Glossary of Roofing Terms & Definitions

Our hope is that when you speak to a roof contractor, either us or another company, that you will be able to understand some of the terminology used. By including this glossary on our site, we sincerely hope you obtain a little bit of knowledge and understanding about your roof system. The better informed you are, the better choices you can make regarding your roof.

Abrasion Resistance

Ability of the roof material to resist being worn from abrasive contact, such as foot traffic, flying debris, tree limbs, mechanical equipment, etc


Capability of material to accept quantities of liquid and gas, usually water


To bond two surfaces together


The state and degree of attachment between two surfaces


A bonding substance that keeps two surfaces attached


Crushed stone or slag, or water worn gravel used to top a built up roof; any granular mineral material


The effect of the weather and environment have on exposed material for a period of time


Rooftop fungus causing dark brown or black stains


Resembling the cracks of an alligator hide on the surface of bitumen built up roof; the cracks may or may not go through the surface of the bitumen

Aluminized Steel

Sheet steel with a layer of aluminum to prevent rusting


Metal sometimes used for flashing and metal panels that does not rust

Ambient Temperature

Air temperature

Angled Fasteners

Roofing nails driven in at an angle and not parallel to the roof deck


American National Standards Institute


Atactic polypropylene; a modified bitumen membrane that can be smooth or granulated and is typically installed by torch down, but may also be applied by cold process adhesives

Application Rate

Amount of material applied per unit area

Apron Flashing

Metal flashing used at chimney fronts; metal flashing used where a sloped roof and wall or steeper sloped roof meet

Architectural Panel

Metal roof paneling usually requiring a solid deck underneath and a slope to shed water off

Architectural Shingle

Also known as dimensional shingles; shingles that provide a three-dimensional appearance

Area Divider

Used to separate large roof areas to accommodate building movement or roof systems with incompatible materials; may used to assist in the installation of a tapered insulation system; is a single or double wood member attached to a properly flashed wood base plate anchored to the roof deck


Asphalt Roofing Manufactures Association


A group of natural, fibrous impure silicate minerals and materials used to resist heat and corrosion


American Society of Home Inspectors


A black or dark brown material obtained through petroleum or crude oil processing used in various types of roofing materials

Asphalt Felt

Used as underlayment; felt paper that has been saturated with or coated with asphalt

Asphalt Primer

Asphalt based primer used to ready material for asphalt sealant

Asphalt Roof Cement

Can be used for temporary roof repairs on asphalt based flat roofs; is a mixture of solvent based bitumen, mineral stabilizers, other fibers, and/or fillers; is trowel grade and used on asphalt compatible materials to waterproof; is divided into two standards: ASTM D2822 is applicable to material containing asbestos; ASTM D4586 is applicable to asbestos free material; can be classified as Type I or Type II; Type I is self-sealing, adhesive and ductile; is also known as plastic cement, mastic, blackjack, roof tar, bull; Type II is generally has a high softening point and low ductility; is also known as vertical grade flashing cement

Asphalt Shingle

A paper felt or reinforced fiberglass mat coated with asphalt-coating with mineral granules embedded on the weather exposed side

ASTM International

Formerly known as American Society for Testing and Materials; develops and designates voluntary standards used worldwide to improve product quality, safety, and consumer confidence


Open space above the ceiling and immediately below the roof deck on steep-sloped roof systems

Back Nailing

Also known as blind nailing; the practice of driving nails or fasteners in the back portion of concealed roofing ply, steep roofing unit, or some other roofing component so that the fasteners are covered by the next ply and are not exposed to the weather; also used to prevent slippage in hot-mopping


Rock, aggregrate, or pavers placed on single-ply roofing membranes to hold in place

Base Coat

Initial coating in a series of coatings

Base Ply

First ply of roofing in a roof membrane or roof system

Base Sheet

Initial sheet or ply in multi-ply built up and modified bitumen roof membrane systems


A plastic, wood, or metal strip fastened as to hold up roof membranes up at walls or hold base flashing in place; strip of wood used to set in or over the deck; a cap or cover; a metal closure set over or covering the joint between metal panels


Typically horizontal beam on on a roof structure that holds the roof loads; there are three types: simple, continuous, and cantilever


