When Does a Roof Coating Make More Sense than a Roof Replacement?

Liquid-applied roof membranes (LAM) and roof coatings (aka, maintenance coatings) are not only here to stay, their use is on the rise. This blog takes a look at how the building code and the roofing industry generally differentiate between liquid-applied roof membranes and roof coatings. There is confusion because the intended use of each is different, yet many of the materials are the same for both applications. Here's what you need to know to help understand and differentiate between the two.IntroductionCoatings have been used in the construction and roofing industries for a very long time! They have been made from many different materials--from beeswax and pitch some 5000 years ago, to lacquers and varnishes just a couple thousand years ago, to our current polymer-based materials. According to the Roof Coating Manufacturers Association, "the most dramatic advance in coating properties has come in the past 40 years, with the development of polymers1." Polymer-based coatings are used on plaza decks, parking garages, balconies, playgrounds, and roofs, for example, to provide a level of water-resistance and an aesthetically pleasing surface. Polymer-based liquid-applied membranes are used as the water-proofing layer for new roofs, replacement roofs, and roof re-cover systems. The common polymer-based materials include acrylics, silicones, and urethanes. More information about these materials can be found here.The spotlight is on these types of polymers because the materials we use for coatings are quite often also being used as liquid-applied membranes. How do we categorize and define these different installations that have different intended uses when both applications use essentially the same set of materials? This blog takes a close look at each of these product categories—coatings and liquid-applied membranes—to find their similarities and differences. And hopefully to provide clarity around the use of terms and definitions of use.Market ShareIn 2017, The Freedonia Group published a research study titled, "Liquid-Applied Roof Coatings in the US by Product and Subregion." According to that report, 11.85 million squares (1.185 billion square feet) of liquid-applied roof coating were installed in 2016. Approximately 40% was installed in the South, with the remainder essentially evenly split between the Northeast, Midwest, and West regions.The Freedonia Group reported a number of key findings that help explain the increased use of coatings."The South will be the leading US regional market for roof coatings in 2021, boosted by a high level of interest in cool roofing products and in protecting roofs against storm damage.The West will see solid growth as communities amend building codes to mandate the use of cool roofing.Liquid-applied roof coating demand in the Midwest and Northeast will be supported by rising use of roof coatings to rejuvenate older roofs instead of engaging in more costly reroofing projects."Note: The Freedonia Group's report does not separate market share based on liquid-applied materials used as roof coatings versus liquid-applied materials used as roof membranes.The use of coatings and liquid-applied membranes is increasing for a number of additional reasons as well.The use of materials that can be applied at ambient temperature is welcomed by an installer. There are no super-heated materials or open flames therefore reducing specific safety concerns.Materials are typically provided in containers sized for easy transport to and from rooftops.Common low-cost installation tools are used—brooms, brushes, squeegees; and simple, low-cost spray equipment.Using liquid-applied membranes can reduce waste created by a tear off.These materials are commonly light colored so they are reflective to help improve energy efficiency.Depending on the design (intent) and application of polymer-based materials, they can be used to extend the life of an existing roof when used as a coating, or to provide a warranted or guaranteed, waterproofing roof covering when used as a liquid-applied membrane.Defining the TermsOne way to help sort out the difference between coatings and liquid-applied membranes is to understand current definitions used in the industry. The International Building Code (IBC) is a good place to start since it is considered to be consensus-based.International Building CodeThe International Building Code does include a definition for coating, but does not include a definition for liquid-applied membrane."ROOF COATING. A fluid-applied, adhered coating used for roof maintenance or roof repair, or as a component of a roof covering system or roof assembly."IBC's definition of Roof Coating tells us three things.Coatings are fluid-applied and adhered (to a substrate)Coatings are used for maintenance or repair "Roof Repair" is defined as "Reconstruction or renewal of any part of an existing roof for the purposes of correcting damage or restoring pre-damage condition." Coatings can be a component of a roof system or roof assembly (which are the same according to ICC's definitions) "Roof Assembly" is defined as "A system designed to provide weather protection and resistance to design loads. The system consists of a roof covering and roof deck or a single component serving as both the roof covering and the roof deck. A roof