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Last Updated: 09/22/2026

Commercial and Industrial Roof Coatings Certificate Program

AirSprayTech Academy Certificate Program

Commercial and Industrial Roof-Coating Glossary

Commercial and Industrial Roof Coatings for Professional Roof Coaters
Article 25 of 25

Roof-coating specifications, technical data sheets, approval reports, warranties, and inspection documents use specialized terminology. Understanding exactly what those terms mean helps contractors select, estimate, install, inspect, and document modern fluid-applied roof systems.

Why Terminology Matters

Similar-sounding roofing terms are not always interchangeable. A coating is not automatically a membrane. Elastomeric is not one specific coating chemistry. Coverage rate is not the same as finished dry-film thickness. A product warranty is not necessarily a roof-system warranty.

Misunderstanding one technical word can result in incorrect material selection, inaccurate estimating, insufficient thickness, rejected work, or lost warranty coverage.

Contractor principle: When a term affects system selection, preparation, thickness, testing, acceptance, or warranty, confirm its meaning in the project specification and the manufacturer’s current written documents.

Quick Alphabetical Navigation

A B C D E F G H I L M N O P R S T U V W

A

Abrasion resistance: The ability of a cured coating to resist surface wear caused by foot traffic, maintenance activity, windblown particles, equipment, or repeated physical contact. Abrasion resistance does not establish puncture resistance or resistance to every form of mechanical damage.
Absorption: The process by which a liquid enters or is taken into a material. Porous concrete, masonry, insulation, and some roofing materials can absorb water or liquid coating.
Adhesion: The strength of the bond between two different materials, such as a primer and substrate or a coating and existing membrane. Adhesion should be distinguished from cohesive strength within a material.
Adhesive failure: Separation at the interface between two different materials. Examples include coating separating from a metal panel or a finish coat separating from a base coat.
Acrylic roof coating: A usually water-based coating using acrylic-polymer chemistry. Acrylic roof coatings are commonly selected for ultraviolet resistance, reflectivity, color retention, and application over approved roof substrates. Cure depends on water evaporation and suitable weather conditions.
Aggregate: Granular material incorporated into or broadcast onto a coating. Aggregate may be used to improve slip resistance, surface durability, texture, or ultraviolet protection. Its use must be approved for the roof system.
Airless spray: A spray method that atomizes coating by forcing it through a small spray-tip orifice at high fluid pressure without using compressed air at the spray tip.
Aliphatic polyurethane: A polyurethane formulated with aliphatic chemistry, generally selected where ultraviolet stability and color retention are important. It should not be confused with aromatic polyurethane.
Ambient temperature: The temperature of the air surrounding the work area. Ambient temperature is different from roof-surface temperature and material temperature.
Application rate: The quantity of material applied over a stated area, commonly expressed as gallons per 100 square feet. Application rate must be considered with solids content, substrate texture, waste, and required finished thickness.
Approved equal: A proposed product or system that has been formally evaluated and accepted as satisfying the project requirements. Similar chemistry or published properties alone do not make a product an approved equal.
Aromatic polyurethane: A polyurethane based on aromatic isocyanate chemistry. Aromatic polyurethanes may provide strong physical properties but can change color or chalk under ultraviolet exposure unless protected by an approved ultraviolet-resistant topcoat.

B

Base coat: A coating layer installed before the finish coat. Depending on the system, it may provide reinforcement embedment, film build, adhesion, waterproofing, or part of the specified membrane thickness.
Bleed-through: Migration of asphalt, oils, dyes, plasticizers, or other substances from the substrate into or through a newly applied coating. A compatible blocking primer may be required.
Blister: A raised area caused by loss of adhesion or expansion beneath a coating or membrane. Possible causes include trapped moisture, vapor pressure, outgassing, contamination, solvent entrapment, or application over an unsuitable substrate.
Broadcast: The placement of granules, sand, aggregate, or another solid material into a wet coating. Broadcast materials should be compatible with and approved for the roof system.
Building envelope: The collection of roof, wall, window, door, foundation, air-control, water-control, vapor-control, and thermal-control assemblies that separate the building interior from exterior conditions.

