Roofing Glossary & Terminology

A

Abrasion resistance is the ability to withstand wear and tear caused by contact with rough surfaces like foot traffic, machinery, wind-blown particles, and tree limbs.

Absorption is when a material can soak up stuff like gases or liquids, like water. It’s like the material is a sponge!

Accelerated weathering is a process where a specimen is exposed to a specific test environment for a certain period of time in order to simulate the effects of natural weathering in a shorter time frame.

Acrylic resin is a type of polymer made from acrylic or methacrylic monomers. It is commonly used as a latex base for coating systems.

Adhesion refers to the attachment between two surfaces, which can be achieved through mechanical or chemical forces. It can also refer to the bonding between layers of the same substance. The strength of adhesion is determined by the molecular forces and mechanical interlocking between the adhesive and the bonded surface. Adhesion is measured in shear and peel modes.

Adhesive is a substance that creates a strong and steady bond between two surfaces.

Aged R-Value is a thermal resistance value determined through artificial conditioning for a specific duration.

Aging refers to the impact of being exposed to an environment over time, or the process of subjecting materials to an environment for a certain duration.

American Institute of Architects (AIA) is a professional organization that represents architects in the United States. They provide resources and support for architects, promote the value of architecture, and advocate for the profession.

Air barrier is a construction material that helps control the flow of air in and out of a building. It prevents uncontrolled air leakage.

Air infiltration is the unintentional entry of outside air into a building, which can lead to energy loss and discomfort.

Air leakage is when air escapes from where it’s supposed to stay, and goes where it’s not supposed to go.

American National Standards Institute (ANSI) develops and promotes standards for various industries in the United States.

Application rate refers to the amount of material applied per unit area, whether it’s measured by mass, volume, or thickness.

Architect is a licensed professional who designs and oversees the construction of buildings.

Area divider is a raised assembly that separates large roof areas or systems made of different materials. It is attached to a wood base plate and anchored to the roof deck. It can also help with installing tapered insulation.

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is a professional organization that focuses on heating, refrigeration, and air conditioning engineering.

Asphalt is a dark brown to black substance made from bitumen found in natural sources or leftover from processing crude oil. It can be refined for different roofing purposes, such as dead-level, flat, steep, special steep, and waterproofing.

Asphalt felt is a type of felt that is saturated and/or coated with asphalt.

American Society for Testing and Materials (ASTM) International is the largest voluntary standards development organization globally.

B

Ballast is a material used to hold a roof membrane system in place. It can be made of various materials such as smooth river stone, crushed stone, or concrete pavers. The ballast relies on its weight and gravity to keep the roof in position.

Base flashing is strips of roof membrane material used to seal the intersection between the roof and a vertical surface, like a wall. It covers the edge of the main roof material and extends up the wall.

Base ply is the first layer in a roof system that allows for more layers to be added later.

Base sheet is a felt that is used as the first layer in certain low-slope roof systems. It can be impregnated, saturated, or coated.

Bitumen is a black, sticky substance made of hydrocarbons that can be found in asphalt, tar, and coal tar. It is used in construction and can be dissolved in carbon disulfide.

Bituminous refers to materials that are made with or treated with bitumen, such as bituminous concrete, felts, fabrics, and pavement.

Bituminous waterproofing is a method of waterproofing that can only be used on the positive side. It involves applying cold or hot bituminous material with reinforcement.

Blanket insulation is a type of compressible fibrous insulation, usually found in roll form.

Blister is a raised portion on a roofing membrane caused by trapped air or water between layers, or by separation of a coating from the substrate.

Blowing agent is a substance that creates gas through chemical or thermal action, used in making hollow or cellular materials.

Bond refers to the forces holding two components together, a type of surety, or a guarantee for roof system performance.

Bracing structural elements are installed to provide support and stability to other members in order to create a stable structure. They can include knee braces, cables, rods, struts, ties, shores, diaphragms, and rigid frames, among others.

British thermal unit (Btu) is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit.

Buckle is when the roof membrane moves upward and stretches over insulation or deck joints. It can mean that there is movement happening within the roof structure.