assembly can include an underlayment, a thermal barrier, insulation or a vapor retarder." "Roof Covering" is defined as "The covering applied to the roof deck for weather resistance, fire classification or appearance." "Roof Covering System" is a "Roof Assembly" per IBC. Realistically, IBC's definition of Roof Coating doesn't get us that much closer to differentiating coatings and liquid-applied membranes, except that coatings are intended for maintenance and repair. And per IBC's definition, coatings can be used for Roof Repairs to "correct damage or restore pre-damage condition," but that is not how coatings are generally intended to be used.Taking a look at how Chapter 15 of IBC is arranged gives a bit of insight into IBC's perspective on coatings and liquid-applied membranes. Section 1507, Requirements for Roof Coverings, has and continues to include all low-slope and steep-slope materials used as roof coverings that are recognized by the code. This includes materials such as asphalt, wood, and slate shingles, as well as modified bitumen and single-ply roofing (and myriad others). The ICC has always included a section specifically for Liquid-applied Roofing within Section 1507, but there has never been a section for Coatings (until this year—more on that in a bit). To that end, the IBC is essentially saying Liquid-applied Membranes are categorized similarly to all other membranes that are used as roof coverings and their intended use is for "weather resistance, fire classification or appearance" (from IBC's definition as shown above). Because liquid-applied membranes are considered to be roof coverings, roof systems that use a liquid-applied membrane need to be tested for fire, wind, and impact… like any traditional membrane roof system.The liquid-applied membrane subsection within Section 1507 includes ASTM standards for materials not only used as liquid-applied membranes, but it includes the polymer-based materials (e.g., acrylics, polyurethanes, silicones) that are also intended to be used as coatings. This led to confusion within the code requirements, specifically how code officials would enforce the application of a coating product on an existing roof--as a new roof or as a maintenance item.To help with clarification and code enforcement, new language was added to the 2018 IBC in the Reroofing Section that stated a roof coating can be applied to (essentially) any existing roof without triggering reroofing requirements. The 2015 IBC and earlier versions only stated that coatings could be applied over an existing Spray Polyurethane Foam without removing any existing roofs. The IBC 2018 code language is as follows:"Section 1511.3, Roof Replacement. Exception 4: The application of a new protective roof coating over an existing protective roof coating, metal roof panel, built-up roof, spray polyurethane foam roofing system, metal roof shingles, mineral-surfaced roll roofing, modified bitumen roofing or thermoset and thermoplastic single-ply roofing shall be permitted without tear off of existing roof coverings."The additional language in the 2018 IBC was a very important step in distinguishing between coatings and liquid-applied membranes.The I-Codes were further revised regarding coatings and liquid-applied membranes in the 2021 IBC; a new section was added--Section 1509, Roof Coatings. This was an entirely new section, and importantly, Roof Coatings are not a subsection within Section 1507, Roof Coverings. This strengthens the differentiation from a code perspective that coatings are not considered to be a new roof covering. However, the IBC 2021 remains without a definition for liquid-applied roofing or liquid-applied membrane. The code ultimately relies on manufacturers' intentions for their products as the differentiating factor between coatings and liquid-applied membranes.ASTMUnfortunately, ASTM D1079, "Standard Terminology Relating to Roofing and Waterproofing" does not define either term.Industry PerspectiveWhat does GAF, a leading supplier of both systems, say about each? From GAF's page, Liquid-Applied Coating Solutions, the following descriptions are provided."What is a Liquid Membrane Roofing System?A liquid-applied roofing system consists of multiple components that come together to form a fully adhered, seamless, and self-flashing membrane. Components include liquid applied coatings and mesh membranes to create a true liquid membrane system that preserves and protects the integrity of the building." Examples of some of the leading products can be found here."What is a Roof Coating System?Roof Coatings are designed for extending the life of existing structurally sound roofs. GAF Roof Coatings are specially formulated to extend the life of roofs while protecting them from damaging effects of weather and the environment such as UV light, water and wind. GAF offers roof coatings in a variety of different technologies such as acrylic, silicone and polyurethanes to meet many different building needs and budgets."According to GAF, a liquid-applied roofing membrane protects the integrity of the building (like any traditional membrane-type roof system) and coatings are designed for extending the life of structurally sound roofs.The Roof Coating Manufacturers Association (RCMA) has a thorough description of a roof coating. RCMA is appropriately focused on the makeup of a coating (i.e., higher solids content, high quality resins) to differentiate roof coatings from what is commonly called "paint." One concept from RCMA in particular stands out—because roof coatings are "elastomeric and durable films," they provide "an additional measure of waterproofing" and can "bridge small cracks and membrane seams." The roofing industry recognizes a coating's ability to provide an amount of weather resistance / restorative properties, but this characteristic (i.e., crack bridging) is difficult to test for and quantify. And it is worth repeating, a roof coating is primarily intended to extend the service life of structurally sound roofs, not necessarily be the waterproofing layer. That is the intent of a liquid-applied membrane.FM ApprovalsLiquid-applied membranes are considered to be roof coverings by the IBC, and therefore they must be tested and have approval listings. Approval listings are used to show that systems have been tested and comply with the code requirements for roof system properties like fire-, wind-, and impact-resistance.RoofNav—New ConstructionTo that end, performing a search using the Assembly Search function within FM's RoofNav software results in a number of Approval Listings for "Liquid Applied Systems" used for New Roofs. With no manufacturer selected, the RoofNav search resulted in more than 10,000 Approval Listings for liquid-applied roofs used for new construction!Performing a second search using GAF as the manufacturer results in nearly 250 Approval Listings for "Liquid Applied Systems" used as new roofs. The nearly 250 Approval Listings include applications primarily over DensDeck™ and spray foam. When a liquid-applied membrane is used over a substrate board, such as a DensDeck™ board, a reinforcing fabric embedded between two foundation coats is used. The use of the substrate board is more common for new construction or roof replacement projects and is not common when re-covering an existing roof.An example RoofNav listing is shown here. It includes a finish coat and foundation coat with fabric over DensDeck that is adhered to polyiso, and the polyiso is adhered to a concrete deck.Wind-uplift capacity of liquid-applied membrane roof systems can be quite high. The example above has a wind uplift rating of 270 psf! Where would such a high-capacity roof system even be needed? Here's a blog that discusses design wind pressures.RoofNav—Re-coverIn addition to their use as new roofing, one of the primary attributes of liquid-applied membranes is their use over an existing roof. Searching RoofNav using GAF and "Re-Cover" as the Application results in nearly 200 Approval Listings.If a liquid-applied roof system is used in a re-cover application, the use of the reinforcing fabric seems to be tied to the specific substrate. Looking through GAF's RoofNav Approval Listings for Re-cover Liquid-Applied Systems, reinforcing fabric is used when re-covering traditional multi-ply asphaltic membrane roof systems, or TPO and PVC membranes. However, when the substrate is a standing-seam type metal roof panel, a metal-faced composite panel, or spray foam, the fabric is not listed as a necessary component of an Approval Listing.It's important to recognize that an FM Approval Listing also provides information about the internal fire rating, exterior fire rating, and hail ratings. Many liquid-applied roof systems achieve Class A Exterior Fire ratings as well as Moderate or Severe Hail ratings. For a short tutorial on using RoofNav's Assembly Search feature, watch this video.In SummaryThe following chart is intended to provide examples of similarities and differences between coatings and liquid-applied membranes.ConclusionSimply put, coatings are used to provide protection from the elements and help extend service life. Coatings are not installed as 'membranes' so they are not intended to seal leaks or be considered "waterproof". Liquid-applied membranes are considered to be just that—membranes—and are used as the covering in new and re-cover roof systems. Liquid-applied membranes are tested as systems and have approval listings just like traditional asphaltic, modified bitumen, and single-ply roof systems.References:1RCMA.org/history-of-roof-coatings

Building owners have a lot to think about when selecting a roof for their commercial property. When it comes to commercial roofs, we have some information to help you understand what factors play a role in the roofing system's success, and its ability to protect the building, people and contents within it.1. ProductsThere are several different types of commercial roofing systems, and each has different benefits. A roofing professional can help building owners decide between the following roofing system types depending on the unique needs of the building:Single-ply: Single-ply membrane systems are the most popular commercial roofing material because single-ply is strong, durable, and provides robust protection against UV damage.Liquid-applied: Liquid-applied roofing systems are also strong and durable, and they're ideal for challenging roofs with a lot of equipment and penetrations. Ensuring flashing integrity and regular membrane cleaning can help extend the life of a liquid-applied roofing system.Modified-bitumen: A typical modified bitumen roofing system consists of two plies of roofing membrane. The membranes contain synthetic rubber