C

Catalyst: A substance that initiates, accelerates, or modifies a chemical reaction. Catalyst quantities must not be changed unless specifically permitted by the manufacturer.
Chalking: Formation of a loose, powdery material at the surface of a coating, usually caused by weathering and degradation of the binder. Chalking can interfere with adhesion of a new coating.
Coating: A liquid-applied material that forms a continuous film after curing. Depending on its formulation and installed thickness, a coating may provide protection, reflectivity, weathering resistance, or part of a fluid-applied roof membrane.
Cohesion: The internal strength holding a material together. Cohesive failure occurs within one material rather than at the interface between two different materials.
Compatibility: The ability of two materials to remain in contact without harmful chemical or physical interaction. Compatibility does not necessarily prove adequate adhesion or long-term system performance.
Condensation: Water formed when moisture in the air contacts a surface at or below the air’s dew-point temperature. Condensation can interfere with coating adhesion, cure, and appearance.
Coverage rate: The area a stated volume of material is expected to cover, often expressed as square feet per gallon or gallons per 100 square feet. Published coverage may be theoretical and may not include waste, surface texture, overspray, corrugation, or reinforcement saturation.
CRRC: Cool Roof Rating Council. The CRRC operates a product-rating program that reports solar reflectance and thermal emittance values for roofing products. A CRRC rating is not, by itself, a complete building-code or roof-system approval.
Cure: The chemical or physical process through which an applied coating develops its intended properties. Cure is not always the same as surface drying.
Cure time: The time required for a coating to reach a specified stage of cure. Cure time can be affected by temperature, humidity, film thickness, ventilation, moisture, and coating chemistry.

D

Deck: The structural roof surface that supports insulation and the roofing system. Common decks include steel, concrete, wood, gypsum, and cementitious wood-fiber products.
Delamination: Separation between layers within a roof, coating, or membrane system. Delamination can occur at the substrate, primer, intercoat, adhesive, reinforcement, insulation, or existing-roof interface.
Dew point: The temperature at which air becomes saturated and condensation can begin forming. Roof-surface temperature should remain above the manufacturer- or specification-required margin over the dew point.
DFT: Dry-film thickness. The thickness of a coating after it has cured and volatile components have left the film. DFT is commonly reported in mils or micrometers.
Drainage: The roof’s ability to direct water toward drains, scuppers, gutters, or other discharge points. A coating should not be represented as a correction for structural slope or defective drainage unless the approved scope specifically provides that correction.
Drying time: Time required for a coating to lose water or solvent and reach a stated surface condition. A coating may appear dry before it has developed full cure or physical properties.

E

Elastomeric: Describes a material capable of stretching and recovering to a useful degree. Elastomeric is a performance description—not one particular coating chemistry. Acrylic, silicone, polyurethane, polyurea, and other chemistries may be formulated with elastomeric properties.
Elongation: The increase in length a material can sustain before breaking, commonly expressed as a percentage. High elongation alone does not establish durability, tensile strength, crack-bridging ability, or suitability for a particular roof.
Efflorescence: A crystalline deposit of soluble salts carried to the surface by moisture moving through concrete, masonry, or another cementitious material. Efflorescence can indicate moisture movement and interfere with coating adhesion.
Emulsion: A mixture in which one liquid is dispersed within another liquid. Many water-based acrylic coatings are polymer emulsions.
Expansion joint: A designed building or roof joint that accommodates movement between structural sections. It generally requires a purpose-designed joint assembly and should not simply be filled or bridged with ordinary roof coating.

F

Feather edge: A tapered transition from a repair or coating layer to the adjacent surface. Feathering can reduce abrupt edges but must not create a film thinner than the system’s minimum requirement.
Finish coat: The final exposed coating layer. It may provide color, reflectivity, ultraviolet resistance, weathering protection, chemical resistance, and part of the required system thickness.
Flashing: Materials and configurations used to weatherproof roof transitions, edges, walls, penetrations, curbs, drains, and changes in plane. Flashing must accommodate anticipated movement and direct water onto the roof surface.
Fluid-applied membrane: A liquid-applied material or combination of materials installed to form a continuous, fully adhered membrane. A fluid-applied membrane normally has defined requirements for substrate preparation, primer, reinforcement, thickness, details, cure, and quality control.
FM Approved: A designation indicating that a product or assembly has satisfied applicable FM Approvals testing and listing requirements. The exact approved assembly and its limitations must be verified in the current FM Approval Guide.