Generic term for any material made of bitumen, typically asphalt and coal tar


Treated with or containing bitumen


A pocket of air trapped caused by water vapor or gases in between layers of membranes, between felt and membrane, or between the substrate and membrane


Wood built up around curbs, drains, and other penetrations that serve to support a curb, as a wood nailer for membrane attachment, or to strengthen the deck around an opening


When high winds rip shingles or part of a shingle off the roof


Two subjects held together by adhesive or cohesive forces

Bonding Agent

An adhesive applied to a substrate and next layer to create a bond


Flexible material, usually in a particular shape, used to seal a penetration; flexible material used to create a closure, typically on inside and outside corners, usually an issue for roof repair


Also known as a metal brake; a piece of equipment used to bend and form metal; can be hand or power-activated machinery


Use of a broom or squeegee to smooth a membrane ply to adhesive or bitumen under the membrane to insure proper contact


Tented displacement of roof membrane or shingles usually occurring over insulation or deck joints

Building Code

Published designations and ordinances by designated jurisdictions that prescribe design loads, the quality of material, construction details, procedures, building locations, maintenance, use, and occupancy in the area that the code has been adopted


Package of shingles or shakes


Built up roof membrane; a multi-ply roofing system where semi-flexible membrane or felts are applied with alternating layers of bitumen; typically the top layer is mineral aggregate and bitumen, liquid applied coating, or granulated cap sheet

Butt Edge

Lower edge of shingle, tile or shake

Butt Joint

When two adjacent and separate sections of material meet and form a joint

Butyl Tape

Sealant tape sometimes used at end laps and metal roof seams, some sheet metal joints, and other sealant applications


Overhanging roof structure over entrances and doors

Cant Strip

Triangular or beveled strip of wood, wood fiber, perlite, or other material that is used under flashing to modify the angle where the membrane meets a wall or curb

Cap Flashing

Typically metal piece used to cover the upper edges of base, wall, or primary flashing

Cap Sheet

Granulated sheet used as the top ply of built up roof membrane


Used in all areas of roofing, including roof installation, roof maintenance, and roof repairs for sealing a joint, juncture, seam, crack, or void with caulk to make them watertight

Chalk Line

Line made by snapping a string covered in colored chalk, a chalk box; used to align roof material during installation


When certain ingredients in coatings, paints, and other materials degrade or migrate out of the material


Stone or masonry structure that projects out of the roof that provides ventilation for smoke and flue gases


The horizontal or inclined member of a truss that resists bending


A strip, plate, or angled metal that serves to secure two or more components together, such as when coping metal attaches to the cleat

Closed Cut Valley

Shingle valley installation where shingles from one side completely cover the valley and are then trimmed back to match the valley lines


A layer of material applied by brush, roller, or spray used for waterproofing, further roof protection, and decoration


Degree of bonding a material has to itself

Cold Process

Roof membrane installed with alternating layers of cold applied roofing cement and a top layer of cold applied coating or cap sheet


Metal flashing used around vent pipes


Water vapor and other gases convert to liquid as the temperature lowers


A covering piece of a wall, sometimes secured with fasteners in the back and cleat under the front


Formed metal that protects and covers the upper edge of base flashing that is secured into a wall, curb, or pipe


A row of shingles or layer of roof material


Fracture in roof membrane


Network of fine cracks in roof membrane or coating


Elevated area on a roof to divert water around a chimney or curb, or away from a wall or expansion joint

Cross Ventilation

When air moves through a roof cavity between vents


Also known as crow’s nest; small roof structure that sets on the ridge or peak of the main roof


A curl in shingles or shakes


Process from heat, chemicals, pressure, or weatherization that causes material to form permanent molecular linkages


Open portion between the tabs of a three tab shingle

Dead Level

No slope; absolutely horizontal

Dead Loads

Rooftop loads, such as mechanical or HVAC equipment, that does not move


Structural surface or substrate that roof material is applied


Separation of the plies or laminated layers of a component or system

Dew Point

Temperature that water vapor begins to condensate


Half circle shaped roof


Raised projection that extends out of a sloped roof, many times for the purpose of placing a window


