crushed stone, crushed slag or water worn gravel used for surfacing a built-up roof. Any granular mineral material.

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.

a group of natural, fibrous, impure silicate materials.

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 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 cool.

the cavity or open space above the ceiling and immediately under the roof deck of a steep-sloped roof.


Base Ply
the lower most ply of roofing material in a roof assembly.

Base Sheet
a heavy felt that is used as the first ply in a modified bitumen roof system.

(1) a class of amorphous, black or dark colored, (solid, semisolid 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.

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).

an enclosed pocket of air mixed with water or solvent vapor, trapped between impermeable layers of felt, or between the felt and substrate.

the adhesive and cohesive forces holding two roofing components in intimate contact.

British Thermal Unit (BTU)
the heat energy required to raise the temperature of 1 pound of water 1 degree Fahrenheit.

an upward, elongated tenting displacement of a roof membrane frequently concurring over insulation of 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, country, state, etc.). Building codes control design, construction, and quality of materials, use and occupancy, location and maintenance of building and structures within the area for which the code has been adopted.

Built-Up Roof Membranes
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. (Abbreviation: BUR)

an individual package of shakes or shingles.


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.

Cap Flashing
usually composed of metal, used to cover or shield the upper edges of the membrane base flashing, wall flashing, or primary flashing.

Cap Sheet
a granule-surfaced coated sheet used as the top ply of a built-up roof membrane or flashing.

a composition of vehicle and pigment, used at ambient temperatures for filling joints, that remains plastic for an extended time after application.

Chalk Line
a line made on the roof by snapping a taut string or cord dusted with colored chalk. Used for alignment purposes.

stone, masonry, prefabricated metal, or a wood framed structure, containing one or more flues, projecting through and above the roof.

an upward extension of enclosed space created by carrying a setback vertical, wall (typically glazed) up and through the roof slope. Two intersecting shed roof on different planes.

Clipped Gable
a gable cutback at the peak in the hip-roof form.

Closed-Cut Valley
a method of valley application in which shingles from one side of the valley extend across the valley while shingles from the other side are trimmed back approximately 2 inches from the valley centerline.

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.

the conversion of water vapor or other gas to liquid as the temperature drops or the atmospheric pressure rises.

the covering piece on top of a wall exposed to the weather, 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.

(1) the term used for each application of material that forms the waterproofing system or the flashing; (2) one layer of a series of material 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.)

the surface area continuously covered by a specific quantity of a particular roofing material.

a separation or fracture occurring in a roof membrane or roof deck, generally caused by thermal induced stress or substrate movement.

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.

a relatively small, elevated area of a roof constructed to divert water.

Cross Ventilation
the effect that is provided when air moves through a roof cavity between the vents.

(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.

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.

the open portions of a strip shingle between the tabs.


Dead Level
absolutely horizontal, or zero slope.

Dead Loads
nonmoving rooftop loads, such as mechanical equipment, air conditioning units, and the roof deck itself.

Dead Valley
an area where a low slope internal angle is formed by the intersection of at least 2 sloping roof planes where there is a good chance of standing water.

the structural surface to which the roofing or waterproofing system is applied.

the surface – usually plywood or oriented-strand board (OSB) – to which roofing materials are applied.

separation of the plies in a roof membrane system or separation of laminated layers of plywood.

Dew Point
the temperature at which water vapor starts to condense in cooling air at the existing atmospheric pressure and vapor content.

Dimensional Shingle
A shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect.

a roof that is shaped like a half-circle, or a variation of one.

a structure projecting from a sloping roof usually housing a window or ventilating louver.

a device that allows for the flow of water from a roof area.
Drip Edge
an L-shaped strip (usually metal) installed along the edges of the roof to allow water run-off to drip clear of the deck, eaves and siding.

Dry-In or Dry-In Felt
usually the underlayment or the process of applying the underlayment for steep roofing.


the lower edge of a sloping roof that projects beyond the wall.

see Gutter. Edge Venting
the practice of providing regularly spaced protected opening along a roof perimeter to relieve moisture vapor pressure.

EPDM Roof Membranes
is a thormoset single-ply membrane. EPDM stands for ethylene propylene diene monomer. This is a rubber roof membrane.

the property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion).

a rubber like synthetic polymer that will stretch when pulled and will return quickly to its original shape when released.