Building codes are rules that dictate how buildings should be designed, constructed, and maintained. They are set by national organizations and adopted by local authorities. These codes cover everything from materials to use and occupancy.

Building envelope refers to the exterior of a building.

Built-up roof (BUR) is a flexible roofing system made up of layers of felt, fabrics, and bitumen that are assembled on-site. It is topped with materials like mineral aggregate or liquid coatings.

Butt edge is the lower, exposed edge of a shingle, tile, or shake.

Butt joint is two separate sections of material are joined together, like when two pieces of insulation meet.

C

Cant strip is a beveled strip used to change the angle where the roof or waterproofing membrane meets a vertical element.

Cap flashing is a metal covering that protects the upper edges of membrane base flashing or wall flashing. It is also used to cover the top of different building components like parapets or columns.

Cap sheet is a granule-surfaced sheet used as the top layer in certain types of roof membranes and flashings.

Capillary action is when a liquid is either raised or lowered on a solid surface due to the attraction between the liquid molecules and the solid. It can also refer to the process of liquid being drawn into a gap between two surfaces.

Cellular concrete is a roof deck material made of cement, water, foam, and air, with a density of 24 to 32 pounds per cubic foot when dry.

Centimeter is a metric unit that is equal to 0.01 meters or 0.393 inches.

Centipoise (cP) is a unit of measure for viscosity in the centimeter-gram-second system, where 1 cP is equal to one one-hundredth of a poise. Water at 70 F has a viscosity of one centipoise. The lower the number, the less viscous the material.

Centistokes (cSt) is a unit of kinematic viscosity in the centimeter-gram-second system, equal to one one-hundredth of a stokes. It is used to measure the ratio of a liquid’s dynamic viscosity to its density.

Chemical resistance refers to the ability of a material to maintain its properties when it comes into contact with certain chemicals.

Cladding is the material that covers the outside walls of a building.

Coated felt is an asphalt or fiberglass material that has been coated on both sides with a harder, more viscous asphalt.

Coating is a fluid material that is applied to a roof surface to protect it from the weather. It acts as a film over the original roof substrate.

Code is a set of laws created by a governing body to regulate certain activities.

Cold-applied materials can be used without heating, while hot-applied materials need to be heated before use. Cold-applied materials are liquid, while hot-applied materials are solid and need to be liquefied before use.

Combustible pertains to something that can catch fire and burn.

Commercial Roofing is a special roofing trade that focuses on large industrial commercial buildings using polyurethane foam, TPO, rubber, modified bitumen, and metal roofing products.

Compressive strength is a material’s ability to withstand compression loads.

Condensation is when water vapor or gas turns into liquid due to temperature decrease or pressure increase. It’s the act of condensing.

Control joint is a groove in concrete or masonry that helps prevent cracking and separation caused by dimensional changes in the structure. It helps avoid high stress and ensures the structure remains intact.

Cool roofs are made of reflective materials that keep the surface cooler than regular roofs when exposed to sunlight. They are a great choice for reducing heat in buildings.

Course is a row of roofing material that forms a waterproofing or flashing system. It can also refer to a layer of materials applied to a surface, such as a wall flashing composed of roof cement and felt or fabric.

Coverage refers to how much surface area is covered by a certain amount of material at a specific thickness.

Cover boards are used to prevent blistering when hot bituminous membranes are used with closed cell plastic foam insulation. Suitable cover boards include glass-faced siliconized gypsum board, fiberglass board, perlite board, wood fiberboard, or mineral fiberboard. They are also recommended to protect polyisocyanurate insulation when used with single-ply membranes.

Crack is a break or separation in a material.

Coatings can develop cracks that go all the way through the surface and reach the underlying layers.

Cricket is a small roof area that helps divert water from the intersection of a roof with a chimney, wall, or other projection. It prevents water from pooling and causing damage.

Curb is a raised structure used to support roof penetrations like skylights and mechanical equipment above the roof surface. It can also refer to a low-height raised perimeter around the roof.

Cure is when a material forms permanent molecular linkages through exposure to chemicals, heat, pressure, or weathering.

Cure time refers to the duration it takes for a material to achieve its desired long-term physical properties.