A conduit that drains water from scuppers, gutters, or conductor heads off the roof


Similar to a sink drain, it collects and directs water off the roof, sometimes the cause for a roof repair and must be maintained regularly

Drip Edge

Installed metal lip that keeps shingle edges off the roof deck and extends the shingles over eaves and gutters; metal flashing on the lower edge of a roof that controls the direction of dripping water

Dynamic Load

Wind or moving load on a roof


Projecting roof edge that extends past the outside wall


Process where granules are pressed onto shingles or coating, or where hot bitumen or adhesive is pressed onto felt, fabric, or mat

End Laps

When the end of rolled membrane is overlapped by the next sheet


Ethylene Propylene Diene Monomer; also known as rubber roofs; this system can be ballasted, mechanically attached, or fully adhered

Expansion Joint

Structural separation allowing free movement between two buildings to avoid roof system damage

Exposed Nail

Any nail left exposed to the environment without sealant or being covered


Part of roof system left exposed to the environment and weather


Small sized dormer, usually having an arched curved


Reinforcing inorganic or organic thread, filaments, or yarn used in certain membranes

Factory Mutual (FM Approvals)

Mutual company that researches and classifies roof systems on fire resistance and wind uplift resistance

Factory Seam

Seam or splice made by the manufacturer


A board or metal running horizontal under the roof edge


Any nail, staple, screw,cleat, bolt, clip, etc that is used to secure roofing material or components


Organic, fiberglass, asbestos, or polyester sheet used as a waterproofing layer under the primary roofing material


Metal sleeve around a gutter spike

Fiberglass Insulation

Insulation made of fiberglass, that can be blanket or rigid type; rigid insulation boards are used with flat and metal roofs


Main portion of the roof, not to include the perimeter or flashing areas


A half cylindrical opening or void in a lap edge or seam, or at the cut edge of a shingle

Flame Retardant

A substance added to reduce or retard material from burning


Rigid metal pan used around flashing pieces, such as skylight flange, flashing boot, chimneys, etc


System or material used to seal and waterproof around any roof penetration

Flashing Cement

Trowel grade Type II roof cement that may include organic or inorganic fibers that allow it to be used on vertical surfaces; also called vertical grade

Flashing Collar

Flashing used to seal pipes and other roof penetrations; also called roof jack or flashing boot

Flood Coat

Top layer of aggregate embedded bitumen on a built up roof

Flood Test

Also known as water test; practice where a controlled amount of water is used to test if a portion of a roof is watertight; sometimes used to find roof leaks


Traditional roof style; triangular portion under the sloping roof and above the eave line at the endwall of a building

Galvanized Steel

Steel coated with zinc to resist corrosion


Also called a barn style roof; a roof with two slopes on one side


Aggregate used to surface shingles, cap sheets, and other granule-surfaced roof material


Small rounded rock that eroded naturally and is used as aggregate

Gravel Stop

Metal flange at the roof edge that keeps aggregate from washing off the roof


Channeled trough or duct installed on the downslope perimeter of a roof to collect and divert rainwater away from the building

Hand Sealing

Method of sealing shingles on steep slopes, installing in cold weather, in high wind areas, and when shingle bonds have been broken, such as when doing a repair

Heat Welding

Method of melting and fusing overlapping seams together by heat and pressure


Metal folded back on itself to reinforce or create a safe edge

High Nailing

When a shingle is nailed above the manufacture’s specified nail location

Hip Legs

The down slope ridges on hip roofs

Hip Roof

Roof with no vertical ends, that rises by inclined planes coming together at a peak and four separate hip legs


Term for hot bitumen


Heating, venting, and air conditioning equipment

Ice Dam

Mass of ice or snow that melts and re-freezes at eave areas, forcing water and ice to back up under the roofing material

Impact Resistance

Ability of roofing material to resist impacts, such as puncturing from falling objects and foot traffic


To saturate or coat with a liquid material, such as bitumen or coating


Slope of a roof expressed by the number of vertical units of rise per horizontal units of run

Infrared Thermography

Method to locate wet or moist insulation by infrared camera

Interlocking Shingles

Individually separate shingles that are mechanically attached to each to provide wind resistance


