on the flat surface of a
roof. Hygroscopic:
The term used to describe a material which attract, absorbs and retains
atmospheric moisture. Incline:
The slope of a roof expressed either in percent or in the number of
vertical units of rise per horizontal unit of run. Infrared Thermography:
A practice of roof analysis where an infrared camera is used to measure
the temperature differential of a roof surface to locate areas of
underlying moisture. Inorganic:
Being or composed of matter other than hydrocarbons and their
derivatives, or matter what is not of plant or animal origin. Insulation:
Material that helps keep heat in a building in cold weather. It also
helps keep heat out of a building in hot weather. Insulation:
A material applied to reduce the flow of heat. Inverted Roof Membrane Assembly (IRMA):
A patented, proprietary variation of the "Protected Membrane Roof
Assembly in which Styrofoam Brand insulation and ballast are placed over
the roof membrane. IRMA and Styrofoam are registered trademarks of the
Dow Chemical Corporation. Lap:
That part of a roof or flashing that overlaps or covers any portion of
the same or another type of adjacent component. Life cycle costing:
A method of economic analysis that takes into account expected costs
over the useful life of an asset. Light reflectance:
The percentage of light that is not absorbed by the surface of the
material. Live Loads:
Temporary loads that the roof structure must be designed to support,
(e.g., people, installation equipment, rain, snow, ice, etc.) Loose laid membranes:
Membranes that are not attached to the substrate except at the
perimeter. Typically held in place with ballast. Loose-Laid and Ballasted:
Installation method where a membrane is only attached in a few places.
It is mostly held down by ballast. Low Temperature Flexibility:
The ability of a membrane to remain flexible after it has been cooled to
a low temperature. Low-Slope Roof:
A roof with a slope of 3 inches per foot or less Manufacturer's Bond:
a security company's guarantee that it will stand behind a
manufacturer's liability to finance membrane repairs occasioned by
ordinary wear within a period generally limited to 5, 10, 15, or 20
years. Mechanically Attached:
When material is attached to a deck with screws or other fasteners. Mechanically Fastened:
An installation method where a membrane is attached to a deck with
fasteners. Mechanically Fastened Membranes:
Membranes attached at defined intervals to the substrate. Membrane:
A flexible or semi-flexible roof covering or waterproofing layer, whose
primary function is the exclusion of water. Metal Flashing:
see FLASHING; metal flashing is frequently used as through wall
flashing, cap flashing, counter flashing or gravel stops. Metal Roof System:
A roof system made of metal panels. Modified Bitumen:
Composite sheets consisting of a polymer (e.g., atactic polypropylene
(APP), or styrene butadiene styrene (SBS)) often reinforced and
sometimes surfaced with various types of mats, films, foils and mineral
granules. Moisture Relief Vent:
Venting device through the roofing membrane to relieve moisture vapor
pressure from within the roof assembly. Mole Run:
A meandering ridge in a roof membrane not associated with insulation or
deck joints. Nailable:
When parts of a roof system can be mechanically fastened to a deck. Neoprene:
A synthetic rubber (polychloroprene) used in sheet applied elastomeric
roof membranes or flashings. Night Seal:
Method used to temporarily seal a membrane edge during construction to
protect the roof assembly from water penetration. Non-Vulcanized Membrane:
A membrane manufactured from thermoplastic compounds that retain its
thermoplastic properties throughout its service life. Nuclear Testing:
A device that contains a radioactive source to emit high velocity
neutrons into a roof system. Reflected neutrons are measured to
ascertain presence of moisture. Orange Peel:
A surface condition that shows a fine texture resembling the texture of
an orange. Organic:
Being or composed of hydrocarbons or their derivatives, or matter of
plant, or animal origin. Parapet Wall:
Perimeter wall, which extends above the roof. Peel Strength:
Average force required to peel a membrane from the substrate to which it
has been bonded. Penetration:
Any object passing through the roof. Perlite:
An aggregate used in lightweight insulation concrete and in preformed
perlite insulation boards, formed by heating and expanding siliceous