G

Galvanic corrosion: Corrosion resulting from electrical interaction between dissimilar metals in the presence of an electrolyte such as water. Proper metal selection, separation, drainage, and protective coatings may be required.
Granulated cap sheet: A bituminous roofing sheet with mineral granules embedded in its exposed surface. Loose granules, asphalt bleed, surface texture, and retained moisture must be considered before coating.
Green roof: A roof assembly incorporating vegetation and growing media. This is different from a roof described as environmentally preferable, reflective, or energy efficient.

H

Hardness: A material’s resistance to indentation, penetration, or scratching. Greater hardness does not automatically mean greater flexibility, impact resistance, or durability.
Holiday: A discontinuity such as a pinhole, void, thin area, gap, or break that interrupts the protective coating or membrane.
Holiday detection: Testing intended to locate discontinuities in a cured coating or membrane. The proper equipment and voltage depend on coating thickness, conductivity, substrate, and manufacturer approval.
Humidity: The amount of moisture present in the air. Relative humidity affects evaporation, condensation risk, cure, and application windows.
Hydrostatic pressure: Pressure exerted by a standing column of liquid. It is different from moisture-vapor transmission, although both can contribute to coating or membrane failure.

I

Infrared roof survey: A nondestructive survey method that identifies thermal patterns that may indicate moisture differences within a roof assembly. Suspected areas normally require correlation and confirmation.
Intercoat adhesion: Adhesion between separate coating layers. Intercoat adhesion can be affected by contamination, weathering, surface texture, cure, and exceeded recoat windows.
Isocyanate: A reactive chemical group used in many polyurethane and polyurea materials. Isocyanate-containing products require strict exposure control, PPE, respiratory protection, handling, and safety procedures.

L

Lap: The overlap between adjacent sheets, panels, reinforcement pieces, or membrane sections. Laps must be prepared and detailed according to the approved roof system.
Latent moisture: Moisture concealed within insulation, roofing, concrete, deck components, or other parts of the assembly that is not visible during an ordinary surface inspection.
Low-slope roof: A roof with a relatively small slope that uses roof coverings designed for hydrostatic or near-hydrostatic water exposure. Applicable code definitions and system limitations should be verified.

M

Manufacturer-authorized contractor: A contractor recognized by a manufacturer for specified products or systems. Authorization requirements and status vary and should be confirmed directly with the manufacturer for the project.
Material safety data sheet: An older term commonly replaced by Safety Data Sheet under the standardized hazard-communication format.
Membrane: A continuous layer designed to control water entry. A membrane may be sheet-applied or fluid-applied and may incorporate primer, reinforcement, base coat, and finish coat.
Mil: One-thousandth of an inch: 0.001 inch. One mil is approximately 25.4 micrometers. A 20-mil film is 0.020 inch thick.
Mil gauge: A tool used to measure coating thickness. Wet-film gauges, magnetic dry-film gauges, eddy-current gauges, and destructive thickness tools operate differently and are not interchangeable.
Mockup: A representative installation used to demonstrate preparation, appearance, details, workmanship, adhesion, application procedures, or acceptance criteria before full production.
Moisture-vapor transmission: Movement of water vapor through a material or assembly due to vapor pressure differences. It is not the same as liquid leakage or hydrostatic pressure.

N

NDL warranty: No-dollar-limit warranty. This generally means the warranty does not state a fixed maximum dollar amount for covered repairs. It does not eliminate exclusions, owner obligations, reporting requirements, or other warranty limitations.
Nominal thickness: A stated or target thickness that may permit defined variation. It should not automatically be interpreted as a minimum thickness.
NRCA: National Roofing Contractors Association. NRCA publishes roofing manuals, guidelines, technical information, safety resources, and contractor education.

