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Shield metal roofs with acrylic to win the war against elements

Article-Shield metal roofs with acrylic to win the war against elements


Galvanized or factory-finished metal is the predominant roofing material used in self-storage construction, providing a low-cost, durable and easily maintained barrier from the elements.

Metals rigid surface makes it susceptible to damage. Changing temperatures cause significant expansion and contraction, putting pressure on joints and fasteners. Rain, snow and dew contribute to corrosion. Worse, high winds can rip a metal roof right off the building. Damaged roofs prompt financial losses and liability concerns for owners, yet roofs remain the most neglected aspect of self-storage.

When it comes to heat, nothings worse than the sun. Exposure to heat and ultraviolet rays plays havoc on a metal roof s lifespan. Galvanized and white factory-finished metals expand significantly when exposed to sunlight. Metal likes to absorb heat and hold it. A thin factory finish of 3 to 4 millimeters is typically not effective in preventing heat absorption.

As metal heats up, a phenomenon called thermal movement occurs, making the metal get bigger and expand in all directions. When the sun goes down, the roof cools and contracts; the process becomes more exaggerated in winter months, stressing joints. Over time, the expansion and contraction of the metal can loosen screws and seams, resulting in leaks.

Combat Zones

Joints and seams are where two or more sheets of metal meet and overlap, or where a section of the roof meets a vertical wall or dissimilar substrate. These areas are often caulked or crimped to help prevent leaks. As time passes, thermal movement can compromise the caulks adhesion and loosen the crimped seam, weakening it sufficiently to cause a leak. Areas of exposed metal are subject to oxidation upon exposure to moisture, resulting in rust. Moisture from rain or melting snow will inevitably find loose fasteners and damaged joints, a potential liability concern.

Once fasteners and joints are compromised, wind may cause further damage. High winds can catch the edge of a loose piece of sheet metal, transforming it into a sail. The more surface area turned up to the wind, the better its chances of becoming ripped completely off the building.

Although this may seem dramatic, it should make you question your metal roofs integrity. Fortunately, most manufacturers have engineered their products to minimize potential hazards and provide maximum performance. However, problems with corrosion and leaking eventually affect all metal roofs as they age.

Applying a high performance, elastomeric roof-coating system eliminates numerous concerns and extends the life of an aged metal roof. Sustainable roofing systems include accessories such as primers, reinforcement tapes, butter grades and roof-fastener seal caps.

Preventing Leaks

Butter grade or self-adhering caps permanently seal the entire fastener head to the surrounding substrate to prevent them from backing out. Either method is inexpensive and easily applied.

To prevent leaks in overlapped seams, they should be reinforced with non-woven polyester fabric or a self-adhering, polymer-backed tape. The polyester fabric is embedded into a strip-coat of basecoat, while the tape employs the same adhesive used on the fastener caps. Both products are available in several widths, and are flexible enough to conform to metal-roof joint contours.

Reinforcement is used at detail areas such as protrusions, drains, vents, scuppers, parapet walls and vertical or horizontal interfaces. Once dried, they can be treated with elastomeric roof coating to complete the system.

After the roof is thoroughly cleaned, necessary repairs have been completed and detail areas reinforced, its ready for one or more coats of a high-build basecoat, which promotes adhesion and builds thickness. Applying multiple layers creates a waterproof membrane with long-term performance.

Using 100 percent acrylic polymer components ensures the coating system will remain permanently flexible, allowing it to expand and contract, while bridging seams and joints without splitting or delaminating. The result is a monolithic, 100 percent-adhered membrane with no mechanical fasteners, screws, nails or adhesives.

Applying a white reflective topcoat is the final step. It should possess the same high-build, elastomeric properties as the basecoat, with additional weather-resistance properties. A white or light-colored finish bounces off 85 percent of the suns heat, allowing the metal to remain cooler and not expand as much. The highly elastic nature of the topcoat and basecoat enables it to stretch with underlying movement. The length of the warranty usually dictates how thick and how many layers of basecoat and topcoat are required.

A quality, liquid-applied roof coating system is an economical solution for virtually any type of low-slope or flat roof. Engineered to be waterproof and permanently flexible, it reduces energy by decreasing interior temperatures. 

Roof coatings are applied more thickly and offer much greater elasticity than traditional paint. Premium systems are covered by 5- to 20-year, non-prorated warranties that can be extended (with periodic recoats) to last as long as the building. This type of coating system is ideal for metal roofs susceptible to leaks at fasteners and seams, and panel corrosion. A fluid-applied, 100 percent acrylic program is also effective in creating a waterproof barrier on steep-sloped metal roofs.

Look for a premium-quality white roof coating system that meets U.S. Cool Roofing Product standards. It should also have independent fire-resistance credentials and be certified by the U.S. Environmental Protection Agencys Energy Star program as well as the Cool Roof Rating Council. In addition, some systems surpass state and federal approval as an energy-conserving product.

A Winning System

When it comes to energy savings, studies have proven a white reflective roof surface significantly lowers interior temperatures. The amount of electricity for air conditioning is reduced, resulting in significant cost savings, a major concern for property owners.

A cool roofing system offers environmental benefits. A reflective coating reduces the heat island effect, which contributes to the accumulation of atmospheric greenhouse gases. The result is increased carbon dioxide levels and, consequently, smog.

Bright-white roof coatings reflect the majority of the suns UV back into space and away from earth before it is absorbed. Some studies have shown that air temperatures in communities with predominantly black or dark-colored roofs are several degrees hotter than surrounding countryside, simply because streets and roof tops retain such a high percentage of the suns heat.

Metal roof systems must battle the elements every day. An acrylic coating system offers a shield. A longer lifespan for your roof means your self-storage facility is protected against leaks and liability concerns. The war is over; metal roofs win. 

Clint Whitsett is the marketing coordinator for United Coatings. Based in Spokane, Wash., the company has manufactured roofing systems for more than 80 years, offering a full line of premium quality protective coating for interior and exterior walls, pedestrian and vehicular traffic decks, and new or existing roofs. For more information, call 509.926.7143; visit

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