the roof of a house

Roofing Glossary

Select a letter


crushed or water worn stone or slag that is used as a protective surface or ballast to anchor loosely laid or protected membrane assemblies

All Weather Elastomeric Mastic

a pliable asphaltic based elastomeric roofing mastic that can be installed in moist or wet conditions


a term describing the cracking and shrinking of asphalt

Application Rate

the quantity per unit a material is applied i.e. 1 gallon per square

Area Divider

a raised detail installed to relieve stress in a roofing system on a roof deck that does not have an expansion join


a natural fibrous silicate material

Asphalt, Roofing

a dark brown to black material that is a residual by product of petroleum distillation


containing or treated with asphalt

Asphalt Felt

an asphalt saturated or coated felt


the practice of mechanically fastening felts in addition to hot-mopping

Base Flashing

the flashing material that covers a cant strip or transition from the roof deck to a vertical surface

Base Ply

the lowermost or first ply of roofing felt installed

Base Sheet

a saturated or coated felt placed as the first ply in a multi-ply roof membrane assembly


an asphaltic type material derived from coal or petroleum


containing or treated with bitumen

Bituminous Emulsion

a suspension of minute globules of bituminous material in water or a water soluble solutions

Bituminous Grout

a mixture of bituminous material and fine sand that flows into place when heated


a small bubble or blister in the flood coat of a gravel surfaced roof system

Blind Nailing

the practice of nailing the back portion of a roofing felt so that the fasteners are not exposed to the weather when the system is completely installed


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


wood built into a roofing system generally above the substrate and around penetrations and perimeter of a deck to act as a nailer for attachment of membrane or flashing and provide a termination method for insulation


the adhesion and cohesive forces holding two roofing components together


embedding a ply of roofing material into an adhesive with a broom or squeegee

Built-Up Roof Membrane

a continuous semi-flexible roof membrane assembly of saturated or coated felts and a bituminous material

Cant Strip

A beveled strip of material that eases the transition between vertical projections in a roof deck

Cap Flashing

A sheet of metal coping installed on the top of a higher wall such as a parapet

Capillarity / Capillary Action

The process of water being absorbed or “wicked” into a reinforcing fiber of a felt which can cause felt delamination

Cap Sheet

A granule surfaced membrane used as the top ply of a built up roofing system


A material that is used to fill a crack or joint, generally remains flexible for an extended period to compensate for expansion

Coal Tar

A dark brown to black material that is the residue from partial evaporation or distillation of coal tar

Coal-Tar Pitch

A coal tar used as a waterproofing agent in low slope or dead-level roofing systems

Coal-Tar Felts

a felt that has been saturated with refined coal tar

Coated Sheet Felt

an asphaltic felt which has been additionally coated with a harder more viscous asphalt

Cold Process Roofing

a built-up roofing system that uses an asphaltic material which does not require heating to be applied


the formation of water from vapor in the air upon contact of a cold surface


the covering piece on top of a wall exposed to the weather, usually sloped to shed water


material usually metal that is installed into or on a vertical surface to cover the top edges of the base flashing material


one layer of a series of materials which make a complete system


the surface area consistently covered by a specific quantity of a particular material


a separation or fracture in a material generally caused by a stress or movement


a false roof generally installed on horizontal roof valleys created by projections such as a chimney, to divert water around the projection. also called a saddle or saddle flashing


a solvent thinned bitumen used in cold process, as a primer or coating


a detail designed to prevent lateral water movement. generally installed as a temporary seal to protect an existing system during reproofing. this detail is always removed.


the treatment of a surface to resist the passage of moisture. this does not prevent the passage of moisture under pressure (hydrostatic pressure)

Dead Level

absolutely level, no slope

Dead-Level Asphalt

an asphalt that has a low softening point (temperature), and flows when warmed in the sun. always installed on dead level decks

Dead Loads

non-moving rooftop loads such as mechanical equipment, air conditioning equipment, or the deck itself


the structural surface to which the roofing system and insulation are installed


Separation of the piles of a roofing system, or the separation of a ply itself

Dew Point

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


the process of applying two layers of aggregate and bitumen to a built-up roof


a device that allows for the flow of water from a roof area


a reduction in the softening point of bitumen that occurs when bitumen is heated in the absence of air

