Extending the life of a mod-bit roof

Energizer BK full fabric 5
Asphaltic-based reinforced systems offer potential for a long-term restoration solution, with warranties as long as 15 years.

Types of systems available
Eventually, the roof will reach the end of its warranted service life and show signs of aging, but not necessarily any of the aforementioned symptoms of severe conditions. In these instances, there are various products available that offer a wide level of performance. For simplicity, they can be classified into ‘restoration’ and ‘coating’ categories.

For severely aged mod-bit systems, employing a restoration system may provide the most sustainable option. Restoration systems typically include an asphaltic-based fluid or hot-applied system. The fluid-applied options can be water- or solvent-based; in high-performance systems, they can be 100 per cent solid chemistry. In all cases, the asphaltic system is applied to a clean and debris-free surface at the application rate recommended by the manufacturer.

In most instances, the product is heavier-bodied in nature and is applied with a slotted squeegee, roller, or spray unit. Still, it is normally self-levelling and works to fill existing voids and cracking. In the case of hot-applied systems, an asphalt kettle is utilized to preheat the asphalt or modified asphalt applied to the cleaned surface.2 In some cases, a primer is required with either liquid or hot applied systems. It is important to always consult the manufacturer’s recommendations before use.

The asphalt restoration is used to replace the lost waterproofing of the existing modified bitumen system. It serves not only as an additional layer of protection for the existing assembly, but also as a level platform for the subsequent application of additional system products.

In many applications of restoration systems, reinforcement is employed as part of the application. Polyester or glass mats are layered into the restoration product prior to cure. The reinforcement becomes part of the system and provides increased split- and puncture-resistance. Once cured, the restoration application is typically coated with a reflective coating. In some cases, while the applied system is still uncured, minerals or aggregate can be broadcast into the liquid restoration. The restoration ultimately sets and the aggregate becomes part of the wearing surface.

White-Knight Plus_over EPDM_Gould_2814
Many elastomeric coatings can be reinforced to provide a tougher, more durable solution for modified bitumen (mod-bit) roofs.

In situations where the mod-bit system is in good or better condition, a coating may instead be the best course of action. Coatings, like restoration systems, need to be applied to clean and debris-free surfaces. Available in wide varieties, they can be defined by their solution media (i.e. solvent- or water-based), their polymer type (i.e. urethane, acrylics, or thermoplastic), or their pigment (white coatings typically employ titanium dioxide as a pigment, while metallic coatings normally use aluminum flake). In many cases, primers are used on prepared surfaces first.

When selecting a coating it is important to consider the substrate over which the coating is applied—not all coatings can be used over all substrates. Further, the finished coat’s desired reflectivity must be taken into account. While white reflective coatings can be used to reduce energy used in cooling a facility, it may not provide annual energy savings because of the higher heating demand in northern climates like those found in Canada.

The environment in which the coating is being used must also be considered. For example, will there be chemical exposure or foot traffic? In some coating systems, a reinforcement can be used to create a more durable and long-term solution. As with restorations, the reinforcement is applied during the application process and, once cured, becomes an integral part of the system.

Working with a trained roofing professional or manufacturer is a great first step in deciding the best course of action. Selecting the right system for the roof top conditions is critical to creating the best sustainable solution.

Best practices in performing the restoration
As discussed in this article, the best practices for extending the life of a modified bitumen roof include:

  • ensuring the system is suitable for restoration;
  • proceeding with any significant repairs, such as removing wet insulation and fixing any splits or damaged flashings;
  • considering whether a restoration system or a coating is the best solution;
  • accounting for any specific conditions or performance properties necessary for success (e.g. need for a reflective system, or resistance properties against chemicals or abrasion);
  • preparing the roof system for application of the selected system;
  • following the manufacturer recommendations on application and preparation;
  • working with a qualified contractor or installer; and
  • following all manufacturer recommendations for use and ongoing maintenance.

Additionally, there is an extra ‘bullet point:’ stay in front of any issues. Performing frequent roof inspections is a key component to the long-term performance of the existing system and subsequently applied restorations or coatings. Keeping drains clear and repairing flashing splits and leaks is paramount in guaranteeing success. The best coating or restoration in the world cannot repair long-term neglect.

Charbel Boulos HeadshotCharbel Boulos, P.Eng., is president of Garland Canada, and has the knowledge and technical expertise to solve a variety of complex roofing and building envelope concerns. A licensed professional engineer, he has 25 years of experience in all facets of roofing design and construction, including hot asphalt, modified bitumen, cold process, and sustainable roofing. Boulos studied engineering at the University of Toronto, specializing in chemical processes and petroleum-based products, and received his professional engineering designation and license in 1990. He can be contacted via e-mail at cboulos@garlandind.com.

Joe Mellott Head ShotJoe Mellott holds multiple patents for roof-related innovations. He received the 2006 Industry Statesman Award from the Roof Coatings Manufacturers Association (RCMA) for his work in advancing roof coatings industry technology. A graduate of Case Western Reserve University, Mellott holds a degree in polymer engineering, is a frequent contributor of technical articles to industrial publications, and has participated in innumerable roofing- and polymer-related organizations. He has served as the technical chair and president of the Roof Coatings Manufacturers Association (RCMA), as well as sat on the board of the Cool Roofs Rating Council (CRRC). Mellott is the vice-president/general manager of the Innovative Metal Company (IMETCO) for the Garland Industries of Cleveland. He can be reached at jmellott@garlandind.com.

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