How to Improve Dirt-Pickup Resistance for Silicone Roof Coatings

By Abby Feinstein on November 7th, 2022

There are many reasons roof restoration and coatings have gained market share over the years, with silicone-based products at the helm of the growth curve. One of these benefits is silicone’s high solar reflectivity, which is a major consideration for roofing in California and increasingly so in other parts of the country.

But while silicone, like our SMARTCOAT 450 High Solids Silicone Coating, goes down bright white, one of the limitations to the product is its dirt retention. Within a few weeks, depending on environmental conditions, a silicone roof surface can be covered with a film of dirt and debris. Not only is this unsightly on buildings with rooftop visibility, but it also reduces that valued reflectivity.

Minimize Dirt Pickup with Surface Granulation

One way to improve the dirt-pickup resistance of silicone is to granulate the surface. In addition to dirt-pickup resistance, granulation adds strength, improved water wicking, and delivers a beautiful, uniform aesthetic. Silicone is also slippery, especially when wet; granulation mitigates that hazard.  

SMARTCOAT 450 is a 100% silicone-based, solvent free, single-part roof coating that may be used to re-coat existing silicone and acrylic roof coatings. It boasts impressive temperature adaptability, ponded water resistance, vapor permeability, and more. Like all SMARTCOAT 400 Series Coatings, it delivers excellent bond strength to all types of roof substrates without the need for primer, making it a popular, easy-to-use, time-saving solution. To take full advantage of these benefits and ensure that its high solar reflectivity lasts for years to come, we recommend broadcasting roofing granules as a final step after applying the coating.

Granulating Your Silicone Membrane

Depending on the specification and slope, many silicone membranes are applied in a single pass. When granulating, we specify a two-pass application:

• Apply the second layer in a contrasting color to the first, such as light grey and white.
• Apply the second layer at approximately 1G per SQ.
• When possible, apply both passes on the same day. The first coat should be walkable in 3-4 hours on average. This reduces the chances of moisture or dirt on the first coat, and you can work your way off the roof more easily.

Immediately broadcast #11 ceramic roofing granules in the color of your choice into wet silicone to complete saturation or refusal.

Maintain High Reflectivity for Long-Term Energy Savings

Keeping a silicone coating bright white and dirt-free can amount to significant energy savings over time. To ensure your roof coating will remain reflective for the long run, choose a system with high reflectivity as well as dirt-pickup resistance.