Edge Sheets

felt strips that are cut to a width narrower than a full sheet, used to start the felt shingling pattern at the roof edge

Edge Stripping

application of narrow felt strips to cover the joint between flashing and the built-up roofing system

Edge Venting

the practice of providing regularly spaced protected openings along the roofs edge to provide a means to relieve moisture vapor pressure


a material that returns to it’s approximate size and shape after being subjected to a stress and then released


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


the process of pressing a material into an adhesive

Emergency Repair

a repair which has been installed under adverse conditions to stop water penetration into a building, which must be replaced when weather conditions are more favorable


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


a continuous membrane edge seal formed at the perimeter and at the penetrations by folding the base ply back over the plies to prevent any asphalt seepage from the edges of the membrane

Equiviscous Temperature (EVT)

the recommended temperature of asphalt, plus or minus 25 degrees F at the time of application

Expansion Joint

a structural separation of a roof deck or walls to allow movement


the amount of a roofing material that is left exposed to the elements after installation is complete or the time during which a portion or a roofing element is exposed to the weather


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

Factory Mutual (FM)

an organization that classifies the fire and wind characteristics of materials for insurance companies

Factory Square

108 square feet of roofing material


see “Dropback”


a flexible sheet manufactured by the interlocking or fibers through a combination of mechanical work, moisture, and heat

Felt Layer

a machine used for applying bitumen and built-up roofing felts

Fiber Glass Felt

see “Glass Felt”

Fine Mineral Surfacing

inorganic material used on the surface of roofing, more than 50% of the material must pass a No. 35 sieve test


a half cylindrical or half conical opening formed by edge wrinkles


the system used to seal membrane edges at penetrations or perimeters

Flashing Cement

a trowelable mixture of cutback bitumen and mineral stabilizers including asbestos or other inorganic fibers

Flat Asphalt

see “Dead-Level Asphalt”

Flood Coat

the top layer of the bitumen into which the aggregate is embedded on an aggregate-surface built-up roofing system

Fluid Applied

an elastomeric material, fluid at ambient temperature, that dries or cures after installation to form a continuous membrane. these systems do not generally incorporate a reinforcement membrane

Glass Felt

glass fibers bonded into a sheet with resin and suitable for impregnation in the manufacture of bituminous waterproofing materials, roof membranes, and shingles

Glass Mat

a thin mat composed of glass fibers with or without a binder

Glaze Coat

a thin layer of asphalt which is the top layer of a smooth surface roof or protects inner plies in delayed construction conditions


Coarse, granular aggregate larger than sand, normally occurs due to natural erosion

Gravel Guard

a flanged device usually metal, designed to be a continuous finished edge for roofing material and to prevent loose aggregate from washing off the roof

Gravel Spot

see “Gravel Guard”

Gravel Stop

see “Gravel Guard”


the minimum distance measured at 90 degrees from the eave along the face of a shingle or felt, from the upper edge of the nearest exposed surface

Hot Sheet

a felt that has been installed with hot bitumen

Hot Stuff / Hot

the roofer’s term for hot bitumen


The slope of a roof expressed either in percent or in the number of vertical unites per horizontal unit of run i.e. 4” in 12’ – 4 inches of vertical rise per 12 inches of horizontal run


being composed of materials other than plants or animals


a material which retards the flow of heat or sound

Live Load

moving roof installation equipment, ice, snow, or rain


a trowelable mixture of asphalt, volatile solvent and mineral fillers used as a cold coating in the application of flashing, for sealing around details


a continuous flexible or semi-flexible roof covering that forms the water control element of a roofing system. An open weave fabric that is used to reinforce a waterproofing agent such as mastic


a metallic screen or wire that is used to reinforce stucco or concrete. An open weave fabric that is used to reinforce a waterproofing agent such as mastic

Mineral Fiber Felt

a felt with mineral wool as its primary component

Mineral Granules

see “Fine Mineral Surfacing”

Mineral Stabilizer

a fine water insoluble inorganic material, used in a mixture with solid or semi-solid bituminous materials

Mineral Surfaced Roofing

built-up roofing materials whose top ply consists of a granule surface sheet

Modified Bitumen

a composite sheet consisting of a copolymer modified bitumen often reinforced and surfaced

