Time and environmental conditions can take a toll on building exteriors, fading and degrading once-vibrant finishes. One option for restoration is to replace the façade with new, factory-fresh materials — a costly endeavor requiring major, disruptive construction. Another option is to restore the surface with a standard latex paint — a cost-effective, but short-term, fix that can lead to ongoing maintenance and a compromised aesthetic. A third and better option is to specify section 09 96 00 high-performance field-applied coating systems for a long-term, cost-efficient and sustainable façade service life.
The right high-performance exterior coating can provide the same type of protection associated with factory-applied coatings. It also offers aesthetic advantages when custom-color-matched to align with branded or organizational color identities. For example, Solano Community College, located near San Francisco, recoated its Vallejo Center campus building with a polyvinylidene fluoride (PVDF)-based, high-performance, restoration coating — NeverFade with Kynar Aquatec — custom-mixed to match the college’s vibrant signature color, Solano Blue.
Solano Community College saved $48,000 by choosing long-lasting NeverFade Façade Restoration Coatings for its exterior restoration.
The specification process should consider several critical factors that can impact the effectiveness of the job as well as the performance and longevity of the coating system.
Sunlight, moisture, temperature extremes, wind, particulate, chemical pollutants and abrasion can drastically break down coating materials over time. Ultra-violet (UV) radiation is the most damaging of all environmental factors. Coupled with chemical agents, water and atmospheric pollution, UV radiation can react with a coating’s chemistry and pigment particles, attacking the chemical bonds of the coating’s binder resin.
The problem is more than just an aesthetic one. As coatings degrade and erode over time, they can take on a chalky consistency, which means they can be removed with even the lightest touch or rainfall. The coating will continue to erode, removing the exterior material’s important protective layer and exposing the substrate. The result? Chalking, corrosion (identified by rusting and pitting), mold and mildew growth and other problems that could lead to structural failure if not remedied.
To prevent this degradation, challenging ambient conditions must be identified and a coating system with the appropriate polymer chemistry must be chosen. For example, Kynar Aquatec resin, the backbone of NeverFade Façade Restoration Coatings, is a PVDF technology comprised of carbon-fluorine atoms — one of the strongest chemical bonds and impervious to harsh UV conditions.
The previous paint on the surface of this home in Sanibel Island, Florida, had degraded, becoming a food source for mold and algae to grow (left). After recoating with NeverFade, the home has been mold-free for nine years (right).
High-performance exterior coatings are specially formulated for compatibility with the surface or surfaces that need refinishing. A formulation developed for stucco or masonry will not likely be compatible with steel or aluminum surfaces, for example.
The Westin Tampa Waterfront Hotel was restored with a custom-colored NeverFade Original Topcoat on its brick surface and NeverFade Metal Restoration Topcoat for its window profiles.
The condition of the existing coating system will indicate whether complete removal of the old paint or recoating the painted surface is the best solution. The amount of corrosion or degradation present, the number of defects on the surface, the adhesion integrity and the type of existing coating on the substrate need to be considered before making an overcoat or complete-removal decision.
Customer-centric, high-performance coating manufacturers will assist with a pre-job inspection of the property and craft a project-specific CSI SectionFormat specification for surface preparation and coating system application. They will also provide technical data sheets, safety data sheets (SDS) and field application guides, all of which should be consulted. These documents will provide important information about how to prepare the substrate and properly apply the coating system. Keep in mind, some projects and substrates may require more preparation than others.
In general, coatings should be tested on the substrate using the ASTM D3359 Standard Test Method for Measuring Adhesion by Tape Test to verify that the coating has adhered properly to the surface.
COATING SYSTEMS: RESTORING, NOT JUST PAINTING
The vast majority of coating system failures can be traced to poor surface preparation. Newly applied substrate materials, such as concrete, masonry and plaster, should cure for at least 30 days before coating them, while the pH of the material is monitored. This is an important project timeline consideration.