(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.

the homogeneous dispersion of an organic material and water achieved by using a chemical or clay emulsifying agent.

End Lap
the distance of overlap where one ply, pane, or piece extends beyond the end of the immediately adjacent underlying ply, panel, or piece.

Ethylene propylene diene monomer (see also Ethylene propylene diene terpolymer.)

Exhaust Ventilation
air that is vented or exhausted from the roof cavity, typically through vents installed on the up slope portion of the roof. For example, with most steep-slope roof assemblies, exhaust vents are typically located at or near the ridge.

Expansion Joint
a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

(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.

a process in which heated or unheated material is forced through a shaping orifice (a die) in one continuously formed shape, as in film, sheet, rod or tubing.

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.


a woven cloth of organic or inorganic filaments, threads or yarns.

any lightening of initial color.

Fire Rating
the Underwriters Laboratories (UL) system for classifying the fire-resistance of various materials. Roofing materials are rated “Class A,” “B” or “C,” with “A” materials having the highest resistance to fire originating outside the structure.

(1) in steep-slope roofing, a board that is nailed to the ends of a roof rafter; sometimes supports a gutter; (2) in a low-slope roofing, the vertical or steeply sloped roof or trim located at the perimeter of a building. Typically, it is a border for the low-slope roof system.

any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips, and bolts, which may be used to secure various components of a roof assembly.

a flexible sheet manufactured by the inter locking of fibers through a combination of mechanical work, moisture and heat. Felts are manufactured principally from vegetable fibers (organic felts), or glass fibers (glass fiber felts); other fibers may be present in each type.

a metal sleeve placed inside a gutter at the top. A spike or screw is nailed / screwed through the gutter face and ferrule into the fascia board to hold the gutter in place. The ferrule acts as a spacer in the gutter to maintain its original shape.

Field of Roof
the central or main portion of a roof, excluding the perimeter and flashing.

a relatively inert ingredient added to modify physical characteristics.

Fish mouth
(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.

pieces of metal used in a system 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 counter flashing shields the upper edges of the base flashing.

Flashing Collar
(sometimes referred to as a pipe jack or roof jack) an accessory flashing used to cover and / or seal soil pipe vents and other penetrations through the roof.

Flood Coat
the top layer of bitumen into which the aggregate is embedded on an aggregate-surfaced built-up roof.


the vertical triangular portion of the end of a building having a double-sloping roof, from the level of the eaves to the ridge of the roof.

Gable-Shaped Roof
a single-ridge roof that terminates at gable end(s).

to coat steel or iron with zinc.

Ring something like rubber used to cover and/or seal something like metal penetrating metal.

Glass Mat
a mat composed of glass fibers with or without a binder.

course, granular aggregate, with pieces larger than sand grains, resulting from the natural erosion of rock.

Gravel Stop
a flanged device, frequently metallic, designed to provide a continuous finished edge for roofing material and to prevent loose aggregate from washing off the roof.

Grout V
of cement, sand, and water used to fill cracks and cavities in masonry.

a channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.


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.

Torch down is installed using heat from a propane torch to melt the bitumen on the back of a sheet. It adheres to a substrate when it cools.

the inclined external angle formed by the intersection of two sloping roof planes.

Hip Roof
a roof that rises by inclined planes to form one or more hips.

“Hot Stuff” or “Hot”, the roofer’s term for hot bitumen.


Ice Dam
a mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by re-freezing meltwater at the overhang of a steep roof, causing ice and water to back up under roofing materials.

in roofing materials manufacture, to completely surround the fibers in a felt or mat with bitumen, with the spaces between the fibers partially or completely filled without a continuous coating of bitumen on the surface.

the slope of a roof expressed either in percent or in the number of vertical units of rise per horizontal unit of run.

being or composed of matter other than hydrocarbons and their derivatives, or matter that is not of plant or animal origin.

Intake Ventilation
the fresh air that is drawn into a passive ventilation system through vents typically installed in the soffit or eave of a roof.

a felt, metal, or membrane sheet material used between courses of steep-slope roofing to improve the weather and water-shedding characteristics of the primary roof covering during times of wind-driven precipitation. Typically used with wood shakes.

Interlocking Shingles
being or composed of matter other than hydrocarbons and their derivatives, or matter that is not of plant or animal origin.