O

Osmotic blistering: Blistering associated with water movement through a coating toward soluble material or contamination beneath it. Osmotic pressure can cause separation even when no obvious roof leak is present.
Outgassing: Release of air, moisture vapor, solvent, or other gas from a porous or heated substrate into a wet coating. Outgassing can create bubbles, pinholes, craters, or blisters.
Overcoat: Application of a new coating layer over an existing coating or roof surface. The existing system must be evaluated for condition, compatibility, adhesion, moisture, and preparation.
Overspray: Atomized coating that travels beyond the intended application area. Overspray can damage vehicles, equipment, windows, air intakes, adjacent property, and finished building surfaces.

P

Permeability: A material property describing the rate of water-vapor transmission through a unit thickness under stated conditions.
Permeance: The rate of water-vapor transmission through a specific material thickness or assembly under stated conditions, commonly reported in perms.
Pinholing: Formation of small holes through or into a coating film. Possible causes include substrate porosity, outgassing, inadequate thickness, air entrapment, poor application, or unsuitable viscosity.
Ponding water: Water that remains on a roof beyond the drainage period defined by the project, manufacturer, code, or applicable standard. Definitions and warranty treatment vary; the controlling documents must be checked.
Polyurea: A rapid-reacting coating or membrane chemistry formed through the reaction of an isocyanate component with an amine-resin component. Polyurea systems commonly require specialized proportioning and spray equipment.
Polyurethane: A coating or membrane chemistry formed through a reaction involving an isocyanate component. One-component moisture-cured and multi-component polyurethane products have different application, cure, and equipment requirements.
Pot life: The usable time available after reactive components are mixed. Material can become unsuitable before it becomes visibly solid or unworkable.
Primer: A material applied before subsequent layers to improve adhesion, seal porosity, inhibit corrosion, block staining, or condition the substrate. Primer selection is substrate- and system-specific.
Profile: The surface texture or roughness produced by preparation. Excessive or insufficient profile can affect coating coverage, adhesion, and finished thickness.
Puncture resistance: The ability of a material or assembly to resist penetration by a concentrated load or sharp object. It is different from tensile strength, hardness, and abrasion resistance.

R

Recoat window: The time period during which another coating layer may be applied without additional preparation. Applying too early or after the window has expired can affect cure and intercoat adhesion.
Reflectance: The fraction of incoming solar energy reflected by a surface. Solar reflectance is commonly expressed as a decimal or percentage.
Reinforcement: Fabric, mesh, scrim, mat, or fibers incorporated into a fluid-applied system to improve strength, crack bridging, dimensional stability, or detail performance.
Relative humidity: The amount of water vapor in the air compared with the maximum amount the air could hold at the same temperature, expressed as a percentage.
Repair: Localized corrective work intended to restore a damaged or deficient component. A repair should address the cause, extend to sound material, and remain compatible with the surrounding roof system.
Roof coating: A liquid-applied material intended to protect, renew, weatherproof, or modify the surface properties of an approved roof substrate. Whether it functions as a complete roof membrane depends on the system design, installed thickness, reinforcement, approvals, and manufacturer requirements.
Roof restoration: Work performed to return an existing, serviceable roof assembly to an acceptable condition and extend its useful service life. Restoration may include repairs, reinforcement, primer, and coating, but it does not make a failed or saturated roof suitable without correction.

S

Sag: Downward movement of wet coating that produces an uneven, thickened film. Sags can result from excessive film build, low viscosity, unsuitable spray technique, or application on vertical surfaces.
Safety Data Sheet: The standardized document describing product hazards, exposure controls, PPE, storage, first aid, firefighting, spill response, and other safety information. Common abbreviation: SDS.
Sealant: A material used to seal joints, gaps, penetrations, or transitions. Sealant must be selected for movement, substrate compatibility, exposure, joint configuration, and compatibility with adjacent coatings.
Seam: The joint between adjacent sheets, panels, membrane sections, or components. Seam preparation and reinforcement are critical parts of many restoration systems.
Silicone roof coating: A moisture-curing or otherwise reactive coating using silicone chemistry. Silicone roof coatings are commonly selected for ultraviolet and weather resistance and may be approved for exposure to ponding water under specific manufacturer requirements.
Solar reflectance: The fraction of solar energy reflected by a roof surface. It does not describe thermal emittance, insulation value, waterproofing, or the complete energy performance of the building.
Solids by volume: The percentage of a liquid coating’s volume theoretically remaining as cured film after volatile components leave. It is used to estimate the relationship between wet-film and dry-film thickness.
Solids by weight: The percentage of coating weight remaining after volatile components are removed. It should not be substituted for solids by volume when calculating film thickness.
SPF: Spray polyurethane foam. In roofing, SPF is spray-applied to form insulation and a roofing substrate that must be protected by an approved coating system.
Substrate: The surface onto which a coating, primer, sealant, adhesive, reinforcement, or membrane is applied.
Surface preparation: Cleaning, drying, repairing, abrading, profiling, treating, or priming a surface so it is suitable to receive the specified material.
Surface temperature: The actual temperature of the roof surface being coated. It may be considerably higher or lower than the surrounding air temperature.