volcanic. 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 = 0.491 psi). The formula for perm is: P = GRAINS OF WATER
VAPOR/SQUARE FOOT * HOUR * INCH MERCURY Permeance:
An index of a material's resistance to water vapor transmission. (See
PERM.) Phase Application:
The installation of a roof system or waterproofing system during two or
more separate time intervals. Pitch Pocket:
a flange, open bottomed, metal container placed around columns or other
roof penetration that is filled with hot bitumen and/or flashing cement
to seal the joint. Polymers:
Chemical compounds. In modified bitumen roof systems, they are added to
bitumen to change its chemistry. Pond:
A roof surface that is incompletely drained. Ponding:
When water stays on a roof assembly. A roof system is supported by a
deck. Positive Drainage:
The drainage condition in which consideration has been made for all
loading deflection of the deck, and additional roof slop has been
provided to ensure complete drainage of the roof area within 24 hours of
rainfall. Pourable Sealer:
A type of sealant often supplied in two parts and is typically used to
fill pitch pans. Primer:
A thin liquid bitumen applied to a surface to improve the adhesion of
subsequent application of bitumen. Protected Membrane Roof:
An insulated and ballasted roof assembly, in which the membrane is
covered by the insulation and ballasted (sometimes referred to as an
"inverted roof assembly"). Psychometric Chart:
A diagram relating to the properties of humid air with temperature. Purlins:
Metal channels or beams that support a structural metal roof system. PVC:
Polyvinyl Chloride – Usually associated with a thermoplastic single ply
roof membrane system. Rake:
The sloped edge of a roof at the first or last rafter. Re-Cover:
Installing a new roof system on top of an existing roof system. Reflectivity:
The ability of the surface of a material to reflect the infra red energy
of a light source. Reglet:
A groove in a wall or other surface adjoining a roof surface for use in
the attachment of counter flashing. Reinforced Membrane:
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 pound of water
vapor at a given temperature, the relative humidity (RH) is 50 percent. Reroofing:
Installing a new roof system on a building that is not new. Reroofing:
The practice or applying new roofing material over existing roofing
materials. Ridging:
An upward, "tenting" displacement of a roof membrane, frequently
occurring over insulation joints, deck joints and base sheet edges.
Generally associated with improper application. (See picture framing) Roof Assembly:
A roof deck, vapor retarder, insulation and roof membrane. Roof Assembly:
An assembly of interacting roof components (including the roof deck)
designed to weatherproof and, normally, to insulate a building's top
surface. Roof Deck:
The bottom part of a roof assembly. A roof system is supported by a
deck. Roof Membrane:
The watertight part of a system. Roof System:
All the components above the deck. Roof System:
A system of interacting roof components (NOT including the roof deck)
designated to weatherproof and, normally, to insulate a building's top
surface. Rubber:
A polymeric material, which, at room temperature, is capable of
recovering substantially in shape and size after removal of force. R-Value:
The resistance to heat transfer of a material. SBS:
See Styrene Butadiene Styrene Seal:
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. Self Adhering Membrane:
A membrane that can adhere to a substrate and to itself without use of
adhesives. The undersurface is protected by a release paper. Selvage Joint:
A lapped joint designed from membrane. 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. Selvage:
An edge or edging that differs from the main part of a sheet. Shark Fin:
An upward curled felt side or lap or end lap. Shingling:
The procedure of laying parallel sheets so that one longitudinal edge of
each felt overlaps and the other longitudinal edge under laps, an
adjacent sheet. Normally, sheets are shingled on a slope so that the
water flows over rather than against each lap. Single-Ply Systems:
Systems that have only one layer of roofing membrane. Slip Sheet:
A sheet material placed between two components of a roof assembly to
ensure that no adhesion occurs between them, and/or to prevent possible
damage from chemical incompatibility, wearing or abrasion of the
membrane. Often associated with PVC membranes. Slope:
The incline of the roof Slope:
The tangent of the angle between the roof surface and the horizontal. It
