Managers need to choose roof coatings by considering a variety of factors before making the best decision.
For example:
Facility goals: Once the decision to use a roof coating is determined as a viable option, the next step is determining the goals of the facility. While there are several factors that contribute to the coating’s performance, one of the biggest is determining its expected duration. For long-term solutions — say 15 to 20 years — multiple coats are generally required. For a short-term solution of about five years, a single coat can usually prove sufficient.
“Always take into consideration what the best solution for the customer is,” says Kelly Linhares-Nelson, product marketing manager for the Liquid Applied Membranes (LAM) group of Sika Roofing. “Know the expectations for performance, the economic situation and the type of technology needed to choose the correct roof coating that is most suitable. And most of all, know the quality of the product you are getting. Not all coatings are created equal. Does the manufacturer you are choosing have a quality-control program?”
Other things to consider include the life expectancy of a roof re-cover.
“Do you want a warranty, and if so what kind, full or limited, and for how many years?” says Linhares-Nelson. “What kind of maintenance is needed and expected, and do you want to be able to do the work inhouse?”
Roof condition: Every roof re-cover must have a moisture scan.
“All wet areas would need to be removed and replaced before any recover application,” Linhares-Nelson says. “It needs to be determined what the substrate is, are there any compatibility issues, and is this a suitable project for a liquid roof coat?”
Budget restrictions: In many cases, the lowest cost and level of disruption option is repairing the existing roof system. Next is restoring or coating it, followed by recovering it with a new roof. The highest cost and level of disruption option is a full tear-off and installation of a new roof system.
“Any time you can repair or restore an existing roof system and extend its useful life, you are reducing the waste to a landfill, making the system more sustainable and lowering the life cycle costs of the roof asset,” Vross says.
Some systems use locally reinforced waterproofing coatings as a maintenance coating or re-cover of existing roofs. This type of reroofing can be much more budget-friendly than a complete roof tear-off and replacement.
Budget restraints and improvement projects are factors in deciding whether to go with a new roof or a coating system. If the roof is mechanically unsound, “you need to consider a new roof. However, if there are minimal leaks that can repaired with a coating system, that’s when one should be considered,” McGuinness says. “The cost of a new roof would be much more expensive than applying a coating. Plus, the coating saves on maintenance/repair costs because it repairs the existing leaks and prevents leaks in the future.”
If a coating system is used every few years, it can extend the life of the roof for decades.
“The coating becomes the sacrificial coating. Acrylic coatings will wear/erode half a mil (a unit of length equal to one thousandth of an inch) each year,” McGuinness says. “Therefore, if you put a 20-mil coating on every 10 years the roof can last for decades.”
Types of coatings: There are many coating options, such as acrylic-, urethane-, SEBS- and silicone-based. Each system has its benefits and weaknesses, and coating types will vary for all building types, climates and more. Some important attributes to look for in a coating are elongation, weathering, reflectivity and the proper dry mil thickness. Multiple layers of coatings provide a stronger, better and more redundant approach to the restoration versus one single, thick layer.
Reinforcement plus coating: In addition to a coating, a reinforcement sheet such as polyester should be applied during the restoration. Without it, the coating can crack or split, with the existing substrate failing. The reinforcement sheet prevents this by adding the proper tensile strength to the restoration.
All penetrations and perimeters should also be reinforced with a minimum of three courses consisting of a reinforcement sheet such as polyester and a quality elastomeric roof cement.
Ponding water: If the roof has excessive ponding water, the situation should be dealt with by either adding additional slope or drains before a restoration or coating is applied.
Metal coatings: When restoring a metal roof, Vross says, it is important to not only address both the horizontal and vertical seams.
“It is difficult to visually inspect a vertical seam to identify if the sealant is properly applied or if the seam was crimped or attached properly,” he adds.
Addressing the vertical seams with seam tape eliminates directional wind-driven rain leaks that may occur even after the roof is coated. It is also a longer-term approach than using just a coating or caulking. With a metal roof it is also important to not only coat it but repair any defects such as deteriorated metal and foam closures at the edges.
Staffing challenges: While the waning labor force is an issue in every trade, skilled labor is hurting the most. Managers might consider single-component products that require little to no mixing and no measuring, Linhares-Nelson says.
“This makes them easy to use. Applicators should still be professionally trained for installing these products, but it does not require highly skilled personnel,” she says.
Howard Riell is a freelance writer from Henderson, Nevada.
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