Wooden or metal beams arranged in a parallel fashion from wall to wall to support a roof, ceiling, or floor of a building


Imperfection in fabric construction that causes surface irregularities

Laminated Shingles

Also known as dimensional shingles and architectural shingles; shingles made from two separate pieces and are then laminated together


The part of roofing component that overlaps the same or another component

Lap Cement

Roof cement made to adhere to overlapping membranes or asphalt roll roofing

Lap Seam

Seamed, sealed, or bonded overlapping materials


Soft metal used for certain flashing

Live Loads

Temporary loads, such as snow, rain, wind, people, installation equipment, etc, that the roof must be designed to support

Loose Laid

Membrane that is not attached to the substrateexcept at the perimeter and penetrations, but is held down by ballast


A nearly vertical decorative roof on the perimeter of a building


Flashing cement or asphalt mastic


General term for certain rolled material and base material of shingles


When roofing membrane is attached to a substrate by fasteners, with plates or batten


Flexible or semi-flexible roofing material used in low slope and flat roofs to watertight the roof; examples are TPO, PVC, modified bitumen, EPDM

Metal Flashing

See flashing; flashing typically made from sheet metal for coping, step flashing, counterflashing, riglet metal, etc.


One mil is equal to 0.001 inches; used to indicate how thick a roof membrane is


Mold in early stage; fungal growth caused in damp conditions

Mineral Granules

See granules; aggregate used to surface shingles, cap sheets, and other roof materials

Mineral-Surfaced Sheet

Roofing sheet that is surfaced with mineral granules, either on one side or both


Joint made by joining two diagonally cut pieces of wood so they produce a 90 degree angle

Modified Bitumen

Rolled bitumen roofing membrane with one or more polymer included, such as atactic polypropylene (APP), that can be torched down or applied by cold process, or stryene butadiene stryene (SBS), which can be heat welded or applied by cold process


Method of applying hot bitumen, with either a mechanical applicator or by a hand mop


A mixture of sand, limestone, mortar, and water that holds bricks together

Nail Guide Line

A painted line on laminated shingles to aid the installer in drive nails in the proper placement

Nail Pop

When a nail is not driven in fully, or backs out off the deck due to building movement, and sits above the roof deck; these nails can sometimes pop through the roof material or shingle and cause a roof leak


Synthetic rubber, that can be made into rolls for flashing, cement, or coating to watertight


Used when installing a second shingle layer to cover 3 tab shingles with larger shingles, such as architectural shingles, so to avoid the underlaying shingles cupping

Night Tie-In (Night Seal, Night Tie-Off)

Method of temporarily sealing a roof membrane to protect from water intrusion until the installer can come back, usually the next day, to finish the roof


National Roofing Contractors Association

Open Valley

Method valley installation on a shingle roof where metal is used down the valley center


Any material made from plant or animal matter

Organic Felt

An organic base material saturated with asphalt and used as underlayment between the substrate and shingles or roofing material

Organic Mat

Mat made from recycled wood pulp and paper

Organic Shingles

Shingles made with an organic base mat


Orientated Strand Board; made from wood chips and lamination glues and used as roof decking


Occupational Safety and Health Administration; government administration that sets rules and regulations to provide safe working conditions


When fasteners are driven too far that the roofing material rips or is punctured


When shingles or shingle courses are placed higher than their intended exposure; may cause shingles to blow off or roof leaks


Flat bottom part between the ribs of a roofing panel

Parapet Wall

Any part of a perimeter wall that is entirely above the roof


Any object, such a pipe, vent, electrical conduit, etc, that passes through the roof


Light weight, insulating aggregate used in concrete insulation and preformed perlitic insulation board

Phased Application/Installation

Installation of a roof system during two or more separate time intervals

Pitch Pocket

A form of flashing around a penetration that is filled with bituminous or polymeric sealants to help reduce the risk of roof leaks

Plastic Cement

Type I trowel grade roof cement used for low slope applications


The physical property of material being flexible or bendable


A layer of roof material, such as felt, ply sheet, or membrane, in a roof system


Water that is sitting on a roof and has not drained off completely

Positive Drainage

A flat roof having sufficient slope to ensure drainage of water off the roof within 48 hours