T

Tack-free time: The time required for a coating surface to reach a condition in which it no longer feels tacky under the specified test or manufacturer criteria. Tack-free does not necessarily mean fully cured.
Tear strength: A material’s resistance to the growth of a cut or tear. Tear strength is distinct from tensile strength and elongation.
Technical Data Sheet: The manufacturer’s published document describing product uses, properties, coverage, application, limitations, packaging, storage, and cure. Common abbreviations include TDS and PDS.
Tensile strength: The maximum tensile stress a material can withstand under the stated test conditions. It should be evaluated with elongation, tear resistance, thickness, weathering, and system design.
Termination: The location and method by which a roof membrane or coating system ends and is secured, sealed, or integrated with another component.
Thermal cycling: Repeated expansion and contraction caused by temperature changes. Roof materials may move at different rates, placing stress on seams, coatings, flashings, and penetrations.
Thermal emittance: A surface’s ability to release absorbed heat as infrared radiation. It is a separate property from solar reflectance.
Thermal shock: Rapid temperature change that produces stress in a material or assembly, such as cold rain striking a hot roof.
Two-component coating: A reactive material supplied in separate components that must be proportioned and mixed or plural-component sprayed in the specified ratio.

U

UL classification: A classification based on evaluation by UL for stated requirements. The contractor must verify the exact product or roof assembly, classification, construction details, and limitations.
Ultraviolet degradation: Deterioration caused by exposure to ultraviolet radiation. Effects can include chalking, fading, cracking, embrittlement, erosion, and loss of physical properties.
Urethane: A commonly used shortened term for polyurethane. The exact chemistry, component structure, cure mechanism, and ultraviolet resistance should be confirmed.

V

Vapor drive: The force produced by differences in vapor pressure that causes water vapor to move through materials or assemblies.
Vapor retarder: A material or assembly that limits water-vapor diffusion. Vapor retarders are classified by permeance and must be located and integrated appropriately for the building and climate.
Viscosity: A measure of a liquid’s resistance to flow. Coating viscosity affects pumping, atomization, leveling, sagging, mixing, and application rate.
VOC: Volatile organic compound. VOC content and emissions may be regulated and are reported according to defined test methods and regulatory requirements.
Volume solids: See Solids by volume. This value is used when estimating theoretical dry-film thickness from wet-film thickness.

W

Warranty: A written statement defining specified obligations, coverage, exclusions, remedies, duration, and conditions. Product, workmanship, material-only, labor-and-material, system, and NDL warranties provide different coverage.
Weathering: Changes in a material resulting from outdoor exposure, including ultraviolet radiation, heat, water, freeze-thaw cycling, pollutants, wind, and biological growth.
Wet-film thickness: The thickness of a coating immediately after application and before drying or curing. Common abbreviation: WFT.
Wind uplift: Pressure acting to lift the roof assembly from the building. Required resistance depends on building location, height, geometry, roof zones, deck, attachment, and applicable code requirements.
Witness plate: A removable or retained test surface placed in the application area to provide a representative coating sample for thickness, cure, or other evaluation. Its use and interpretation should be established by the project procedure.

Words That Change the Requirement

Specifications use certain words deliberately. Contractors should not treat them as interchangeable.