Cutback is a solvent-thinned bitumen in various roofing materials like adhesives, cements, and coatings.

D

Damp-proofing treatment prevents water from passing through surfaces or structures without pressure.

Dead load refers to the weight of a structure and any fixtures or equipment attached to it.

Deck is a part of a building’s roof that needs to be strong enough to support the weight of the roof and other loads. It also provides a base for the roof or waterproofing system. Decks can be made of noncombustible materials like metal or concrete, or combustible materials like wood.

Deflection is the bending or sagging of a structural member due to applied loads, or any displacement of a body from its original position caused by external forces.

Deformation is when a body changes shape or dimensions due to stress or force, without breaking apart.

Delamination is when the layers of a component or system separate.

Dew point temperature is when the air is completely filled with water vapor and has a relative humidity of 100 percent.

Diffusion is the movement of water vapor or other substances from areas of high concentration to areas of lower concentration, making the composition more uniform. It can happen in gases, liquids, or solids, and involves the spontaneous movement of atoms or molecules within a material.

Dimensional stability refers to how well a material keeps its size and shape when exposed to different temperatures and humidity levels.

Downspout is a vertical pipe that carries water from a building’s roof to the ground or storm water system. It is also known as a conductor or leader.

Drainage course is a layer in a roof system that allows moisture to move sideways and relieves pressure caused by water.

Drip edge is a metal flashing that hangs over the edge of a building to control dripping water and protect the structure.

Drying time refers to the amount of time it takes for a material to dry completely and not be affected by things like rain or freezing weather.

Durability is something that has the ability to survive physical, chemical, and environmental abuse.

Dynamic load refers to any load that is not stationary, such as wind or moving live loads.

E

Efflorescence is a white deposit that forms on surfaces like stone, brick, plaster, or mortar. It is caused by alkalies leaching from nearby concrete or mortar as moisture passes through.

Elongation is the measure of how much a material stretches compared to its original length, typically expressed as a percentage.

Embedment is the process of pressing or positioning materials into hot bitumen or adhesive to ensure contact, or pressing granules into coating in the manufacture of roofing.

Emissivity is a measure of how well a surface can release heat through infrared radiation. It is expressed as a percentage or decimal factor and is compared to the emission of a black body at the same temperature.

End lap refers to the distance where one layer extends beyond the adjacent layer.

Ethylene, Propylene and Diene (EPDM) is a type of synthetic rubber. It can be vulcanized and is known for its thermosetting properties. EPDM is short for “ethylene propylene diene M-class rubber” and is also referred to as ethylene propylene diene terpolymer.

Equiviscous temperature (EVT) is the temperature at which bitumen becomes the right consistency for applying built-up membranes.

Equiviscous temperature application range for applying bitumen is approximately 25 degrees Fahrenheit above or below the Equiviscous temperature (EVT), giving a range of about 50 degrees Fahrenheit. The EVT is measured in the mop cart or mechanical spreader right before applying the bitumen to the substrate.

Expanded polystyrene (EPS) is a plastic foam insulation product made from expanded polystyrene beads. It has a closed-cell structure and is manufactured through a molding process to create boards or blocks.

Expansion joint is a way to separate two parts of a building so they can move independently without causing damage to the roof or waterproofing system.

Exterior insulation and finish system (EIFS) is an outdoor wall finish system that includes insulation, attachments, reinforcement, and a compatible finish.

Extruded polystyrene (XPS) is a plastic foam insulation made by foaming resin through a continuous extrusion process, resulting in a tightly sealed board.

F

Facer is the outer layer of an insulation board, made of a different material than the insulation itself. It can be paper, glass mat, or a combination, coated with asphalt, latex, or metal foil.

Fasteners are mechanical devices like nails, screws, and bolts that are used to secure different parts of a roof.

Felt is a versatile material made by combining fibers with a binder or through mechanical work, moisture, and heat. It can be made from various materials like wood pulp, vegetable fibers, asbestos, glass fibers, or polyester fibers.

Fiberglass base sheet that is used in the construction of built-up roof systems. It is reinforced with fiberglass, coated with asphalt, and topped with mineral matter.

Fireproofing materials are used to prevent the spread of fire.