Liquid applied solution used to improve the adhesion and increase the strength between two surfaces bonded together

Puncture Resistance

The extent of a roofing material to be able to withstand the action of sharp objects without becoming perforated


Secondary horizontal structural member that supports the rafters of the roof by transferring the load from the primary framing

Quarter Sized

Term for the size of the dabs in hand sealing shingles during roof repairs, extreme steep slope, and high winds; based on the size of a U.S. quarter


Unrecommended method of installing shingles straight up the roof


One of a series of sloped beams that supports a sloped roof and its loads


A thin cut in a masonry wall used to insert a flashing component, such as a reglet


Sloped edge of a gable style roof plane

Rake Starter

Starter strip, bleeder strip; first course of shingles installed along the rake edges that is trimmed


Covering an existing roof system with a new one without tearing the original one off


Metal receiver between a wall and roof used for attachment of counterflashing

Reinforced Membrane

Membrane that has been strengthened with one or more reinforcing material

Relative Humidity

Ratio of the weight of moisture in a given volume of air

Release Film

Plastic strip installed on the back of shingles used to keep the shingles from sticking to each other during shipping and installation


Removing the existing roof system to replace it with a new one


Highest outer horizontal point that two sloped roofs meet

Ridge Cap

Roof material used to cover a roof ridge

Ridge Cap Shingles

Shingles specifically manufactured to install on the ridge of a shingle roof

Ridge Course

The last or top row course of shingles, tiles, slate, shake, or other roofing material that covers the ridge

Ridge Vent

Vent located on the roof ridge that allows warm and moist air out of the attic; most are prefabricated shingle over types; typically the ridge needs to be cut during installation to allow for an opening for the air to escape

Roof Assembly

Roof components assembled together to make a complete roof system

Roof Jack

Metal bracket nailed under shingles, shake, etc. used to support toe boards on steep roofs

Roof Louvers

Also know as airhawks, box vents, mushroom vents, soldier vents; rectangular shaped roof vents

Roof Plane

Roof area having four separate edges

Roof Repair

Act of fixing roof damage or a roof leak

Roof Slope

Angle of a roof, expressed by the ratio of units of vertical rise to horizontal length


Horizontal component of slope


Small, raised structure composed similar to a hip roof or pyramid constructed to divert water; may be located between drains, valleys, or behind a chimney


Area of roof is lower than the rest of the roof due to damaged decking or building movement

Saturated Felt

Felt that has been saturated with bitumen


Exposed section of double thickness on certain shingles used to imitate a wood shake look

Scupper Box

Also known as conductor heads, collector heads, leader heads; component used in roof drainage to collect rainwater and channel it through a downspout


A hatch that provides access from the inside of a building to the roof


Watertight a roof component or roof system


A mixture of polymers, fibers, fillers, and pigments used to fill and seal joints that cures to a solid

Seam Strength

The force required to separate a roof membrane seam

Self-Adhering Membrane

Also known as peel and stick; a membrane that can adhere to a substrate without additional adhesives

Self-Drilling Screw

Fastener that allow drilling and fastening to be done at the same time in one application

Self-Sealing Shingle

Factory-applied adhesive installed on the back of a shingle with the purpose of bonding to the overlaying shingle once heat has activated the sealant


Edge that is different from the rest of the material to resist fraying or for overlapping seams

Selvage Joint

Overlapping seam typically in granule surfaced cap sheets where the edges are not granulated


Slight difference in color of roof materials, such as shingle colors

Shed Roof

A roof with only one roof plane that does not tie into any other roofs


Individual roof covering that is installed in courses with the above courses overlapping the shingles below; to apply shingles to a roof


Installation of shingles to a roof

Side Lap

Where one roll overlaps the roll beneath it in a continuous longitudinal fashion

Side Walls

Vertical roof plane meets a vertical wall


Framed horizontal bottom of an opening, such as a window


A roof accessory mounted on a rooftop curb designed to admit light


Hard metamorphic rock used as dimensional stone for sloped roofs


Movement of roof membranes on a slope that exposes the lower plies or even base sheet