For steel, the amount and type of corrosion need to be evaluated and mitigated using proper SSPC or ISO standard practices for surface preparation prior to coating. Coatings isolate the substrate from the environment and form a barrier to protect against corrosion. Applying the coating uniformly and properly is critical, because a corrosion reaction can happen in an area smaller than a pinpoint.
A primer will provide an important bonding layer to help the topcoat adhere to the surface. Compatibility — or intercoat adhesion — between the primer and the topcoat is crucial. Poor intercoat adhesion can lead to delamination, inadequate abrasion resistance and other defects. For this reason, it is recommended that the two products come from a single manufacturer.
As discussed, selection of the right primer depends on the substrate and the environment. Involving the high-performance coating manufacturer during the pre-job conference and inspection will help the specifier select the right system for the job and avoid incompatibility issues.
Proper application techniques for the primer and topcoat must be followed in accordance with the coating manufacturer’s instructions. The coating system’s field application guide, product data sheets and specification will outline details such as coverage rates, dry time (to-touch and to recoat), pot life, reduction instructions as well as optimal ambient temperature and humidity conditions for application. Although it’s not always possible, application in direct sunlight should be avoided, as sunlight can affect the flow, leveling and application characteristics. High wind velocities can impact spray application, which can result in loss of materials, low film build, excessive dry spray or overspray. Be sure to work all these weather-related variables into the project timeline.
If the structure is normally exposed to dust and contaminants, the surface should be protected during the application and curing process. Dust and contaminants that settle on freshly applied coatings can impair the integrity of the coating, leading to a shorter coating life, possibility of surface defects and reduced performance.
The installation of a mockup on a small portion of the structure, prior to coating, will allow for adhesion testing and ensure that the aesthetic and color meet the client’s expectations.
PVDF-BASED COATING SYSTEMS
When preparing a specification, there are a range of popular exterior coating systems to consider — from latex, epoxies and polyurethanes to high-performance polysiloxanes and FEVE-based options to hybrids of these. Many in the architectural community, however, have turned to high-performance PVDF, a tough engineering thermoplastic with a proven record of performance in extreme conditions for more than 50 years. Its strong carbon-fluorine bonds allow the coating formulation to withstand thermal, chemical and ultraviolet conditions without degrading.
PVDF is innately hydrophobic and retains this property for an extended period. The hydrophobicity helps with water repellency and dirt resistance by providing a low surface tension for a self-cleaning effect. While coatings with other types of polymeric resins may have some initial hydrophobic qualities, this characteristic tends to diminish after exposure to the elements for a year or two.
PVDF also inherently resists mold and mildew growth, as there is no UV degradation or plasticizer migration creating a food source for bacterial growth. Because most PVDF-based coatings contain an acrylic component, fungicides are often incorporated to further resist mold growth, a prevalent problem in coastal areas or high-humidity environments.
The polymer chains of the PVDF are not compromised by UV, unlike traditional latex or urethane coatings. However, when other polymers are incorporated, it’s important to look for coating technologies with additional high-performance, UV-blocking additives and complex inorganic pigments to protect the substrate from the harmful effects of UV rays. This ensures long-lasting fade resistance and a barrier of protection between the substrate and its environment.
A LONGER LIFE
Incorporating section 09 96 00 into a project specification can heighten the expectations for coating performance across the architectural industry.
An eye-catching restoration of the Great Stupa of Dharmakaya in Colorado’s Shambhala Mountain Center features NeverFade Façade Restoration Coatings in 15 rich, custom-matched colors.
Selecting a truly compatible coating system and a licensed applicator certified by that system’s manufacturer is a great start. An experienced and approved applicator’s expertise in selecting the right coating system to match the structure’s substrate, prepare the surface properly, perfect the application and maintain environmental compliance with local regulations will help ensure long-term success of the project. Look for a coating system that offers a long-life guarantee and a manufacturer that is involved in each step of the coating process.