which provides greater elongation than some other asphaltic systems. Modified-bitumen systems have a wide range of application methods, and can be hot-mopped, cold-applied, heat-welded or self-adhered.Built-up roofing: Built-up roofs are the oldest of the current roofing technology, and consist of melting bricks of hot asphalt in a large metal kettle and using mops to apply that asphalt in-between a multi-ply BUR system.It is recommended that all components of a roofing system are purchased from the same manufacturer. This helps ensure that the components are designed to work together. It also may make the system eligible for enhanced warranty or guarantee coverage from the manufacturer.2. EnergyThe rise of more stringent energy codes has increased the need for additional roof insulation and increased roof surface reflectivity. Increasing the amount of insulation in the roof and installing highly reflective roofing materials can help improve the energy efficiency of buildings.3. MaintenanceRegular roof maintenance may be required in order to keep your manufacturer's guarantee or warranty in effect.Maintenance programs can also help commercial building owners manage risk. Regular maintenance can help you address minor problems before they become expensive issues, which may ultimately help owners save money long-term.Maintenance staff should perform regularly scheduled roof inspections at all locations to ensure that the roof is still in good shape. Look for dents, tears, ponding water, or other signs of damage. Roof drains should be cleared regularly to ensure that water is allowed to drain unimpeded. Regular inspections and maintenance allow potential problems to be discovered early, before they cause other damage.Property maintenance companies and building owners can talk with manufacturers such as GAF to learn more about proper roof maintenance. Click here to get started.4. Warranty/GuaranteeA good warranty or guarantee program is one of the top reasons commercial building owners may choose a particular roofing system. Building owners want to know that they can count on the manufacturer to address any covered issues that may arise. Many roofing manufacturers offer warranties or guarantees for building owners that have no dollar limit on covered repair expenses.GAF offers several commercial roof system guarantees and warranties, ranging from 12 to 35 years of coverage, depending on the particular type of roofing system installed, how it is installed, and by whom. The Diamond Pledge NDL Roof Guarantee offers strong protection for commercial roofs—and for certain eligible systems, the coverage period can be extended by contracting with a GAF certified contractor* to provide maintenance throughout the roof's life. Additional requirements apply, see gaf.com for details.With proper maintenance, the right roofing system can provide protection for years to come.*Contractors enrolled in GAF certification programs are not employees or agents of GAF, and GAF does not control or otherwise supervise these independent businesses. Contractors may have agreed that they will use GAF roofing products, and may receive benefits, such as loyalty rewards points and discounts on marketing tools from GAF for participating in the program

Construction planning through to completion can be tricky to coordinate, especially within an urban area, which can present a range of complications. Building proximity, tall building heights, complex building structures, and densely populated areas are just a few challenges that can make it particularly difficult to consider traditionally heavy or large-sized materials when roofing or re-roofing a building.In addition to construction planning constraints, states such as California, New York, and others are adopting more stringent building codes to help alleviate the effect of urban heat islands.As property owners, architects, specifiers, and contractors are seeking new solutions to overcome these issues, the roofing materials industry is seeing increasing adoption of coatings and liquid membrane products that are easy to deliver and apply to the roof, while generating potential labor and installation savings during construction plus lower material costs for long-term maintenance.Benefits of Coatings for Urban ProjectsCoatings offer a distinct advantage in urban construction environments due in part to their mobility, ease of application, and potentially low environmental impact. At an average weight of 60 lbs. (27.2 kg) per 5-gallon (18.9 L) pail that can be carried by a handle, coatings solutions can ease transportation in ways that traditional roofing materials may not. Thanks to service elevators, coatings' advantages are often seen in busy metropolitan areas where using a crane or halting traffic may be expensive or otherwise challenging.Coatings also adhere to many existing roof materials, which can be helpful when restoring a structurally sound, low-slope roof that may have multiple surfaces, such as an asphaltic roof, a metal drip edge, and polyvinyl chloride (PVC) vent pipes.Coatings are manufactured to be "built on site," whether as just a coating with no reinforcement or through a layered approach, where fabric is embedded in the coating to create a reinforced liquid-applied membrane.The versatile application methods of liquid products and fabric rolls are a key benefit to