(Roofing Slang) that space between 2 wood shakes, or that gap or cutout between roofing shingle tabs.


to join layers of materials together using fusion; the process of joining layers of materials together using adhesion.

Laminated Shingles
see Dimensional shingles or Architectural shingles.

that part of a roofing, waterproofing, or flashing component that overlaps or covers any portion of the same or another type of adjacent component.

Lap Cement
an asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing.

a soft malleable, heavy metal; has low melting point and a high coefficient of thermal expansion.

Light Reflectance
the percentage of light that is not absorbed by the surface of a material.

Live Loads
moving roof installation equipment, wind, snow, ice or rain.

Low Slope Application
type of application of roofing on a slope as low as 2/12 pitch, double felt and sealing edges.


a decorative steep-sloped roof on the perimeter of a building.

Mansard Roof
a steeper roof that terminates into a flat roof at its high point.

construction, usually set in mortar, of natural building stone or manufactured units, such as brick, concrete block, adobe, glass block, tile, manufactured stone or gypsum block.

a thick adhesive material used as a cementing agent for holding waterproofing membrane in place.

a thin layer of woven, non-woven, or knitted fiber that serves as reinforcement to the material or membrane.

a flexible or semi-flexible roof covering or waterproofing layer, whose primary function is the exclusion of water.

Metal Flashing
accessory components fabricated from sheet metal and used to weatherproof terminating roof covering edges. Frequently used as through-wall flashing, cap flashing (coping), counterflashing, step-flashing, etc. (See Flashing.)

a superficial growth produced on organic matter or living plants by fungi.

Mineral Granules
opaque, natural, or synthetically colored aggregate commonly used to surface cap sheets, granule-surfaced sheets, and roofing shingles.

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
a modified bitumen membrane roof system is typically composed of factory-fabricated composite sheet consisting of a copolymer modified bitumen which is typically reinforced and installed in one or more plies. The modified sheets are typically fully – adhered by heat welding (torching).

an application procedure in which roofing elements (insulation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate location, are coated with adhesive, and are then turned over and applied to the substrate.

the application of hot bitumen with a mop or mechanical applicator to the substrate or to the felts of a built-up roof membrane.


a synthetic rubber (polychloroprene) used in liquid-applied and sheet applied elastomeric roof membrane or flashings.

(1) the installation of new metal roof deck directly on top of existing metal roof deck;
(2) a method of re-routing with new asphalt shingles over existing shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle.

Net Free Vent Area
the area (measured in square inches) open to unrestricted air flow and commonly used as a yardstick to measure relative vent performance; the area of the opening of a vent minus the area displaced by the screening material.

a prepared organic felt roll roofing with a granule surfaced exposure that has a mass of approximately 90 pounds per 100 square feet.


Open / Skip Sheathing
See Spaced Sheathing.

Open Valley
a method of valley construction in which the steep-slope roofing on both sides are trimmed along each side of the valley, exposing the valley flashing.

being or composed of hydrocarbons or their derivatives, or matter of plant or animal origin.

undesirable depositions of airborne spray.


Parapet Wall
that part of any wall entirely above the roof.

(1) any construction (e.g., pipes, conduits, HVAC supports) passing through the roof.

the capacity of a porous material to conduct or transmit fluids.

an accessory flashing used to cover and/or seal pipe vents and other penetrations.

see Roof Slope

Pitch Change
where one or more angles or pitches come together either at one spot or along the roof surface parallel to the gutters.

Pitch-Pocket (Pitch-Pan)
a flanged, open bottomed enclosure made of sheet metal or other material, placed around a penetration through the roof, filled with grout and bituminous or polymetric sealants to seal the area around the penetration.

Plastic Cement
a roofing industry generic term used to describe asphalt roof cement that is a trowelable mixture of solvent-based bitumen, mineral stabilizers, and other fibers and/or fillers. Generally, intended for use on relatively low slopes, not vertical surfaces.

a layer of felt in a built-up roof membrane system. A four-ply membrane system has four plies of felt.

Polymer Modified Bitumen
see Modified bitumen.

the excessive accumulation of water at low-lying areas on a roof that remains after the 48 hours after the end rainfall under conditions conducive to drying.

