Liquid Applied Membranes vs Coatings

Written by Dave Waldron, StormCure

When liquid applied roofing is mentioned, thoughts for many within the roofing community and beyond immediately go to coatings.

However, in the world of liquid applied roofing, waterproofing, and surfacing, liquid applied membranes are a significant development revolutionizing the industry. Liquid applied membranes are “not a coating!”, which we will delve into further here.

Roof Coatings: Synopsis

Simply stated and defined, modern roof coatings are fluid-applied, high solids liquids typically used for roof maintenance or repair. Roof coatings are designed for protecting and extending the useful service life of roof assemblies for existing roof coverings, such as BUR, metal, modified bitumen, single ply membranes, and spray polyurethane foam. Roof coatings are often applied to low slope roofs on residential, commercial, and industrial buildings to extend the life of an existing roof.

The most common types of roof coatings are made from acrylic, silicone, polyurethane, or asphalt, each offering unique properties, and often applied by roller or spray. Generally, roof coatings are applied unreinforced or only partially reinforced and often thought of as the least costly option for roof remediation, but this may not always be true. So, what are the potential benefits of roof coatings? Roof coatings offer several benefits in lieu of roof replacements including the following:

• Weather Resistance: Roof coatings create a protective surface-level barrier against harsh weather conditions like UV rays, rain, snow, and wind, preventing deterioration of the underlying roofing materials.

• Extended Lifespan: By shielding the roof from the elements, roof coatings help extend its lifespan, reducing the need for frequent repairs or replacements.

• Energy Consumption Reduced: Reflective roof coatings can lower the amount of heat absorbed by the building, reducing reliance on air conditioning and energy costs.

• Improved Aesthetics: Some roof coatings can also improve the appearance of the roof, particularly after their initial installation.

Though once applied and fully cured roof coatings offer waterproofing characteristics, a roof coating is primarily a thin mil (often 20 – 40 mil total thickness) protective layer applied to the surface of an existing roof to extend its lifespan, enhance its durability, lower energy costs by reducing heat transfer, improve its resistance to weathering, and adds an additional measure of waterproofing.

That said, a roof coating often has limited adhesion (usually only required to be 2 lb/ lineal inch peel strength), depends on the existing roof assembly and membrane as its backbone for waterproof integrity, performance, and wind resistance The lack of full reinforcement throughout the coating also means the coating relies on its elongation alone, which are insufficient to offer crack bridging properties. When a defect, such as a small crack, appears in the substrate where previously there was none, this will eventually appear in the coating with cyclical movement, as an infinite percentage of elongation would be required to bridge the gap permanently.

Another significant factor regarding roof coatings is that most cure through a process of either moisture absorption (moisture-cure) or drying (evaporation of solvent or water) depending on the coating type. Silicone coatings typically cure by reacting with moisture in the air, while acrylic coatings cure as moisture evaporates. Therefore, the cure time for roof coatings is often measured in hours or days, leaving newly applied coatings subject to damage by rain and precipitation as well as being impacted by other factors like ambient temperature and humidity. The long cure times can also be exacerbated by the need for multiple coats to build mil thickness in many applications.

Bottom line, roof coatings are for roof maintenance and repair option only offering limited performance reflected in the limited “material only” warranties (free from manufacturing defects, rather than against leaks) warranties of 5 to 20 years issued by most roof coating manufacturers. So how do liquid applied membranes differ?

Liquid Applied Membranes

Liquid applied roof membranes (LAM) are a type of waterproofing system that involves applyinga polymer-based liquid resin with reinforcement, which cures to form a seamless, waterproofmembrane barrier. LAM’s are typically applied using one or two-component cold-applied flexiblepolyester, polyester methacrylate (PeMA), polymethyl methacrylate (PMMA), polyurethanes (PU),polyurea hybrid, and silane terminated polymer (STP) resin technologies reinforced with polyesterfleece fabric or fiberglass chopped strand mat for added strength.

Unlike roof coatings, LAM’s form cross-linked monolithic, seamless, fully adhered, and self-flashing polymer membranes typically applied at formidable mil thicknesses (60 mil and greater) often exceeding their factory produced single-ply roofing membrane counterparts.

The resulting LAM is watertight, durable, and reliable protective membrane barrier that can perform in the toughest environments. Beyond existing roof recovery, LAM’s may be used as waterproofing for new roofs, replacement roofs, roof re-cover systems, parking garages, plaza decks, balconies, and even interior spaces like mechanical rooms.

