Roof maintenance is necessary to protect your building and investment. An important component of roofing management strategy is regular roofing replacement. Even with a plan, unexpected problems often arise. You may have an 8- or a 10-year-old roof that starts leaking but you do not have it on the budget for a replacement for several years. And, what if rising costs for heating and cooling have become a more important consideration?
Making Roof Coatings Work
In both cases, a roof coating might be a better solution. So long as the existing roofing system is a good candidate for a roof coating, an appropriate coating is used, and workers install the coating properly, this may be your best bet. Evaluating roof coatings is similar to evaluating replacement roofs. Building managers need to fully research types of coatings and carefully choose the most appropriate product. Not all roof coatings are compatible with all roofing products. For this reason, it is important to understand roof coating options and application requirements, so you can avoid the most common problems that are sure to cost you unnecessary time and money.
Determine a Purpose
The first question to consider is what purpose the roof coating is going to serve. If the primary purpose is to provide limited solar protection for the roof surface or to increase the service life of the existing roof, there are many product choices. However, if the primary purpose is to provide maximum solar protection you will need a highly reflective white roof coating and the choices are somewhat limited. If waterproofing and or leak repair is also a goal, then a monolithic waterproof coating, such as a urethane or a combination of products, is a more appropriate selection. Finally, if the primary purpose is to save energy or better comply with energy codes, a highly reflective surface is essential. You can add a sprayed polyurethane foam (SPF) to the assembly to easily achieve this. Once you have established goals for the roofing project, you can further narrow down product choices by evaluating the existing roofing.
Select a Coating
The most common roof coating product categories are discussed below.
- ASPHALT COATINGS – You can choose asphalt cutbacks or emulsions. Cutbacks are bituminous products that have been thinned with a solvent to aid application. Aluminum pigments are added to the topcoats for reflectivity, while other modifiers can enhance strength, longevity, and thickness. Fiberglass fibers or strands can provide additional reinforcement. Asphalt emulsions are similar but use water as a carrier instead of solvents. Aluminum pigments added to asphalt cutbacks and emulsions give coatings solar reflectance index (SRI) values of 21-30 on a scale of 0-100.
- ACRYLIC ELASTOMERS – These are new-generation coatings that have a highly reflective surface, with an SRI that is often greater than 100. Most highly reflective acrylic elastomers are white and can be installed over existing bituminous or non-bituminous roofing.
- POLYUREAS – These polymer-modified products are relatively new. Some are specified at similar application rates to acrylic elastomers, and others are specified at much thicker dry mil thicknesses, which is more similar to urethane coatings.
- URETHANES – These polymer-modified products are most commonly installed on concrete substrates, such as parking decks or on wood substrates. Urethanes typically are not applied over other roofing products.
- SPF – This product is really an insulating system. This roofing is a spray-applied foam that forms to any roof curb or penetration and provides insulating value. The surface of SPF insulation typically is coated with urethane for protection and waterproofing.
Surfaces and Systems
Roof coatings were initially developed for application over bituminous roofing products. These roof types are excellent candidates for a roof coating, provided the surface is smooth and accessible. Gravel surfacing is extremely difficult to coat but can be done. The age of a bituminous roofing system also is important because aged membranes often have surface degradation that will need to be fixed before the coating can be applied. Ethylene propylene diene monomer (EPDM) roofing also can be coated, but there are limits to product choices here. Workers can apply acrylic polymers and urethanes but it is recommended that managers check with the manufacturer of existing EPDM roofing for compatible coating products. Other types of single-ply roofing, such as PVC, are unlikely to benefit from coating applications as most of them have integrated solar protection and reflectivity. Finally, concrete roof decks are great candidates for roof coatings. A number of polymers and epoxy products are available for this, but urethane coatings are the most cost-effective method to use.
Pitfalls to Avoid
There are common problems with roof-coating applications mostly associated with climate. The top 10 pitfalls that building managers must avoid in coating applications are discussed below.
- Poor product choice – It is important to research coating options and choose the one best for your needs. The wrong choice can result in more expenses and wasted time.
- The expectation of leak repair – Many coatings provide solar protection but not monolithic waterproofing. Some coatings manufacturers even advise that their products are not designed to seal leaks, and they recommend repairs before application.
- Blisters – Blistering arises from the presence of moisture under the coating. A roof that has leaked extensively might have moisture trapped, so before applying a coating, workers should make sure the roof surface is dry.
- Delamination – Delamination results from moisture, dirt or other contaminants on the existing roof surface. Be sure to scrape loose material from existing coatings and prepare the surface according to manufacturer recommendations.
- Pinholes, skips, and holidays – A complete, monolithic and continuous surface can ensure proper coating performance, so it is essential to avoid these problems related to inconsistent application.
- Too high or too low temperature – Applying a coating during the hottest day or the coldest day can cause problems with cure times and harm the quality of the finished product. Most manufacturers establish minimum and maximum ambient temperatures for application and these need to be adhered to.
- Improper mixing or application – Mixed on-site, these systems have a pot life, and it might range from minutes to hours. Should workers exceed this time, they should discard the coating.
- Inadequate surface cleaning – To provide a reflective surface that will save energy after a coating application, workers must keep it clean. Soiled surfaces can negate any energy savings a reflective coating can provide.
- Infrequent reapplication – Many coatings have recommended service lives of only five years and must be reapplied in order to continue working as needed.
- Disregarding manufacturer recommendations – Always follow manufacturer requirements regarding moisture, leak repairs, primers, surface preparation, application temperatures, mixing, cleaning, and service lives.
Before you decide on a roof coating option, consult with a professional roofing contractor and read manufacturer guidelines. For the best practices for all coating applications, call us today.