While liquid-applied roofing systems as a whole continue to rise in our industry, silicone coatings continue to rise as well. I hate to be a naysayer and publish an article that could be perceived as a negative view on a particular product, but I don’t view it that way. Industrial and institutional facilities are at the core of our business and providing appropriate, sensible information in order to make good roofing decisions is a positive thing. Roofing products on industrial facilities are exposed to a different set of conditions, beyond Nature, and industrial roofs are used differently than a standard commercial facility. So why are silicone products a bad idea for industrial roofs?
Let’s start out with the most important, physical and life safety. Installing a silicone roof coating system on an industrial roof is unsafe. Silicone is extremely slippery, even when it is dry, and increases the risk of someone falling and hitting their head or becoming injured. I’ve witnessed it firsthand on a silicone-coated roof and a TPO roof. This increases the liability of the building owner and sets up HVAC technicians, maintenance workers, and other tradespeople for potential injury. While silicone can be “granulated” to be more slip-resistant by broadcasting granules into the surface, this is not a common practice because the granules end up causing the silicone coating to split and tear. It also adds cost and results in greater dirt pick-up, meaning it is back to a slippery surface after a few years.
Slip-resistant walkways and walk pads are standard on industrial roofs, but everyone is fully aware foot traffic outside of these areas is necessary and common. They cannot be relied on or expected to keep people safe. Coating an industrial roof, or any roof with foot traffic on even a semi-annual basis, with silicone is not worth the risk. There are far too many safer options.
REPAIRS & MAINTENANCE
Industrial roofs are unique because they require substantially more maintenance and repair work. Imagine a factory where a new vent stack is added through an existing roof. This roof had been coated with silicone and now the new penetration needs to be properly flashed in. You have one option: silicone. And you have to make sure it is the right kind of silicone, use reinforcement fabric, and ensure it will properly bond to the existing, aged silicone. The next week, a technician accidentally damages the roof while working on a piece of equipment. The damage is extensive and requires a small section to be completely removed and replaced with new insulation. How do you flash the existing membrane under the silicone into itself? Without removing some silicone, you can’t, because nothing can be overlapping over the silicone (even if you screw it down). The roofing contractor must do the full repair with only silicone. It’s just not good roofing practice.
Nothing sticks to silicone but more silicone. When you re-caulk your bathroom tub, do you apply silicone caulk over the existing silicone caulk? No, it has to be removed and re-caulked. Once an entire roof is coated with silicone, or even if a silicone patch is made, nothing will adhere to it. This ties the building owner to silicone until the roof is completely replaced. Emergency leak repair? Nothing can be used except silicone. An industrial roof needs to be able to be efficiently and quickly serviced by a variety of roofing products, from emergency patches to flashing in new penetrations or curbs.
TEAR STRENGTH & DURABILITY
Silicone has become popular as a similarly priced alternative to acrylic because it has better resistance to ponding water and is quicker to apply. But industrial roofs take a beating. This includes foot traffic, equipment servicing and changes, Mother Nature herself, and sometimes harsh chemicals. Silicone’s tensile strength and elongation is a little higher than an acrylic, but its tear strength and dimensional stability raises a red flag. If cured silicone film comes under stress (damage, foot traffic, structural movement) and tears, the tear easily and quickly continues to progress through the film. I compare it to a piece of cheese. When a tear begins in a silicone film, it continues to split with little force, like tearing a piece of cheese in half. I am hearing more and more from contractors about these continuous splits happening throughout the country. How is this repaired? You guessed it, more silicone.
While there may be a place for silicone roof coatings in our industry, it is my professional opinion it is not a feasible, smart option for industrial, or institutional, roofs. There is no justifiable reason to install a slippery, unsafe material on a flat surface over these types of roofs. And with the need for roof systems that are easy to repair and maintain, without being easily prone to damage and tears, there are much better options to consider.