How long do roof coatings last?
If I had a $1 for every time this question was asked I wouldn’t be rich but boy would I have a great long vacation. Sadly that question is not one that you can just answer with a number. There are so many variables that can change that number that we could write 10 pages on that topic. Although there are many variables that we can’t change or predict, but there are a few things that we can gleam from that can give us a great start. First let’s talk chemistry because those are a variable that we can predict. We will break these down into the Big 3, Acrylics, Silicon & Urethane’s.
Acrylics have been around in volumes since the mid 1970’s and have came a loooong way since then. I know of one manufacturer who pioneered acrylic coatings “Conklin Roofing Systems” that are currently on their 6th generation of Acrylic coatings and they continue to advance the industry. Acrylics are sacrificial in design, which is a common thing that many competitive chemistry manufacturers try to use to negate the proven performance of Acrylics. By sacrificial what I am stating is that the coating by design slowly sluff’s of material (micro mil thickness’s) to continue to self clean and renew the coatings reflectivity. This does not mean that they are bad coatings because they lose thickness’s over time.
Quality Acrylic coatings will lose .25-.5 mils/year and even poorer quality acrylics typically only lose .75-1.25/year.
This is why Mil Thickness is important, because even if they are losing as long as they have the needed mil thickness they will perform for quite a while. The main issue with acrylics and the main reason for failures found is the lack of education for contractors to understand that long term ponding water is detrimental to an acrylics performance. Another concern that needs to be dealt with on acrylics is grease/animal fat contamination. Oils can cause the acrylics to re-emulsify just as water can do which will drastically shorten the life span of the coatings, but there are spot treating options that we will discuss below. That being said if water isn’t going to pond or if the roof isn’t constantly going to be wet and trying to dry then a High Quality Acrylic can perform with and even out perform in some instances any other chemistry and cost less over a life cycle analysis. To put it in lay-mans terms acrylics are a great balance of cost vs performance vs ease of use.
Acrylics are easily colored, and come in a variety of flexibility and tensile strength depending on the expected life span or performance needed. Acrylics also offer proven long term sustainability at an economic cost. There are several 30+ year old acrylic roofs that are still in service and will remain in service for many more years to come as long as they are cleaned, maintained, and re-coated every 12-15 years. With today’s technology that number may soon be extended to every 20 year needing re-coats. Basically if it has a slope then there is an acrylic that will give great performance for that surface in most instances.
At about 50% what Acrylics are The Second largest chemistry by use is Silicone.
The second largest chemistry by use and one that has seen some great growth is the Silicone’s. Silicone coatings have had their challenges over the years and still carry a bad taste in many contractors eyes but they are seeing growth. I will be honest I am not a huge proponent of silicone but am perfectly fine with it used in areas that I see as its strength. Low sloped/flat coastal areas with limited dry time really can benefit from silicon, as well as roofs that get limited to no foot traffic. Silicone by nature is hydrophobic meaning that if you were to look at the surface area of silicone under a microscope it has a very tight cell structure and leaves minimal amounts of surface area for adhesion. That exact same physical property is what makes it extremely dangerous on any slope because water will bead up and then causes basically a hydroplaning situation under a persons feet. If installed on a slope that is then magnified by gravity it can have very bad outcome if precautions are not taken such as guard rails and walkway mats.
Where silicone gets that “safety con” is also what gives it it’s industry “pro” from. Silicone being hydrophobic allows it to be used in areas that pond water for longer than desired and not be as concerned about the detrimental effects of standing water that an acrylic would have. Silicone basically in some eyes makes coating a roof less of a concern if there is some standing water areas. That being said you should proceed with caution when coating any roof with standing water. Standing water can be caused by several different things and all need paid attention to.
First standing water can be from a leaking areas that has saturated the underlying boardstock and caused it to compress.
Once a boardstock is saturated and starts to compress it then allows even more water to stand in that area which is adding more weight to that area and causes even more compression compounding the issue. This is a main reason why the NRCA states that standing water is anything that is left in place over 1/4” deep after 48 hours of dry time. When 1 gallon of water weighs roughly 8# you can only imagine what 3-4” of water over any size of area can add up to in a un-approved dead load. The building’s structure is designed for a given dead load in designing it, and if you start throwing large ponded water areas on it then happen to get a large wet snow or a clogged drain it can be disastrous if the structure is over its bearing capacity.
Secondly although not much off the first reason, but somewhat different is that a roof substrate can be dry but the structure have a built in sag or structural component issue. By coating this roof and not dealing with the underlying problem you are now actually making the issue even worse. Using a silicone restoration system because it can take standing water on a roof that has an issue that needs fixed is not smart practice for you or is it going to move the Fluid Applied industry further. It’s more of a bandaid to a bigger problem, and that is my number one concern with silicon’s.
Manufacturers promoting we don’t have a ponding water exclusion in my eyes says more of a “buy our product we don’t really care if it should be used or not” . I am more inclined to use a Silicone from a manufacturer that says yes this will perform way better in ponding water areas, but we abide by NRCA standards and want to see water off in 48-72 hours because that is good roofing practices. Now ok before one of you very opinionated guys gets off your rocker, remember I am a 20 year veteran in the fluid applied industry and I know in some cases it is literally close to impossible to get water off an area and you have to deal with it in the best way possible and Silicone/Urethanes are your option.
Also I must make light of the fact that although silicone does not re-emulsify like an acrylic does, don’t think that it is a magic bullet when ponding water is a concern. Silicones do still absorb water, and even in small amounts in the right situations silicone will disbond and release from the substrate allowing water to get under the coating and then cause issues to the existing roofing system. More common in the Midwest and North with freezing temps. Silicones can weather great, but durability is a concern . This is another reason why the silicone manufacturers have implemented a urethane/silicon system that incorporates our final chemistry Urethane with a Silicone topcoat for durability and standing water performance.
Our final chemistry is Urethanes.
This chemistry is the smallest by gallons used, yet in my mind and many others holds the most potential. Urethane’s have been held back mainly because of financial driven reasons. Urethane’s are costly to produce and do to that reason there has been limited amount of funding for research to grow their market share of the coatings sector. But breakthroughs have helped lower some of that cost and now many more companies are looking into the urethane line of chemistry’s. Urethane’s bring several pluses to the table. Urethane has been successfully incorporated into other coatings as hybrid which helps bring tensile strength way up for durability and still maintains good dirt resistance as well as impact resistance.
Like silicon’s hydrophobic properties, urethane’s perform very well under ponding water as well. One of the main benefits in my eyes is two fold. Urethanes can typically be recoated with an Acrylic or Silicone so sustainability is great, but Urethanes also hold up very well with standing water and grease/animal fat contaminants. This makes Urethane’s as an ideal Base layer for numerous hybrid systems that can give us a legitmate life expectancy into the 20-30yrs all Fluid Applied and its self flashing & seamless.
As you can see there is a whole multitude of opportunity for product selection and advancements in technology such as Quick Set Catalyst coatings, Kraton based polymers and more that we will discuss in the future. But until then stay safe and spray on. Lets Hop to It.