Angle of incline, expressed by the number of vertical units of rise per horizontal units of run

Snow Guard

A series of devices installed on a roof to hold snow to prevent snow or ice slides from sliding off the roof

Snow Load

A live or environmental load; load on buildings caused by snowfall


Underside of the exterior overhanging of a building

Soffit Vent

Air inlet source located under the eaves, roof edge, or soffitt

Soil Stack

Sanitation pipe that penetrates the roof


When the outer layer of masonry or bricks begin to break or flake away

Splash Block

Small block laid on the ground under a downspout to avoid soil erosion


Tear in roof material from substrate or material stress


Act of removing roof aggregate, particularly build up roofs, by scraping and chipping


100 square feet of a roof area

Stack Vent

Vertical outlet designed to relieve the moisture vapor pressure from between the substrate and roof membrane

Stainless Steel

Chromium, nickel, or copper added to steel for the purpose of resisting corrosion

Standing Seam

Overlapping or interlocking seam at an upturned rib on a metal roof

Starter Sheet

Felt or membrane used at the perimeters of a roof area on mechanically attached roof systems or at the edge of the roof on shingle roofs

Starter Strip

First course of roofing installed; roll roofing or shingle strips applies at the eave line to fill gaps between cutouts and joints

Static Load

Any load on a roof that does not change position or size over time

Step Flashing

Individual pieces of metal overlapping each other used to flash walls, chimneys, and dormers


Structural deck or insulation that roofing membrane is applied


Depression made around a roof drain or scupper box to aid in drainage

Superimposed Load

Loads that are added to existing loads


Bottom exposed portion of strip shingles separated by cutouts

Tapered Insulation

Insulation providing a gradual transition from one level to another with the purpose of installing crickets or building the roof up around curbs

Tear Off

Removal of the existing roof down to the deck

Test Cut

Taking a sample of a roof to diagnose the condition of the membrane or the materials on the existing roof system

Thermal Resistance

Resistance that a material has to heat flow

Thermal Shock

Stress applied to roofing material from sudden temperature change

Through Wall Flashing

Roofing membrane or material that extends through a wall to direct water away from the wall

Tie Off

To form a waterproof seal at a termination or flashing; act of using rope or other device attached to a secure point on a roof and the other end attached to a harness worn by the roofer to protect them from falling

Tongue and Groove

Type of joint made by one piece having a cut groove and the other an outward tongue; used so adjacent planks fit in alignment to form a uniform deck


When a roof plane meets another roof plane with different slopes


Underwriters Laboratory; non-profit organization that tests, inspects, and classifies products for safety and efficiency

Ultraviolet (UV)

Form of radiation invisible to the human eye, situated just past the violet end of the visible spectrum; over time, ultraviolet radiation can cause roof material to age and degrade


When a fastener is not fully driven flush; if not corrected, underdriven fasteners can pop through the roof material and cause roof leaks


Sheet installed over the roof substrate and under the roof system, typically in steep slope roofs; used to provide a secondary layer of weather protection


V shaped depression on a roof caused from the intersection of two sloping roof planes


Moisture laden air

Vapor Migration

Movement of water vapor from an area of a higher amount of water vapor pressure to an area of a lower amount of water vapor pressure

Vapor Retarder

Material installed to restrict or impede water vapor moving through a roof or wall assembly


An opening designed to allow for the passage of air and water vapor from inside a building to the outside


A naturally occurring mineral used in attic and concrete insulation


Written promise to the building owner concerning the roof system and roof materials

Water Cutoff

Extremely tacky compound used to seal and waterproof with compression type terminations

Waterproof Underlayments

Modified bitumen based underlayments used to seal wood decks and waterproof critical areas, such as eaves and valleys


Treatment of material, a surface, or a structure to prevent the intrusion of water

Weep Holes

Small opening to allow the drainage of water from a building component, such as a skylight or brick wall


Moisture moved by capillary action

Wind Uplift

Force caused when wind pressure is greater below a roof than above the roof; if this force is greater than the roof is designed for, the roof could be lifted off the building

Woven Valley

Method of valley construction where shingles extend acroos the valley and each alternate course overlaps the other

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