Mole Run

a meandering ridge in a roof membrane which is not associated with insulation or deck joints

Mop and Flop

an application procedure where a material is placed upside down adjacent to its final installation point and coated with an adhesive then turned over and applied to the substrate


the application of hot bitumen with a mop or mechanical applicator

Nineteen-inch Selvage

a granule surfaced roll material which has a 19 inch smooth portion to allow an overlap when installed, yielding a two-ply” system


a granule surface roll roofing material that is composed or organic felt and has a mass of approximately 90 pounds per 100 square feet

Not To Exceed (NTE)

a pre-approved billing limit established with a client prior to responding and performing work


National Roofing Contractors Association


of plant or animal origin

Parapet Wall

that part of any wall entirely above the roof

Parge Coat

a coating of cementious material to a wall to help resist hydrostatic pressure


an aggregate used in lightweight concrete and in performed insulation boards

Permanent Repair

a repair that has been installed in such a way as to match the existing system and to outlast the surrounding roofing materials

Phased Application

the installation of a system in two or more separate time intervals, requiring nightly cutoffs

Picture Framing

the regular patterning of material around the perimeter of a building or deck joints


see “Coal Tar”

Pitch Pocket

a flanged metal collar device that is placed around penetrations and filled with bitumen, mastic, or a pourable sealer

Plastic Cement

see “Flashing Cement”


a plastic like polymer that can be molded, extruded, or cast into shapes that will soften when heated and harden when cooled


a layer of felt in a built-up roof membrane assembly


an inorganic polymeric material which can be made into fibers that are used as reinforcement felts and fabrics


an area of a roof which does not completely drain water

Positive Drainage

the drainage conditions which allow water to be completely gone within 48 hours after a rainfall


a thin liquid bitumen applied to a surface to improve the adhesion of subsequent bituminous materials

Quoted Price

a fixed price given to a client to perform specific work


the slope edge of a roof at the first and last rafter


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

Re-Entrant Corner

an inside corner of a surface, producing stress concentrations in a roofing or waterproofing system


a groove in a wall or other surface adjoining a roof surface for use in the attachment of counterflashing

Reinforced Membrane

a roofing or waterproofing membrane reinforced with felts, mats, fabrics, or chopped fibers


the corrective materials and actions necessary to stop water from entering through the defect in the roofing system


the corrective materials and actions necessary to bring a neglected roofing system back to it’s best possible condition to extend it’s current life cycle


Roofing Industry Educational Institute

Roof Cement

see “Flashing Cement”

Roof Divider

a building detail used to limit the size of continuous roof membrane, dividing a roof into smaller areas. the divider extends only to the roof deck and is not an expansion joint

Roof Mastic

see “Flashing Cement”


the lateral movement of components of a roofing system


see “Incline”

Smooth-Surfaced Roofing

a roofing system that has been installed and whose top layer has no aggregate or ballast

Softening Point

the temperature at which bitumen begins to soften and flow

Solid Mopping

a continuous mopping of bitumen

Special Steep Asphalt

see “Steep Asphalt”


a membrane tear resulting from tensile strength

Split Sheet

see “Nineteen-Inch Salvage”


The process of removing components or the entirety of a roofing system. Complete tear-offs usually involve stripping the roof down to the decking.

Thermal Imaging Service

A form of leak detection and energy-efficiency audit. It detects and indicates differences in temperature between sections of a rooftop.

Thermoplastic Membrane

A membrane (or ply) molded by the use of extreme heat. Membranes of this variety typically have much stronger seams. Material examples include TPO and PVC

TPO Roofing

Stands for thermoplastic polyolefin. A form of single ply, rubberized roofing that typically comes in a reflective white color.

Two-way Air Vent

Designed to allow limited air flow through a roofing system, lessening the negative effects of negative air flow.


A sheet placed over the surface of roof decking prior to installing the subsequent layers. Protects some protection against moisture infiltration.

Urethane Modified Acrylic Coating

A form of reflective roof coating designed for stronger resistance against water erosion.

Vents/Pipe Stacks

Types of rooftop penetrations, identifiable by their round shape.

Wind Load

The force placed on a building or roof as wind strikes it.

Wind Uplift

The force inflicted on a roofing system when upward pressure (created by wind) is greater than downward pressure. Measured in pounds per square foot.