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.

a thin, liquid bitumen applied to a surface to improve the adhesion of subsequent applications of bitumen.



one of a series of sloped structural members, that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads.

the slope edge of a roof at the first or last rafter.

a method of asphalt shingle application, also referred to as the straight-up method, whereby shingle courses are applied vertically, up the roof rather than laterally or across and up.
Rake-Starter (Bleeder Strip)
starter-strip used along rake edges in conjunction with asphalt shingle roofing.

the process of covering an existing roofing system with a new roofing system.

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 is 50 percent.

the practice of removing an existing roof system and replacing it with a new roofing system.

the process of re-covering or replacing an existing roofing system.

highest point on the roof, represented by a horizontal line where two roof areas intersect, running the length of the area. Insert scan here.

Ridge Cap
a material or covering applied over the ridge of a roof.

Ridge Vent
a ventilator located at the ridge that allows the escape of warm and/or moist air from the attic area or rafter cavity.

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.

The Resistance to heat transfer of a material. Insulators have relatively high R values.

Roof Jack
a metal or wood bracket used to support toe-boards on steep-slope roofs. (Also see Flashing Collar.)

Roof Overhang
a roof extension beyond the exterior wall of a building.

Roof Slope
the angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as run).


a small tapered/sloped roof area structure that helps to channel surface water to drains. Frequently located in valley. A saddle is often constructed like a small hip roof or pyramid with a diamond-shaped base. (See Cricket.)

Saturated Felt
a felt that has been saturated with low softening point bitumen.

an apparatus with circular apertures for separating sizes of materials.

a hatch that provides access to the roof from the interior of the building.

(1) a generic term for a function that prevents or controls the passage of water; (2) to secure a roof or structure from the entry of moisture.

a coating designed to prevent excessive absorption of finish coats into porous surfaces; a coating designed to prevent bleeding.

a joint formed by mating two separate sections of material. Seams can be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape, sealant, etc.

Self-Sealing Shingle
an asphalt shingle containing factory-applied strip or spots of heat sensitive adhesive intended to adhere the overlying shingle once installed on the roof and warmed by the sun. V Selvage
an edge or edging that differs from the main part of (1) a fabric, or (2) granule-surfaced roll roofing material.

Selvage Edge
an edge designed for certain sheet good materials, e.g., mineral-surfaced sheets. With mineral surfaced sheets, the surfacing is omitted over a portion of the longitudinal edge of the sheet (e.g., mineral surface cap sheet) in order to obtain better adhesion of the overlapping sheet.

The boards or plywood which are fastened to the roof rafters to cover the house.

material used to cover or lane a surface.

Shed Roof
a roof having only one sloping plane and no hips, ridges or valleys.

Shelf Life
the maximum time a package material can be stored under specified conditions and still meet the performance requirements specified.

(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

(1) the procedure of laying parallel felts so that one longitudinal edge of each felt overlaps and the other longitudinal edge under laps, an 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.

a roof having only one sloping plane and no hips, ridges or valleys.

Side Lap
the continuous longitudinal overlap of neighboring like materials.

the bottom horizontal framing member of an opening, such as below a window or door.

Sill Flashing
a flashing of the bottom horizontal framing member of an opening, such as below a window or door.

Single-Ply Membranes
roofing membranes that are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers.

Single-Ply Roofing
a roofing system in which the principal roof covering is a single layer flexible membrane often of thermostat or thermoplastic membrane.

an opening in a roof that is glazed with a transparent or translucent material; used to admit diffused light to the space below.

a hard, brittle metamorphic rock consisting mainly of clay minerals, used extensively as dimensional stone for steep roofing and in granular form as surfacing on some other roofing materials.

relative lateral movement of adjacent components of a built-up membrane, It occurs mainly in roofing membranes on a slope, sometimes exposing the lower plies or even the base sheet to the weather.

the angle of incline, usually expressed as a ratio of rise to run, or as an angle. (See Roof slope.)

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.

Snow Load
the live load due to the weight of snow on a roof; included in design calculations.

the exposed undersurfaces of any exterior overhanging section of a roof eave.

Soffit Vent
a premanufactured or custom built air inlet source located at the downslope eave or in the soffit of a roof assembly.

Softening Point
the temperature at which bitumen becomes soft enough to flow.

Spaced Sheathing
See Spaced Skip Sheathing.

