Glossary of Roofing Terms
Absorption: the
ability of a material to accept within its body quantities of gases or liquid,
such as moisture.
Accelerated Weathering: the process in which materials
are exposed to a controlled environment where various exposures such as heat,
water, condensation, or light are altered to magnify their effects, thereby
accelerating the weathering process. The material's physical properties are
measured after this process and compared to the original properties of the
unexposed material, or to the properties of the material that has been exposed
to natural weathering.
Acrylic Coating: a coating system based on an acrylic
resin. Generally, a latex-based coating system which cures by air drying.
Acrylic Resin: polymers of acrylic or methacrylic
monomers. Often used as a latex base for coating systems.
Active: will corrode in the presence of moisture or a
"noble" metal.
Adhere: to cause two surfaces to be held together by
adhesion, typically with asphalt or roofing cements in built-up roofing and
with contact cements in some single-ply membranes.
Adhesion: the state in which two surfaces are held together
by interracial forces which may consist of molecular forces or interlocking
action, or both.
Aggregate: rock, stone, crushed stone, crushed slag,
water-worn gravel or marble chips used for surfacing and/or ballasting a roof
system.
Aging: the effect on materials that are exposed to an
environment for an interval of time.
Air Leakage: (as it relates to passive ventilation) negative
condition where air leaks into the roof cavity (designed for use as a passive
ventilation system) through cracks or openings in the structure in lieu of
through the intended intake vents.
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.
Aluminized Steel: sheet steel with a thin aluminum coating
bonded to the surface to enhance weathering characteristics.
Aluminum: a non-rusting metal sometimes used for metal
roofing and flashing.
Ambient Temperature: the temperature of the air;
air temperature.
APP: see Atactic
Polypropylene.
Application Rate: the quantity (mass, volume, or thickness)
of material applied per unit area.
Apron Flashing: a term used for a flashing located at the
juncture of the top of the sloped roof and a vertical wall or steeper-sloped
roof.
Architectural Panel: a metal roof panel, typically
a double standing seam or batten seam; usually requires solid decking
underneath and relies on slope to shed water.
Architectural Shingle: shingle that provides a
dimensional appearance.
Area Divider: a raised, flashed assembly (typically a
single- or double-wood member attached to a wood base plate) that is anchored to
the roof deck. It is used to relieve thermal stresses in a roof system where an
expansion joint is not required, or to separate large roof areas (sometimes
between expansion joints), and may be used to facilitate installation of
tapered insulation. (See NRCA
Construction Details.)
ARMA: Asphalt Roofing Manufacturers Association
Asbestos: a group of natural, fibrous, impure silicate
materials used to reinforce some roofing products.
Asphalt: a dark brown or black substance found in a natural
state or, more commonly, left as a residue after evaporating or otherwise
processing crude oil or petroleum. Asphalt may be further refined to conform to
various roofing grade specifications:
» Dead-Level Asphalt: a
roofing asphalt conforming to the requirements of ASTM Specification D 312,
Type I.
» Flat Asphalt: a
roofing asphalt conforming to the requirements of ASTM Specification D 312,
Type II.
» Steep Asphalt: a
roofing asphalt conforming to the requirements of ASTM Specification D 312,
Type lilt
»
Special
Steep Asphalt: a roofing asphalt conforming to the requirements
of ASTM Specification D 312, Type IV.
Asphalt, Air Blown: produced by blowing air
through molten asphalt held at an elevated temperature, to raise the asphalt's
softening point and modify other properties.
Asphalt Emulsion: a mixture of asphalt particles and an
emulsifying agent such as bentonite clay and water.
These components are combined by using a chemical or a clay emulsifying agent
and mixing or blending machinery.
Asphalt Felt: an asphalt-saturated and/or an
asphalt-coated felt. (See Felt.)
Asphalt Primer: see Primer.
Asphalt Roof Cement: a trowelable
mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or
fillers. Classified by ASTM Standard D 2822-91 Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos-Free, Types I and 11
» Type I
is generally referred to as "plastic cement," and is made from
asphalt characterized as self-sealing, adhesive and ductile, and conforming to
ASTM Specification D 312, Type l; Specification D 449, Types I or Il; or
Specification D 946. (See Plastic Cement and Flashing Cement.)
»
Type II is generally referred to as
"vertical-grade flashing cement," and is made from asphalt characterized
by a high softening point and relatively low ductility, and conforming to the
requirement of ASTM Specification D 312, Types II or lil;
or Specification D 449, Type lilt (See Plastic Cement and Flashing Cement.)
ASTM: American Society for Testing and Materials
Atactic Polypropylene: a
group of high molecular weight polymers formed by the polymerization of
propylene.
Attic: the cavity or open space above the ceiling and
immediately under the roof deck of a steep-sloped roof.
Back-Nailing: (also referred to as
Blind-Nailing) the practice of nailing the back portion of a roofing ply, steep
roofing unit, or other components in a manner so that the fasteners are covered
by the next sequential ply, or course, and are not exposed to the weather in
the finished roof system.
Back-Surfacing: fine mineral matter applied to
the back side of asphalt shingles and roll roofing to keep them from sticking
together while packaged.
Ballast: an anchoring material, such as
aggregate, or precast concrete pavers, which employ
the force of gravity to hold (or assist in holding) single-ply roof membranes
in place.
Bar
Joist: see
Steel Joist
Barrel
Vault: a
building profile featuring a rounded profile to the roof on the short axis, but
with no angle change on a cut along the long axis.