Fire resistance is the ability of materials or their combinations to prevent or slow down the spread of intense heat, hot gases, or flames when in use.

Fishmouth is a term used to describe a half-cylindrical or half-conical opening or void that can occur in the lapped edge or seam of a material, such as ply sheets or shingles. This can be caused by wrinkling or shifting during installation, resulting in an edge wrinkle. In shingles, fishmouth refers to a half-conical opening that forms at a cut edge.

Flame spread is when a flame moves away from where it started.

Flash point is the lowest temperature at which a substance can catch fire when exposed to a spark or flame.

Flashing components are used to seal and protect roof system edges, penetrations, and other areas where the roof covering is interrupted. This includes base flashing for the edge of the membrane and cap flashings for the upper edges.

Flood coat is a layer of bitumen that is used on a built-up roof to embed surfacing aggregate.

FM Approvals, also known as FM, is a research and testing unit of FM Global that assesses the fire, traffic, impact, weathering, and wind resistance of roofing components and assemblies.

G

Gauge measures metal thickness, with a lower number indicating a thicker metal.

Granules are colored aggregate used on roofs, also known as mineral or ceramic granules.

Gypsum board panels are commonly used in roofs as a barrier, thermal barrier, or cover board. They have a noncombustible core primarily made of gypsum.

H

Header is a horizontal framing member used in doors, windows, or other openings. It provides structural support.

Heat-fused sheet is installed by heating the sheet underside with a propane torch, melting the bitumen and sticking the sheet in the melted material.

Heat transfer is the movement of heat from a hot place to a cooler place, and it can happen through conduction, convection, or radiation.

Heat welding is a process of melting and joining separate sheets of roofing materials using heat and pressure.

HVAC is the acronym for heating, ventilating, and air-conditioning equipment. It is used to control the temperature, humidity, and air quality in buildings.

Hydrostatic pressure is the pressure exerted on a surface by a column of water of a certain height.

I

Ice dam is a big chunk of ice that forms on the edge of a roof when melted snow refreezes. This can cause water to back up and leak into the house.

Impregnating means fully covering the fibers in a felt or mat with bitumen, filling the spaces between the fibers without a continuous bitumen coating on the surface.

Inorganic means anything made of non-hydrocarbon materials and are not derived from plants or animals.

In-Service R-Value is the thermal resistance value of a material measured during its expected service life under installed conditions.

Insulation is a material used to control heat flow in buildings.

J

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K

K-Value is a measure of thermal conductivity, representing the heat flow through a material per unit area, caused by a temperature difference. It is expressed in Btu•in/hr•ft2•F and measures the amount of heat passing through a 1-inch thickness of material in one hour with a 1-degree Fahrenheit temperature difference.

L

Laminate is the process of fusing or adhering layers of materials together.

Lap is when one part of a roofing, waterproofing, or flashing component covers another adjacent component.

Lap seam is when materials overlap and are bonded together.

Life-cycle assessment (LCA) is a way to evaluate the environmental impact of a product or system throughout its entire life. It considers all stages, from raw material extraction to disposal, and assesses factors such as energy consumption, pollution, and waste. LCA is an environmental review method.

Life-cycle cost analysis is a method of evaluating the total costs of a product or system throughout its entire lifespan, including raw materials, transportation, installation, maintenance, and disposal. It takes into account the costs of materials, energy consumption, and environmental impact at each stage.

Lightweight concrete is a type of concrete that has a lower density than regular concrete, and it is made with a combination of materials such as gypsum, vermiculite, perlite, wood fibers, and air-entrained concrete.

Lightweight or insulating concrete fill (LWIC) is a lightweight concrete that can be made with or without aggregate additions. It consists of Portland cement, water, and air, and when dried, it has a unit weight of 50 lb/ft3 or less.

Liquid applied pertains to resins, bituminous cements, adhesives, or coatings by simply pouring them at room temperature or slightly warmer.

Liquid-applied built-up roof is a flexible roof membrane made of layers of felts, mats, or fabrics bonded together with roof cements and coated with a liquid sealant, sometimes with added aggregate.