Spaced Skip Sheathing
Type of deck surface used for roofing with wood shakes and wood shingles. Instead of a solid deck like plywood this deck has empty spaces between the boards. This space enables the wood shake or wood shingles to dry out from within. If the wood shake or wood shingle, are removed & neither are replaced, a new plywood or OSB deck is required prior to re-roofing. For example a 1″ X 6″ with a 3″ space then another 1″ X 6″ and another 3″ space. This is followed throughout the entire roof structure.

a precise statement of a set of requirements to be satisfied by a material, product, system, or service.

a membrane tear resulting from substrate or membrane stress.

the process of removing the roofing aggregate and most of the bituminous top coating by scraping and chipping.

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.

Standing Seam
in metal roofing, a type of seam between adjacent sheets of material made by turning up the edges of two adjacent metal panels and then folding or interlocking them in a variety of ways.

Starter Course
the first layer of roofing, applied along a line adjacent to the downslope perimeter of the roof area. With steep-slope watershedding roof coverings, the starter course is covered by the first course.

Starter Strip
roll roofing or shingle strips applied along the downslope eave line before the first course of roofing and intended to fill spaces between cutouts and joints of the first course.

Static Load
any load, as on a structure, that does not change in magnitude or position with time.

Steep-Slope Roofs
a roof of suitable slope to accept the application of water shedding roofing materials.

Steep-Slope Roofing
a category of roofing that includes water shedding types of roof coverings installed on slopes exceeding 3 12 or 25%.

a tower or spire, usually located on a church.

Step Flashing
individual pieces of sheet metal material used to flash walls, around chimneys, dormers and such projections along the slope of a roof. Individual pieces are overlapped and stepped up the vertical surface.

the surface upon which the roofing or waterproofing membrane is applied.

an intentional depression around a drain.


the exposed portion of strip shingles defined by cutouts.

a brown or black bituminous material, liquid or semisolid 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 Strength
the maximum force required to tear a specimen. Tensile strength: Definition: the strength of a material under tension as distinct from torsion, compression or shear.

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 existing membrane.

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 when, for example, a rain shower follows brilliant sunshine.

(1) a volatile liquid added to an adhesive or coating material to modify the consistency or other properties;
(2) a liquid used to clean equipment or other surfaces.

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.

(in roofing and waterproofing) the transitional seal used to terminate a roofing or waterproofing application at the top or bottom of flashings, or by forming a watertight seal with the substrate, membrane or adjacent roofing or waterproofing system.

Tongue and Groove Planks
one of the oldest types of dimensional structural wood used as roof decking. The sides are cut with convex and concave grooves so adjacent planks may join in alignment with each other to form a uniform roof deck.

Torch Down
See Modified Bitumen

The engineered components which have supplemented rafters in many newer houses. They are designed for specific applications and cannot be cut or altered in any way.

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.

a small tower projecting from a building usually at a corner, around with a dome roof.


an asphalt-saturated felt or other sheet material (may be self-adhering) installed between the roof deck and the roof covering, usually used in a steep-slope roof construction. Underlayment is primarily used to separate the roof covering from the roof deck, to shed water and to provide secondary weather protection for the roof area of the building.


the internal angle formed by the intersection of two sloping roof planes.

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.

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.

the resistance of a material to flow under stress. For bitumen, measured in centipoise. (See Viscous.)

resistant to flow under stress. Void: Definition: an open space or break in consistency.


Water Table
the level within the ground, below which the soil is saturated with water.

the quality of a membrane, membrane material, or other component to prevent water entry.

treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

Weep Holes
small openings whose purpose is to permit drainage of water that accumulates inside a building component (e.g., a brick wall, skylight frame, etc.).

to join pieces of metal together by heat fusion.

a condition where free water is present in a substance.

the process of moisture movement by capillary action.

Wind Load
force exerted by the wind on a structure or part of a structure.

Wind Uplift
the force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface.

being in or facing the direction toward which the wind is blowing. The side exposed to the prevailing wind.

Woven Valley
a method of valley construction in which shingles or roofing from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied.




a hard blush white metal, brittle at normal temperatures, very malleable and ductile when heated; not subject to corrosion; used for galvanizing sheet steel and iron, in various metal alloys, and as an oxide for white paint pigment.