Roof Coating Systems—What They Are and How to Calculate Just What You Need

By Dawn Killough 05-11-2021
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Even structurally sound roofs may show the effects of weathering and UV damage. Roof coating systems can help protect and extend the life of existing roofing systems.

What kinds of roof coatings should you consider for your roof? And, just as importantly, how do you know how much coating you need for your roof?

Types of Roof Coatings

GAF offers a variety of roof coating systems made with acrylic, silicone, and polyurethane. Below are the key features of each type of system.

  • Acrylic coatings are an ideal solution for structurally sound roofs in need of restoration. Products such as GAF's RoofMate coating can be used on a variety of substrates to help protect the substrate against weathering and UV damage. Additionally, some acrylic coatings systems are fabric-reinforced for an extra layer of protection.
  • Silicone coatings, like GAF's line of Unisil silicone coatings, help protect the substrate against weathering and UV damage while also providing protection against leaks due to ponding water. Silicone coatings provide strong adhesion to many substrates, and come in both high solid and low solid varieties.
  • Polyurethane coatings, like GAF's line of Elastuff coatings, provide an excellent balance of tensile strength, elongation, and hardness. Their hard finish makes them well-suited for installations that require high abrasion, impact, and chemical resistance.

Calculating How Much Coating You Need

The amount of coating a project calls for will depend on a number of factors, including the type of coating, the size of the roof, the substrate being coated, the specific needs of the building, the goals of the owner, and the desired warranty or guarantee coverage. Installers can refer to GAF's Quick Specs and GAF's Application & Specifications Manuals to determine the number of coats and the dry film thickness required to meet the desired warranty or guarantee term. The application manual is also a great reference to identify proper substrate preparation and application techniques.

GAF has a new resource to help contractors, building owners, and distributors estimate the amount of coating needed for a particular project. According to GAF Product Marketing Manager Dave Rubin, the coverage calculator will help when "a contractor is out in the field or in their distributor's showroom and they need to quickly run a calculation."

The calculator is available to help estimate HydroStop acrylic membrane as well as Unisil silicone products. For Unisil silicone products, the calculator is located on the bottom of the individual product web pages. There's no sign-up required, and the tool is accessible from any device that has Internet, including mobile phones and tablets.

To calculate the amount of coating needed, follow the prompts in the tool. You'll need the following information:

  • Project name (optional)
  • Whether the project is located in Florida (and therefore subject to certain specific local code requirements)
  • Type of substrate
  • Square footage of roof to be covered
  • Linear feet of perimeter
  • Linear feet of curbs and penetrations
  • Parapet wall height in feet
  • Desired warranty period

With the information above, the tool can help estimate the amount of coating, fabric, and flashings needed for a project based on the information provided. The report can be saved as a PDF or printed for your records. (For privacy purposes, none of your project or contact information is stored in the system.)

The calculator provides plenty of additional help to assist customers with their calculations, Rubin says.

"We help guide you through the process and give you information about how to properly measure a roof, if you need some guidance on that," he says. "The menu takes you to our preparation guides that provide detail behind the proper prep work needed before you're ready to apply a roof coating—including if primers are needed, what type of primers are needed, and how to properly clean the roof."

It's important to note that the results provided by the calculator are an estimate of the required amount of coating. The accuracy of the estimate depends on the accuracy of the information entered and is for guidance purposes only. Always confirm quantities prior to ordering and ensure you are following local building code requirements.

Coating Calculations Made Easy

GAF aims to support commercial roof installers and building owners with a quick and easy estimate of how much material they'll need for their project. Installers will still need to reference the Quick Spec and application guides for specific information on substrate preparation, application instructions, coverage rates and required thickness and warranty or guarantee options—but Rubin says GAF hopes to give contractors more confidence in their calculations and make the process simpler.

ABOUT THE AUTHOR
Dawn Killough is a freelance writer in the construction, finance, and accounting fields. She is the author of an ebook about green building and writes for construction tech and green building websites. She lives in Salem, Oregon with her husband and four cats.
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