Live loads pertains to how the roof structure must be able to support temporary loads like people, equipment, snow, ice, rain, as required by building codes. These loads are usually moving or dynamic.

Lot refers to all the material produced in one eight-hour shift of the same type and color. A delivery lot, on the other hand, includes all the material of the same type that is delivered at one time by one truck or railroad car.

Low-slope roofs are weatherproof membrane types of roof systems installed on slopes at or less than 3:12.

Low-temperature flexibility refers to its ability to avoid cracking when flexed after being cooled.

M

Masonry construction involves using natural or manufactured materials like stone, brick, concrete block, adobe, glass block, tile, manufactured stone, or gypsum block, set in mortar.

Mastic is a sticky substance that is used to hold waterproofing membrane in place.

Mat is a thin layer of fabric that strengthens a material or membrane.

Material Safety Data Sheet (MSDS) is a document that provides information about the chemicals in a material or product, as well as safe handling and emergency procedures. Manufacturers must create MSDSs, and employers must share the information with employees, as required by OSHA regulations.

Mechanical damage to a roof system refers to physical harm that is not a result of regular wear and tear. It can occur due to various factors and requires repair or replacement.

Mechanically fastened membrane is a type of membrane that is attached to a surface at specific points.

Membrane is a flexible or semiflexible roof covering that keeps water out.

Mil is a unit of measurement equal to 0.001 inches, commonly used to describe the thickness of a roof membrane.

Mineral fiber insulation is made from rock, slag, or glass fibers, with or without binders.

Mopping is the process of applying hot bitumen to a bituminous membrane using a mop or mechanical applicator. There are two types of mopping: solid mopping, which provides a continuous coating, and spot mopping, which leaves unmopped areas in a grid pattern.

N

Newton (N) Based on the name of Sir Issac Netwon, N is the SI unit of measure for force.

National Fire Protection Association (NFPA) is a nonprofit organization that aims to reduce the impact of fire and other hazards on people’s lives. They provide codes and standards, conduct research, and offer training and education. One of their publications is the NFPA 70, also known as the National Electrical Code.

National Institute of Standards and Technology (NIST) is a government agency that sets standards and promotes innovation in technology.

Nonwoven fabric is created by bonding or interlocking fibers through various methods like mechanical, chemical, thermal, or solvent means. It’s a textile structure that doesn’t require weaving or knitting.

National Roofing Contractors Association (NRCA) is a national organization for roofing contractors.

O

Organic means anything made up of hydrocarbons or substances derived from them, and can be of plant or animal origin.

Organic felt is a type of roofing material made from cellulose fibers.

Overburden refers to any material placed on top of a waterproofing system.

Overspray is when unwanted spray particles settle in the air. It’s pretty annoying.

Oxidation is a weathering process caused by various factors, including temperature and radiation. It can also refer to the loss of electrons in a chemical reaction, often involving oxygen.

P

Parapet wall is the part of a wall that sticks out above a roof.

Pedestal is a support for rooftop components like pavers, pipes, and small units. It provides a stable base.

Peel strength is the force needed to separate a flexible material from a rigid or another flexible material.

Penetration refers to any construction passing through a roof, such as pipes or HVAC supports. It can also describe the consistency of a bituminous material, measured by how far a needle or cone can penetrate into the material under specific conditions.

Perforated felt is a type of roofing material that has small holes to let air and moisture escape. It is classified based on ASTM requirements.

Permeability is the measure of how easily vapor or fluid can pass through a material, typically measured in units of grains per square inch per hour per foot of thickness. It is commonly used to describe the ability of a material to allow water vapor to pass through it.

Permeance is the measurement of water vapor transmission through a material, influenced by vapor pressure difference, temperature, and humidity. It is commonly measured in “perm” units.

Phased application refers to the installation of a roof or waterproofing system over multiple time intervals or different days. It is not considered phased application if surfacings are applied at different time intervals.

Pliability is the quality of being flexible or moldable.

Ply is an added layer of felt or ply sheet to a built-up roof membrane or system.

Polyester is a type of polymer made up of ester units in its chain.

Polyisocyanurate foam board, also known as iso or isoboard, is a thermal insulation made of polyisocyanurate foam with facers attached. It is classified according to ASTM C1289.

