Metal roof coatings serve several purposes. Some of the main purposes of a coating are to protect the roofing system from moisture, heat and solar radiation. Coatings can also be used to restore aging or failing metal roofing systems. Different coating products can offer a combination of features to meet individual roofing needs.
The key feature of any coating is to protect the building from moisture penetration. The type of moisture and slope of the roof must be considered to select the right coating materials. If ponding is a problem, coal tar based coatings have a thickness that can increase slopes and resist penetration from standing water. Acrylics do not perform as well under standing water conditions.
The elastomeric properties of metal roof coatings can also be a critical feature. This defines the ability of the product to expand and contract with temperature changes. Under extreme temperature changes, a rigid roof coating could crack and then begin to leak.
Coatings with elastic properties can still provide a hard surface that is tear and cut resistant. Polyurethane sealants can also be applied for metal roof repair that offer superior weather resistance and permanent flexibility.
Reflecting heat and adding energy efficiency
White or aluminum based coatings help reflect sunlight, providing a cooler roof surface. Ceramic coatings also deflect heat, and reflect between 75 to 85 percent of the solar radiation that hits the surface. The solar reflective property not only reflects radiation, the coating improves the roof as it warms.
Excess temperature changes cause expansion and contraction in metal roofs, stressing the joints. Solar reflective coatings limit these temperature changes and should be used in areas with extremely high summer temperatures. However, in colder climates, or for roofs in continual shade, reflectivity may not be a major factor in choosing a coating.
In some situations, choosing a coating material with chemical resistance will be beneficial. Coatings containing silicones, coal tar, polyurethanes and polyureas are more resistant to chemical issues. Primers can also improve resistance, applying a primer with a rust preventative feature can greatly improve the longevity of the entire metal roofing system.
In addition to waterproofing, protecting and providing energy efficiency, some metal roof coatings are also manufactured to meet fire resistance ratings. While the metal roof itself resists fire, in some areas the coating material should also be taken into consideration for Class A requirements.
Discuss your roofing needs with a professional to determine the best metal roof coating for your unique application. Remember to consider if foot traffic is frequent and what other benefits you may desire including light reflection or increased energy efficiency.