Finally, the superiority of LAM’s is underscored and backed by long-term labor, material, and no dollar limit (NDL) warranties of 20-25-years offered by most serious LAM manufacturers.

LAM’s are also aesthetically pleasing especially when using a fiberglass mat for a smooth and sleek finish, come in a variety of standard and custom colors giving designers options to blend with natural landscapes, architectural styles, landmark structures, or local regulations. A review of the many benefits and advantages of LAM’s include the following:

• Substantial Warranty Options: As mentioned above, LAM’s provide real long-term labor and material manufacturer warranties for existing roofing/waterproofing recovery or new construction applications. These warranties are more than just material alone, protecting against leaks occurring through the membrane.

• Rapid Curing & Reliable Application: Some LAM technologies, such as flexible polyester, PeMA and PMMA, offer rapid setting polymer resin-based systems that may be applied in a wide range of environmental conditions including extreme temperature and humidity. Rapid curing systems offer fast dry-in of the building typically being rainproof within 15 minutes and fully cured within 45 to 60 minutes after application.

• Complex Details Made Easy: LAM’s offer easy application for complex geometries and can conform to virtually any shape and profile, LAM’s conform to complicated flashing details and penetrations with ease, speed, without need for termination bars, fasteners, sealants and eliminating need for pitch pans/pockets or metal sleeves making them virtually maintenance free.

• Versatility: LAM They can be used on a variety of roof types, above and below grade waterproofing, interior waterproofing (i.e., mechanical rooms), traffic decks, balconies, and more.

• Substrate Compatibility: LAM’s provide exceptional adhesion to most common substrates including but not limited to concrete, masonry, wood, metals, single ply membranes (PVC, TPO, and EPDM) and bituminous roofing.

• Seamless: LAM’s eliminate seams which are common weaknesses in traditional roofing systems.

• Fully Adhered: LAM’s may be bonded directly to the substrate preventing lateral water migrationin the event of a puncture or storm damage.

• Durability: LAM’s are highly durable, resistant to standing or ponding water, UV radiation, most chemicals, and other environmental factors.

• Flexible Membranes: Flexible LAM’s are capable of handling normal building and thermal movement found in all buildings and structures.

• Reinforcement: LAM reinforcement enhances their strength, puncture resistance, and crackbridging ability. When using fiberglass mat to create a composite membrane, the toughness of the resulting LAM is enhanced even further and far beyond most alternative roofing and waterproofing membranes.

• Cost-Effective Waterproofing: LAM’s are an ideal solution for refurbishment or recover projects since they eliminate the need to tear off the existing leaking/failing roofing and waterproofing systems. This saves on costs associated with a tear-off such as labor and disposal.

• Sustainability: LAM’S offer sustainable benefits such as improved energy efficiency and reduced heat island effects. Roof recovers, when permitted by building code regulations and project conditions, can result in significant monetary savings to the building owner and reduction in landfill waste.

• No Building Disruption: LAM’s typically use hand-tools to install, eliminating many concerns including fire and disruptions to building occupants. LAM’s are ideal for urban spaces that restrict the use of hot asphalt, torches, or heat welding.

  
  

Simple Summary

A liquid-applied membrane (LAM) protects the integrity of the building like traditional membraneroofing systems. Whereas coatings are designed for extending the life of structurally sound andwatertight roofs.

The International Building Code allows options for both coatings and liquid applied membranes inroof maintenance and repair applications, and liquid applied membranes (LAM’s) for low andsteep slope roof covers, so undoubtedly there is a place for both in roofing and waterproofingapplications. That said, LAM’s offer the greatest versatility, meet established performance standards demanded by building codes including minimum physical properties, wind uplift resistance, and fire resistance, as well as offering the best return on investment for owners by resetting the “roofing clock”.

For further information on coatings, a good resource is The Roof Coating ManufacturersAssociation (RCMA). To find out more about liquid applied membranes, feel free to contact STORMCURE.

The opinions expressed are not necessarily the views or opinions of NTRCA, its board of directors, or its members. The information provided does not constitute legal advice but rather are opinions to help you and your attorney make the best possible decision for your company. Please note that the opinions may not reflect how the law may be enforced or interpreted in the future.