Polymer A is a cool material made by combining different chemicals.

Polymer-modified bitumen is a type of bitumen that is enhanced with polymers, such as atactic polypropylene and styrene butadiene styrene. It is commonly used in composite sheets that are reinforced with mats or films and can be surfaced with films, foils, or mineral granules.

Polyvinyl Chloride (PVC) is a synthetic polymer made from vinyl chloride. It can be made into flexible or rigid forms using additives. Rigid PVC is used for pipes, while flexible PVC is used for sheeting and roof membranes.

Polystyrene is a polymer made by combining styrene, and it’s pretty cool.

Ponding is when water accumulates on a roof for more than 48 hours after it rains and doesn’t dry up easily.

Positive draining pertains to a roof that has been designed to ensure that water drains within 48 hours of rain, with the deck and roof slope taken into account.

Pressure-sensitive adhesives are tacky at room temperature and stick to different surfaces when pressure is applied, without needing heat or other energy sources.

Prestressed concrete is a type of concrete that is reinforced with tensioned cables, wires, or rods before any load is applied to the structure. This technique helps to keep the concrete under compression, resulting in increased strength.

Protected membrane roof is a type of roof assembly where the insulation and ballast are placed on top of the membrane. It is sometimes called an inverted roof assembly.

Protection course is a sacrificial material or separate layer installed to shield a waterproofing material or vegetative roof membrane from external damage.

Pounds Per Square Inch (PSI), is a unit of pressure commonly used to measure the force exerted on a given area, aka pressure measurement.

Puncture resistance is a material’s ability to withstand objects that penetrate or puncture it.

Purlin is a horizontal beam that helps support the main structural frame.

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R

Re-covering is the process of adding a new roof covering on top of an existing one without removing the old one.

Reflectance is the measure of how much solar energy is reflected by a surface, expressed as a percentage or decimal value between 0.00 and 1.00.

Reflectivity refers to the amount of light that is reflected by a surface or coating. It is a property of the material itself, while “reflectance” refers to the amount of light reflected by a sample of the material.

Reinforced membrane is a roof or waterproofing membrane that has been made stronger by adding materials like glass fibers, polyester mats, or nylon sheets.

Relative humidity is the percentage of water vapor in the air compared to the maximum amount it can hold at that temperature.

Replacing a roof involves removing the old roof, fixing any damaged areas, and installing a new one; also called “tear-off and replacement.”

Reroofing is the process of replacing or recovering an existing roof covering.

Residential Roofing is a trade in the roofing industry that focuses on small to medium size buildings depending on property size. Residential roofing utilizes asphalt shingle, tile, underlayment, modified bitumen

Roll materials are roofing materials that come in rolls and include roofing felt and ply sheet.

Roll roofing is a type of roofing material that comes in smooth or mineral-surfaced options.

Roof is the top covering of a building, and to roof means to cover a building with a roof.

Roof assembly is a combination of different components like the roof deck, vapor retarder, insulation, and membrane or primary roof covering. Its purpose is to protect against weather conditions and make the roof waterproof.

Roof slope is the angle at which a roof surface is slanted. It is measured as a ratio of the vertical rise to the horizontal length or as an angle in degrees.

Roof system is a collection of components that work together to protect a building from the weather and improve its insulation. It includes a membrane or primary covering, insulation, and does not include the roof deck.

S

Saturant A is a type of bitumen that has a low softening point. It is used to soak dry felts in the production of saturated roofing felts.

Saturated felt is a porous material that has been soaked in hot bitumen, absorbing as much as it can while still containing voids.

Scrim is a fabric made of continuous strands used to reinforce membranes.

Seam is a joint made by joining two separate sections of material using various methods like adhesive bonding, welding, or using tape and sealant.

Self-adhering membrane is a type of material that can stick to a surface and to itself without needing any extra glue. It is usually protected by a release paper or film to avoid sticking together during transportation.

Self-adhesive materials stick to different surfaces when pressure is applied, without the need for additional substances to create the bond.

Selvage is an edge or edging on fabric or other materials that differs from the main part and serves a special purpose, such as overlapping or seaming.