urban construction projects. Many times, these products can be quickly and easily applied using brushes, rollers, or squeegees. These tools are relatively lightweight and easy to transport, and they don't require power or specialized equipment that may not travel well or can be disruptive to residents and neighbors — making them ideal for city construction in tight, crowded spaces.Additionally, with the build-on-site capability of liquid membranes and a lightweight fabric, it's possible to optimize a roof system to match any space. Liquid-applied products can seamlessly adhere to angles, making them an ideal solution for a roof with many details that need to be flashed or angles where a custom fit is needed, conforming to any detail to provide waterproofing protection.Coatings are also useful in maintaining and repairing roofs, which makes them a viable option for building owners and facility managers looking for a roof that can be easily maintained with similar materials to ensure proper adhesion and extend performance.Liquid-applied products can also meet the requirements of a more sustainable and environmentally conscious roofing solution. They may have the ability to restore a structurally sound roof without the need to tear off the existing roof. Additionally, many coatings are manufactured to comply with regulatory requirements, such as low volatile organic compounds (VOC) content, low or no biocides, or being zinc free (always make sure to check local building codes for applicable requirements).Types of Coatings for Urban ProjectsThere are many different technologies when it comes to roof coatings, and each has a unique advantage and offers a unique solution, depending on the needs of a project.Items to consider when selecting a coatings technology often include regulatory requirements and local VOC restrictions, weather conditions affecting the roof, the amount of foot traffic on the roof, and a range of other factors that may be unique to the roof.As with any project, it is important to ensure that each product meets or exceeds testing and certification requirements when selecting any coatings solutions, including the following:• Acrylic coatings are water-borne, typically have low VOCs and low odor, and can easily be applied or recoated in the future. Most acrylics are one-part products, meaning they are ready to use, and there is no need for mixing multiple components. Typically applied via brush, roller, or sprayer, acrylic coatings also offer easy cleanup.• Fluoropolymer (polyvinylidene difluoride, or PVDF) technology is a water-borne technology manufactured using Kynar Aquatec resin, which is based on Kynar 500 technology. The technology provides color stability, a strong solar reflectivity of lighter color coatings, and architectural or aesthetic value. This product is typically used only as a topcoat (over an acrylic basecoat) and on roofs where aesthetics are a primary concern.• Silicone coatings are moisture cured, have low odor, and can be applied easily. Offering a wide range of solutions to many roofs, silicone coatings are generally chosen for their high solids content. In particular, customers choose high-solids silicone coatings because they are suitable for roofs that pond water.• Urethane coatings, both single-component (1K) and two-component (2K), are solvent-borne, high-solids technologies that provide an excellent balance of tensile strength, elongation, and hardness. The 2K urethane products are specifically chosen when durability, dirt and mildew resistance, chemical resistance, weatherproofing, and high abrasion and impact resistance are needed.Combating Urban Heat IslandsThe urban heat island effect can best be described as what happens to urban areas as populations move into a central area — more pavement, fewer trees, more infrastructure, and more hardscape. There are many studies on the effects of urban heat islands, and while hard surfaces such as pavement play a large role, so do roof surfaces. This dynamic leads to higher temperatures in these areas, whereas their surrounding rural landscapes, which often have less pavement, more trees, and less infrastructure, typically see lower temperatures.To help mitigate this effect, coating roofs (and pavement) with lighter, more reflective colors will help lower roof temperatures.By coating an asphaltic roof with a white acrylic coating, one can greatly reduce the surface temperature. According to a 2010 article entitled, "Potential Benefits of Cool Roofs on Commercial Buildings," that reduction may be as much as 55 °F (30.6 °C) and may also result in significant savings in cooling energy. Cooling of the roof not only benefits the building owner but can also reduce the heat island effect in the area.ConclusionsWhether your need is easy delivery to an urban roof project, a creative roof design that will protect the building and provide a seamless detail, or a reflective roof solution to mitigate urban heat island effects, coatings and liquid membranes are a viable solution for you. With many different coatings technologies and manufacturers on the market, the decision can be challenging. To assist with your decision, ensure that you partner with a manufacturer who offers many solutions so you can find the one that is best suited for your project.To explore liquid-applied coatings solutions offered by GAF, click here.