Term	Practical Meaning
Shall or must	Establishes a mandatory requirement unless the contract defines the term differently.
Should	Generally identifies a recommendation rather than an absolute requirement, although context must be checked.
May	Generally indicates permission or an available option, not a mandatory action.
Minimum	Establishes the lowest acceptable value. An average value does not correct individual readings below a stated minimum unless the acceptance procedure permits it.
Maximum	Establishes a value that must not be exceeded.
Nominal	Describes a named or target value that may include an established tolerance.
Typical	Describes a representative value or condition and should not automatically be interpreted as a guaranteed result.
Approximately	Indicates an estimate. It should not replace a stated minimum, maximum, or required field measurement.
As required	Means the quantity or action is determined by actual conditions or another controlling requirement. It does not mean the item is optional.
Approved	Accepted by the person or organization identified in the contract. Contractor preference alone is not approval.
Verify	Confirm the condition, measurement, dimension, product, or requirement rather than assuming it is correct.
Provide	Commonly means furnish and install complete, unless the project definitions state otherwise.

Frequently Confused Terms

Terms	Important Difference
Elastomeric and acrylic	Elastomeric describes a material property. Acrylic identifies a chemical family. An acrylic coating can be elastomeric.
Coating and membrane	A coating forms a film. A membrane is designed as a continuous water-control layer. Whether a coating becomes part of a membrane depends on the complete system.
Dry and cured	A surface can feel dry before the material has developed full cure and physical properties.
Coverage and thickness	Coverage describes material quantity over area. Thickness describes the resulting film. Texture, waste, solids, and application conditions affect the relationship.
Adhesion and compatibility	Compatible materials may not damage each other, but they may still have inadequate adhesion.
Solar reflectance and thermal emittance	Reflectance describes reflected solar energy. Emittance describes the release of absorbed heat.
Product warranty and system warranty	A product warranty addresses the manufactured material. A system warranty may address defined performance of an approved installed assembly.
Material delivered and material installed	Purchase or delivery records do not prove how much material was applied to the roof.
Moisture vapor and hydrostatic pressure	Vapor is moisture in gaseous form moving because of vapor pressure. Hydrostatic pressure is created by liquid water.
Ponding-water resistance and drainage correction	Resistance to ponding water does not mean that coating corrects inadequate slope or defective drainage.

Common Abbreviations

ASTM: ASTM International

CRRC: Cool Roof Rating Council

DFT: Dry-Film Thickness

FM: FM Approvals

HVAC: Heating, Ventilation, and Air Conditioning

ICC-ES: ICC Evaluation Service

NDL: No Dollar Limit

NRCA: National Roofing Contractors Association

PDS: Product Data Sheet

PPE: Personal Protective Equipment

RFI: Request for Information

RH: Relative Humidity

SDS: Safety Data Sheet

SPF: Spray Polyurethane Foam

TDS: Technical Data Sheet

UL: UL Solutions

UV: Ultraviolet

VOC: Volatile Organic Compound

WFT: Wet-Film Thickness

Technical References and Industry Resources

Definitions can vary among standards, codes, specifications, manufacturers, warranty documents, and regulatory agencies. When a project document provides a specific definition, that definition should be used for that project.

Article 25 Takeaway

Professional roof coating requires a shared technical language. Contractors who understand the difference between chemistry, performance, thickness, coverage, adhesion, cure, approvals, and warranties are better prepared to recognize risk and deliver a defensible roof system.

This glossary completes the 25-article course. Keep it available as a field reference when reviewing specifications, technical data sheets, inspection reports, proposals, and warranty requirements.

Course Articles Complete

You have reached Article 25 of 25 in the Commercial and Industrial Roof Coatings for Professional Roof Coaters series.

You may review any course article or proceed directly to the course assessment. A score of 80% or higher is required to pass.

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No part of this article may be reproduced, distributed, transmitted, stored, republished, or used in any form or by any means without the prior written permission of Azimuth Spray Systems, LLC, except for brief quotations used for review, education, or reference with proper attribution.

This educational material does not replace project specifications, engineering, manufacturer instructions, technical data sheets, safety data sheets, building codes, regulations, testing requirements, contract documents, warranty documents, or professional judgment. Product and manufacturer references are provided for education and do not constitute endorsement.

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Tags: roof coating glossary, roofing terminology, elastomeric coating, acrylic roof coating, silicone roofing, polyurethane roof coating, fluid-applied roofing

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