Service life of a building component or system is the amount of time it will function properly without needing to be replaced or repaired, as long as regular maintenance is done. It can also refer to the number of years a material, system, or structure will last before needing to be rehabilitated or replaced.

Shear strength is the ability of two parts of a body to resist sliding in parallel to each other.

Shelf life is the maximum time you can store something before it becomes unusable. It depends on how you store it and what the manufacturer recommends.

Shingle Roof Installation is the process of removing the old roof, repairing sheathing and trim and laying down new underlayment and IKO traditional, performance or architectural shingles.

Shrinkage is when an object or material gets smaller in size.

Side lap is when similar materials overlap each other in a continuous longitudinal manner.

Side-lap fastener is a way to connect panels together at the side lap.

Slab is a flat layer of concrete that sits on the ground or is supported by beams, columns, or walls. It’s typically uniform in thickness and can be either horizontal or slightly sloped.

Slab below grade is a type of foundation that is placed below the ground level. It is commonly referred to as a “slab on grade.”

Slab on grade is when concrete is poured directly over the ground.

Slope is the angle of incline, often described as a ratio of rise to run or as an angle.

Softening point of bitumen is the temperature at which it becomes soft enough to flow, and it is determined using test methods like the ring-and-ball or Mettler cup-and-ball tests.

Solid content of an adhesive refers to the weight percentage of the nonvolatile matter in it.

Solubility is how well a substance can dissolve in a particular liquid under specific circumstances.

Solvent is a liquid that can dissolve other substances.

Spalling is when plate-like pieces break off from a concrete, rock, or masonry surface.

Specification is a detailed statement of requirements for a material, product, system, or service. It outlines what needs to be satisfied.\

Splice bonding is a method of joining overlapping materials.

Square is a unit of measurement for roof area that equals 100 square feet or the amount of material needed to cover a 100 square foot roof deck.

Squeegee is a tool with a leather or rubber blade on a handle used for spreading or wiping liquid material off a surface; it can also be used to smooth or treat a surface.

Staining is when foreign material causes discoloration on a roof membrane or coating.

Starter sheet is a narrow strip of material used to begin the shingling pattern at the edge of a roof. It is also used for perimeters in certain single-ply systems.

Styrene Butadiene Styrene Copolymer (SBS) is a high molecular weight copolymer that has both thermoset and thermoplastic properties. It is made by combining styrene and butadiene monomers through block copolymerization. SBS is commonly used as a modifying compound in asphalt roofing membranes to give them rubber-like qualities.

Substrate is the surface where a roofing or waterproofing membrane is installed, like the structural deck or insulation board in roofing.

Sump is a deliberate dip around a roof drain or scupper that helps with drainage.

Surfacing is the top layer of a roof that is meant to protect the underlying roofing from weather exposure.

T

Tapered insulation is a pre-cut or pre-molded insulation system that adds slope to the roof deck, allowing for easier installation of the roof membrane.

Taping is used to connect insulation boards or deck panels and to seam single-ply membranes.

Tear resistance is the amount of force needed to tear a material when stress is focused on a small area due to a flaw or notch.

Tensile strength is the ability of a material to withstand tension, not compression or shear.

Termination is the process of securing and sealing the edges of a membrane in a roof or waterproofing system.

Test Method A is a clear and specific procedure used to determine and assess the qualities, characteristics, or properties of a material, product, system, or service, resulting in a test result.

Thermal barrier pertains to torched membrane applications, a thermal barrier is added to the roof system before torching to enhance fire safety. Acceptable thermal barriers include perlite board insulation, fiberglass or mineral wool board insulation, or glass-faced gypsum board.

Thermal conductance is the rate at which heat flows through a material due to a temperature difference. It is measured in Btu/h•ft2•F and applies to a specific thickness of a specific material. It is incorrect to multiply or divide conductance values for different thicknesses of the same material, and it is also incorrect to add conductance values to determine overall thermal performance. To determine overall performance, convert conductance values to thermal resistance values and then add them together.

