Technical Articles

Applying The Right Roof Restoration Coating To The Right Roof

By Tom Stuewe, The Garland Company, Inc.

In today’s building industry and economy, we all want to get the most value out of what we purchase. Therefore, when you make a large investment like a roof, it becomes critically important to protect the investment through proper maintenance to ensure you will get the longest possible life out of your roof system.

Due to increased labor costs and the environmental considerations of a roof tear-off, roof coatings and roof restoration systems are becoming a more popular option. According to the ChemQuest Group, the market for polymer-based roof coatings is estimated to be $500-$550 million, with white cool roof coatings accounting for nearly a third of this amount. With an annual growth rate of over 4% per year, roof coatings are outpacing most other conventional roofing products. Of course, before you consider which restoration solution is the most appropriate option, it’s important to assess the current state of your roof.

Get To Know Your Roof

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Cool roof coatings reduce energy bills by decreasing air conditioning needs and help extend the life of roof systems.
 

Knowing when to repair versus when to replace a roof is a critical decision that requires an expert eye. Trained roofing professionals can assist you in by providing visual inspections to help identify roof damage and leaks, which are most often found in flashings and roof penetrations. Address these critical areas prior to applying any roof coating. Core cuts and non-destructive testing provide key information in determining the condition of your roof. Also, wet insulation on a roof will need to be removed and replaced before the roof can be restored. An infrared scan can identify locations of wet insulation and typically if more than 30 percent of the roof’s insulation is wet, a complete tear-off is recommended.

Selecting The Right Roof Coating

With so many different types of products and chemistries available, it is important to select the most appropriate product based on your environment and needs. Some important roof conditions to consider when selecting a restoration coating include:

• Current condition of the roof

• Location

• Slope

• Ponding water

• Chemical exposure

• High heat exposure

• UV exposure

Subjecting a roof or restoration coating to any or all of these conditions will greatly affect its performance and life expectancy. Therefore, when selecting from the variety of roof coatings available in the market today, it is important to consider the features and benefits of each coating type, as well as its drawbacks.

Acrylic Roof Coatings

Acrylic coatings are very common in the roofing market today because they are typically water-based products and are cost effective. Water-based acrylic roof coatings are both easy to use and environmentally friendly. Acrylic coatings are most often used for reflectivity, and they are designed to cool the roof down. The net effect is reduced energy costs as well as protecting the roof surface from UV exposure. Acrylic coatings are also typically very elastomeric, allowing for fluctuations in temperature without affecting the actual coating. However, they typically do not have a high tensile strength, and this can affect the coatings ability to resist wear and tear making the roof restoration or coating more susceptible to damage from ponding water. In general, acrylic coatings help reduce cooling costs at a more economical value, while at the same time increasing the service life of your roof surface by protecting it from UV exposure.

Polyurethane Roof Coatings

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Polyurethane high tensile restoration of a 20 year old roof.
 

Polyurethane coatings becoming more common in the roofing market today because they provide a highly durable surface that protects the roofing system from a wide variety of conditions. Urethanes typically have higher tensile strength when compared to most other coatings, allowing the coating to resist expansion and contraction of the roof system. This can be very important in high stress areas, around penetrations, or on wall flashings where your building endures the most abuse.

Good roof practice recommends no ponding water. However, small bird baths are typical on most low slope roofs. Urethanes will provide better protection in bird bath areas. Since roofs tend to fail first in areas prone to ponding water, selecting a urethane coating (in addition to creating positive drainage) is a good choice when this condition is present.

It’s important to note that polyurethane coatings are broken down into two main categories: aromatic and aliphatic urethane formulations. Aromatic urethanes can be a more cost effective choice for your roof restoration while still providing the core benefits of a urethane coating. One downside of the aromatic urethanes is that they will chalk and/or yellow due to UV exposure which could affect the integrity of the film over time. Aliphatic urethanes will not chalk or degrade in UV light, allowing them to maintain their appearance as well as their film integrity. They provide long-term protection from UV exposure as well as protection from other conditions.

Silicone Roof Coatings

Silicone coatings have been in the industry for a long time and are mostly used to cover and protect spray polyurethane foam (SPF) roofs due to the coatings permeability. Silicones are also very well suited for areas with extreme temperature ranges and where UV exposure is more frequent. Silicone coatings provide a slick surface and once applied, only another layer of silicone coating can be applied as the recoat. One drawback is high dirt pickup of these types of coatings. Therefore, they would not be ideal in highly visible areas where aesthetics are required. Also silicone coatings have very low abrasion resistance so they are not the ideal coating for areas of high traffic.

PVDF Roof Coatings

Another type of roof coating that is gaining market acceptance is a Kynar® polyvinylidene fluoride (PVDF)-based coating. Kynar based coatings have long been used in metal roof applications, and they are now being used in traditional low-slope roof coatings. PVDF-based coatings are typically water-based products and their main purpose is to resist dirt pickup and maintain high reflectivity. Due to the PVDF resin used in this type of coating, it will maintain its reflectivity for very long periods of time without fading or yellowing like many other coatings. According to Arkema – the manufacturer of the Kynar® PVDF resin - “Many years of outdoor exposure in direct sunlight have little effect on the physical properties of Kynar PVDF.” The dried film surface is very smooth which provides resistance to dirt pickup, allowing the roof to get the maximum reflectivity benefit possible. These benefits make this type of coating ideal for roofs that are highly aesthetic and need to maintain high reflectivity.

Know Your Roof Coatings

   Performance Of Roof Coatings
Condition Polyurethane Acrylic Silicone PVDF
Ponding Water Best Acceptable Better Good
Chemical Exposure Best Acceptable Good Better
High Heat Exposure Better Acceptable Best Good
Building Movement Best Better Good Acceptable
UV Exposure Better Good Good Best
         

As you can see, there are many different types of coatings you can select from for your roof restoration. When selecting a coating to restore your roof, make sure that the coating is designed for the conditions of your particular roof. Each of these coatings has its own strengths and specific advantages that make it suitable for certain roof conditions. Selecting the right coating will ensure the restoration provides long-term protection to your roof system. Maintaining your roofing asset will provide you with the highest return on your investment.

The author, Tom Stuewe, is an eleven year veteran of the construction industry and active in many construction and coating industry associations. Stuewe is the Coatings & Mastics Product Manager at The Garland Company, Inc. a 100+ year old manufacturer of high-performance solutions for the total building envelope.

About Garland

Garland logoThe Garland Company Inc. is one of the worldwide leaders of quality, high-performance roofing and building envelope solutions for the commercial, industrial and institutional markets. For over 120 years, Garland has continually developed unique product and service offerings that have raised the bar of performance while exceeding the individual needs of customers throughout the world. Today, Garland's network of over 200 local building envelope professionals is strategically positioned throughout the United States, Canada and the United Kingdom to provide quality building envelope solutions for single and multi-property facilities. The Garland Company Inc., headquartered in Cleveland, Ohio, is an ISO 9001:2008 certified company. For more information about Garland, visit www.garlandco.com or call 800-321-9336 to be connected with a local Garland representative.

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