is measured in inches per foot. Snow Load:
A load imposed on buildings due to snowfall. (Categorized as live or
environmental load.) Soil Stack:
A sanitation pipe that penetrates the roof – used to vent plumbing
fixtures. (Stink Stacks) Solvent Welding:
A process where a liquid solvent is used to chemically weld or join
together two or more layers of certain membranes (usually
thermoplastics). Sprayed Polyurethane Foam (SPF):
a foamed plastic material, formed by spraying two components, PMDI ([A]
component) and a resin ([B] component) to form a rigid, fully adhered,
water resistant, and insulating membrane. Square:
The term used to describe 100 square feet of roof area. Stress Crack:
External or internal cracks within a material caused by long-term
stress. Stripping:
The technique of taping joints between insulation boards on deck panels. Styrene Butadiene, Styrene Copolymer (SBS):
High molecular weight polymers that have both thermoset and
thermoplastic properties formed by the block copolymerization of styrene
and butadiene monomers. These polymers are used as the modifying
compound in SBS polymer modified roofing membranes to impart rubber like
qualities to the asphalt. Substrate:
The surface upon which the roofing or waterproofing membrane is applies
(i.e. the structural deck or insulation). 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 the roof; (2) provide a gradual
transition from one layer of insulation to another. Tapered Insulation:
Insulation that is made so the material has slope. Taping:
See STRIPPING. Tear Off and Reroof:
The removal of all roof system components down to the structural deck
followed by the installation of a new roof system. Tear Strength:
The maximum force required to tear a specimen. Tear-off:
Removing an existing roof system. Test Cut:
A sample of the roof membrane, usually 4 inches x 40 inches in size,
that is cut from a roof membrane to diagnose the condition of the
existing membrane (e.g., to detect leaks or blisters). Thermal Conductance (C):
A unit of heat flow that is used for specific thickness 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 1 square
foot of 1 inch thick homogeneous material in one hour. Thermal Insulation:
A material applied to reduce the flow of heat Thermal Resistance:
An index of material applied to reduce the flow of heat. Thermal Shock:
The stress producing phenomenon resulting from sudden temperature
changes in a roof membrane. (For example, when a rain shower follows
brilliant, hot sunshine.) Thermoplastic Olefin Membrane (TPO):
A blend of polypropylene and ethylene-propylene polymers. Colorant,
flame retardants, UV absorbers, and other proprietary substances, which
may be blended with the TPO to achieve the desired physical properties. Thermoplastic:
Materials that soften when heated and harden when cooled. Thermoset:
A material that solidifies or "sets" irreversibly when heated. This
property is usually associated with cross-linking of the molecules
induced by heat or radiation. Thermostats and Thermoplastics:
Two types of single-ply membranes. Through Wall Flashing:
A water resistant membrane or material assembly extending through a wall
and its cavities, positioned to direct any water entering the top of the
wall exterior. Tie-Off:
A seal used to terminate a roofing application at to the adjacent
roofing system. TPO:
See Thermoplastic Olefin. Tuck pointing:
Process of removing deteriorated mortar from an existing masonry joint
and troweling new mortar or other filler into the joint. Underlayment:
A material installed between a deck and roof system. Valley:
Area on a roof surface where two downward slopes meet. Vapor Migration:
The movement of water vapor from a region of high vapor pressure to a
region of lower vapor pressure. Vapor pressure Gradient:
A graph, analogous to a temperature gradient, indicating the changes in
water vapor pressure at various cross sectional planes through a roof or
wall system. Vapor Retarder:
Material that helps keep a building’s moisture vapor from getting into
the roof insulation. Vapor Retarder:
A material designed to restrict the passage of water vapor through a
wall or roof. In the roofing industry, a vapor retarder should have a
perm rating of 0.5 or less. 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. Vertical Flashing:
Flashings installed at upturned edges. Waterproofing: Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.
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