Thermal conductivity (k) is the measure of how well a material conducts heat. It is the amount of heat that passes through a 1-inch thickness of a 1-square-foot sample of material in one hour, with a temperature difference of 1 degree Fahrenheit between the two surfaces. It is expressed as Btu•inch/h•ft2•F. It is important to note that the thermal conductivity value only applies to a specific thickness of a material and cannot be directly used to determine the thermal performance of a different thickness of the same material. To determine the thermal performance of a specific thickness, the thermal conductivity value can be converted to a thermal resistance (R) value (R = 1/k) and then used in mathematical calculations.

Thermal cycling refers to the fluctuation of material or system stress caused by recurring temperature changes, resulting in displacements.

Thermal expansion is when a body increases in size or volume due to changes in temperature.

Thermal insulation is a material that helps to reduce heat flow.

Thermal movement refers to how materials change in size due to temperature changes.

Thermal resistance (R) is a measure of how well a material or construction can prevent heat flow. It is expressed in F•ft2•h/Btu and applies to a specific thickness. The thermal resistance (R) is the reciprocal of the thermal conductance (C) and can be mathematically manipulated.

Thermal transmittance (U-factor) is the measure of heat transmission through a material or construction, including the air films surrounding it. It is expressed in Btu/h•ft2•F and is the reciprocal of overall thermal resistance. It is used to assess the overall thermal performance of a system, such as a roof assembly. In some cases, it is referred to as the overall coefficient of heat transfer.

Thermoplastic is a material that becomes soft when heated and hardens when cooled, as long as it doesn’t reach the point of decomposition.

Thermoplastic Olefin Membrane (TPO membrane) is a blend of polypropylene and ethylene-propylene polymers with additives like colorant, flame retardants, and UV absorbers. It can be reinforced or not depending on the desired properties.

Thermoset polymers are a type of material that become solid and cannot be melted or dissolved when exposed to heat or chemicals.

Through-wall flashing is a waterproof barrier that goes through a wall, directing water outside through weep holes.

Tie-in is a seal used in roofing and waterproofing to connect different parts and ensure a watertight finish.

U

UL label is a seal affixed to roofing products to show they meet performance criteria, authorized by Underwriters Laboratories Inc.

Unforeseen conditions refer to unexpected situations or physical conditions that were not predicted in the contract documents and are different from what is typically encountered.

UV degradation refers to the harm caused by the sun’s ultraviolet rays.

V

Vapor pressure is the pressure exerted by a vapor in equilibrium with a liquid or solid.

Vapor retarder is a layer of material or laminate that helps to significantly reduce the amount of water vapor that enters a roof assembly.

Veneer is a type of masonry or plywood used for facing purposes, without structural connection. It can be made by gluing together thin layers of wood.

Viscosity is a material’s resistance to flow under stress, measured in centipoise (cP or cPs) at a specific temperature. As viscosity increases, flow rate decreases.

Void is an empty space or interruption in something.

W

Walkways are high-traffic areas on rooftops that are often near vents, hatches, and air-conditioning units. They can be made of materials like traffic mats or pavers to protect the roof from damage caused by people walking on it.

Water table is the level underground where the soil becomes saturated with water.

Water vapor pressure is the pressure of water vapor in the air, which adds to the overall atmospheric pressure.

Water vapor transmission is a measurement of how quickly water vapor can pass through a material in controlled lab conditions. It is typically measured in grains per hour per square foot.

Waterproofing treatment is applied to surfaces or structures to stop water from seeping through under pressure.

Waterproofing assembly consists of different components such as the deck, membrane, and protection/drainage/insulation course. These components work together to provide waterproofing for a structure.

Waterproofing membrane is the main component of a waterproofing system that keeps water out, without including extra accessories like drainage materials or protection boards.

Waterproofing system is made up of several components, including a membrane, protection, drainage, insulation, waterstops, joints, flashings, and overburden. It does not include the substrate.

Wet film gauge is a tool used to measure the thickness of wet coating on a flat smooth surface.

Wet film thickness refers to the thickness of a coating or mastic when it is applied but not yet cured. It is measured in mils.

Wind lift pertains to when wind is deflected at roof edges, peaks, or obstructions, it creates a drop in air pressure above the roof surface, known as wind uplift.

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