Silicone roof coatings
Silicones are moisture cured and humidity can even promote their cure. In some applications, the use of silicone can eliminate the need for a primer.
Strengths: Silicones weather better than other coatings with almost no erosion and they don’t get hard or brittle. Silicone is also good in ponding water situations.
Weaknesses: Silicones hold dirt and rain acts as a cleaner; therefore the material loses reflectivity over time. It is also hard to adhere to silicone, so when a roof needs re-coating, you must either remove the coating completely or re-coat with a compatible silicone. Resistance to tearing is a mechanical weakness and silicone coatings should be used with fabric as a common practice.
Roof Coatings should not be confused with deck coatings. Deck coatings are traffic bearing – designed for waterproofing areas where pedestrian traffic is expected. Roof coatings will only waterproof the substrates but will not withstand any kind of on going use by people (such as walkways, patios, sundecks, restaurants, etc.).
The National Roofing Contractors Association’s (NRCA) director of technical services has stated “The roofing industry is aware of a number of issues that could have negative consequences for field application of coatings. Anyone considering this type of application should be aware of the concerns so they can weigh them against the benefits claimed in coating product materials.
Most flat roofs are not perfectly sloped, causing water to puddle in some areas, in particular around the drains and scuppers. Many roof coatings are not rated or warranted for “ponding water”, and thus might fail pre-maturely if exposed to standing water over long periods of time. Serious consideration should be given to the performance and limitations of the coating being selected. Some manufacturers will warranty their coatings including ponding water. Typically, manufacturers for acrylic roof coatings do not include warranties for ponding water, while some polyurethane roof coatings manufacturers will.