A
Aggregate: (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.
Asbestos: a group of natural, fibrous, impure silicate materials, sometimes found
in older roofing and other materials. The presence of asbestos can lead to health
hazards, environmental concerns and additional re-roofing construction costs for
testing, abatement and disposal.
Asphalt: A dark brown to black material in which the predominating constituents
are bitumens, which occur in nature or are obtained in petroleum processing.
B
Back nailing: the practice of blind nailing (in addition to hot mopping) all the
plies of a substrate to prevent slippage.
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 Ply: the base ply is the first ply when it is a separate ply and not part of a
shingled system.
Base Sheet: a saturated or coated felt placed as the first ply in some multi-ply
built up roof membranes.
Bitumen: the generic term for an amorphous, semi-solid mixture of complex
hydrocarbons derived from any organic source. Asphalt and coal tar are the two
used in the roofing industry.
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.
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.
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.
Built-up Roof Membrane (BUR): 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 surfaced with
mineral aggregate, bituminous materials, or a granule-surfaced roofing sheet.
C
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.
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.
Cold Process: 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. (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.
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.
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.
D
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.
E
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 placing
a material into another material so that it becomes an integral part of the whole
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")
Equiviscous Temperature (EVT): the temperature at which bitumen attains the
proper viscosity for built up membrane application.
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.
F
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.
Felt: a fabric manufactured from vegetable fibers (organic felts), asbestos fibers
(asbestos felts), or glass fibers (glass fiber felts). The manufacturer process
involves mechanically interlocking the fibers of the particular felt material in the
presence of moisture and heat.
Fishmouth: Membrane defect consisting of an opening in the edge lap of a felt
in a built up membrane; 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.
Flood Coat: the top layer of bitumen into which the aggregate is embedded on
an aggregate-surfaced built up roof.
G
Glass Fiber Felt: A felt sheet in which glass fibers are bonded into the felt sheen
with resin. Glass fiber felts are suitable for impregnation and coating. They are
used in the manufacture and coating of bituminous waterproofing material, roof
membranes, and shingles.
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: coarse, granular aggregate, containing pieces approximately 5/8 inch to
1/2 inch in size and suitable for use in aggregate on built up roofs.
Gravel Stop: a flange devices, frequently metallic, designed to provide a
continuous finished edge for roofing materials and to prevent loose aggregate
form washing off of the roof.
H
Heat Welding: method of melting or fusing together the overlapping edges of
separate sheets of thermoplastics and polymer modified bitumens.
Hot Stuff or Hot: the roofer's term for hot bitumen
I
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.
Insulation: a material applied to reduce the flow of heat.
L
Lap: that part of a roof or flashing that overlaps or covers any portion of the
same or another type of adjacent component.
Lead: a soft workable metal used for miscellaneous flashings.
Life cycle costing: a method of economic analysis that takes into account
expected costs over the useful life of an asset.
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.
M
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 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.
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.
Mopping: an application of hot bitumen applied to the substrate or to the felts of
a built up roof membrane with a mop or mechanical applicator.
N
Nailing: (1) in the Exposed Nail Method, nail heads are exposed to the weather;
(2) in the Concealed Nail Method, nail heads are concealed from the weather.
O
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.
P
Parapet Wall: perimeter wall, which extends above the roof.
Penetration: any object passing through the roof.
Perlite: an aggregate used in lightweight insulation concrete and in preformed
perlitic insulation board, formed by heating and expanding siliceous volcanic.
Phase Application: the installation of a roof system or waterproofing system
during two or more separate time intervals.
Phenolic: a rigid closed-cell foam product with an orange or light red foam core,
sandwiched between various types of facers. Problems have been reported with
board shrinkage, and corrosion of adjacent metal roof assembly components.
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.
Ply: a layer of felt in a built up roof membrane system. A four-ply membrane
system has four plies felt. The dimension of the exposed surface (the "exposure")
of any ply may be computed by dividing the felt width (minus 2 inches) by the
number of plies; thus, the exposed surface of a 36 inch wide felt in a four ply
membrane should be 8 1/2 inches.
Pond: a roof surface that is incompletely drained.
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.
Protected Membrane Roof (PMR): 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").
Primer: a thin, liquid bitumen applied to a surface to improve the adhesion of
subsequent application of bitumen.
PVC: Polyvinyl Chloride – Usually associated with a thermoplastic single ply roof
membrane system.
R
R-Value: the resistance to heat transfer of a material.
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: a roofing or waterproofing membrane reinforced with
felts, mats, fabrics, or chopped fibers.
Re-roofing: 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.
Roll Roofing: the term applied to 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.
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.
S
Saturated Felt: a felt that has been partially saturated with low softening point
bitumen.
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.
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: an edge or edging that differs from the main part of (1) a fabric, or (2)
granule-surfaced roll roofing material.
Shingle: (1) a small unit of prepared roofing material designed to be installed
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 an adjacent felt.
(See PLY.) 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.
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.
Slippage: the relative lateral movement of adjacent components of a built up roof
membrane. It occurs mainly in roof membranes on a slope, sometimes exposing
the lower plies to the weather.
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.
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).
Square: the term used to describe 100 square feet of roof area.
Standing Seam: a metal roof system that consists of an overlapping or
interlocking seam that occurs at an upturned rib.
Substrate: the surface upon which the roofing or waterproofing membrane is
applies (i.e. the structural deck or insulation).
T
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.
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.
Tear Off and Re-roof: 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.
Test Cut: a sample of the roof membrane, usually 4 inches x 40 inches in size,
that is cut from a roof membrane to determine the weight of the average interply
bitumen poundage and/or diagnose the condition of the existing membrane (e.g.,
to detect leaks or blisters).
Thermal Insulation: a material applied to reduce the flow of heat
Thermal Shock: the stress producing phenomenon resulting from sudden
temperature changes in a roof membrane.
Thermoplastic: materials that soften when heated and harden when cooled.
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.
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.
Tuck pointing: process of removing deteriorated mortar from an existing
masonry joint and troweling new mortar or other filler into the joint.
U
Underwriters Laboratories: an organization that classifies roof assemblies for
their fire characteristics and wind uplift resistance for insurance companies in the
United States.
V
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 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.
Vermiculite: an aggregate used in lightweight insulation concrete, formed by the
heating and consequent expansion of a micaceous mineral.
W
Waterproofing: treatment of a surface or structure to prevent the passage of
water under hydrostatic pressure.
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