Base
Flashing (membrane base flashing): plies or strips of roof membrane material used to
close-off and/or seal a roof at the roof-to-vertical intersections, such as at
a roof-to-wall juncture. Membrane base flashing covers the edge of the field
membrane. (Also see Flashing.)
Base
Ply: the
lowermost ply of roofing in a roof membrane or roof system.
Base
Sheet: an
impregnated, saturated, or coated felt placed as the first ply in some
multi-ply built-up and modified bitumen roof membranes.
Batten: (1) cap or cover; (2) in a metal
roof: a metal closure set over, or covering the joint between, adjacent metal
panels; (3) wood: a strip of wood usually set in or over the structural deck,
used to elevate and/or attach a primary roof covering such as tile; (4) in a
membrane roof system: a narrow plastic, wood, or metal bar which is used to
fasten or hold the roof membrane and/or base flashing in place.
Batten
Seam: a
metal panel profile attached to and formed around a beveled wood or metal
batten.
Bentonite: a
clay, formed from decomposed volcanic ash, with a high content of the mineral montmorillonite; has the capacity of absorbing a
considerable amount of water, and swells accordingly.
Bi-Level Drain: see Dual-Level Drain.
Bird
Bird Screen: wire mesh used to prevent birds
from entering the building through ventilators, louvers, or other openings.
(See Insect Screen.)
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 petroleum
asphalts, coal tars and pitches, wood tars and asphalts; (2) a generic term
used to denote any material composed principally of bitumen, typically asphalt
or coal tar.
Bitumen-Stop: see Envelope and Bleed Sheet.
Bituminous Emulsion: a suspension of minute particles
of bituminous material in water or other aqueous solution. (See Asphalt
Emulsion.)
Blackberry (sometimes referred to
as Blueberry or Tar-Boil): a small bubble or blister in the flood coating of an
aggregate-surfaced built-up roof membrane.
Blanket (Bats) Insulation: fiberglass or other compressible
fibrous insulation, generally available in roll form.
Bleed-Sheet: a sheet material used to prevent
the migration of bitumen.
Bleeder Strip: see Rake-Starter.
Blind-Nailing: the use of nails that are not
exposed to the weather in the finished roofing system.
Blister: an enclosed pocket of air, which
may be mixed with water or solvent vapor, trapped between impermeable layers of
felt or membrane, or between the membrane and substrate.
Blocking: sections of wood (which may be
preservative treated) built into a roof assembly, usually attached above the
deck and below the membrane or flashing, used to stiffen the deck around an
opening, act as a stop for insulation, support a curb, or to serve as a nailer for attachment of the membrane and/or flashing.
Blowing Agent: an expanding agent used to produce
a gas by chemical or thermal action, or both, in manufacture of hollow or
cellular materials.
Bond: the adhesive and/or cohesive
forces holding two components in positive contact.
Bond, Chemical: adhesion between surfaces, usually
of similar materials, resulting from a chemical reaction or cross-linking of
polymer chains.
Bond, Mechanical: adhesion between surfaces
resulting from interracial forces or a physical interlocking.
Bonding Agent: a chemical substance applied to a
suitable substrate to create bond between it and a succeeding layer.
Boot: (1) a covering made of flexible
material, which may be preformed to a particular shape, used to exclude dust,
dirt, moisture, etc. from around a penetration; (2) a flexible material used to
form a closure, sometimes installed at inside and outside corners.
Brake: hand- or power-activated
machinery used to form metal.
Bridging: (1) when the membrane is
unsupported at a juncture; (2) bridging in steep-slope roofing is a method of reroofing over standard-sized asphalt shingles with
metric-sized asphalt shingles.
British Thermal Unit (BTU): the heat energy required to
raise the temperature of one pound of water one degree Fahrenheit (joule).
Brooming: an
action carried out to facilitate embedment of a ply of roofing material into
hot bitumen by using a broom, squeegee, or special implement to smooth out the ply
and ensure contact with the bitumen or adhesive under the ply.
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 the roof assembly.
Building Code: published regulations and
ordinances established by a recognized agency prescribing design loads,
procedures, and construction details for structures. Usually applying to
designated jurisdictions (city, county, state, etc.). Building codes control
design, construction, and quality of materials, use and occupancy, location and
maintenance of buildings and structures within the area for which the code has
been adopted.
Built-Up Roof Membrane (BUR): a continuous, semi-flexible
multi-ply roof membrane, consisting of plies or layers of saturated felts,
coated felts, fabrics, or mats between which alternate layers of bitumen are
applied. Generally, built-up roof membranes are surfaced with mineral aggregate
and bitumen, a liquid-applied coating, or a granule-surfaced cap sheet.
Bundle: an individual package of shakes or
shingles.
Butt Joint: a joint formed by adjacent,
separate sections of material, such as where two neighboring pieces of
insulation abut.
Button Punch: a process of indenting two or more
thicknesses of metal that are pressed against each other to prevent slippage
between the metal.
Butyl: 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.
Butyl Coating: an elastomeric
coating system derived from polymerized isobutylene. Butyl coatings are
characterized by low water vapor permeability.
Butyl Rubber: a synthetic elastomer
based on isobutylene and a minor amount of isoprene. It is vulcanizable
and features low permeability to gases and water vapor.
Butyl Tape: a sealant tape sometimes used
between metal roof panel seams and end laps; also used to seal other types of
sheet metal joints, and in various sealant applications
