Polyurethane foam and coating roof systems in the Southwest


Polyurethane foam and coating roof systems in the Southwest

In the southwest, and specifically in Arizona, where I do my business as a roof consultant, polyurethane foam and coating systems are very popular. There are lots of mixed opinions about them, good and bad. People love them, or they hate them. Or they don't understand them. 
The ease installation and its low cost. The potential for energy savings, especially in the heat of the Arizona sun. All make this a pretty popular system in Arizona and though out the southwest. 
Polyurethane and coating roof systems can be found on;
  • Industrial buildings
  • Commercial buildings
  • Shopping centers
  • Multi-family
  • Townhomes
  • Condominiums 
  • Single-family

What is polyurethane foam?
Scientifically speaking it's a synthetic polymer with urethane radicals, that is used to insulate building materials from corrosion and provide R-value. It can be soft or rigid, roofing we use the rigid foam. It is applied using spray equipment designed to mix the two parts that come together to form the foam. 
Most manufacturers require a minimum of 1'' of foam, applied in two "lifts" (layers) at 1/2'' each. The foam is an excellent waterproofer; however, it is also very vulnerable to ultra violate degradation. It cant be l exposed for any time at all. Especially in Arizona, the sun will destroy it!
Polyurethane foam can be applied to just about any substrate or existing materials. Notice I said "just about any" not everything can be foamed so be careful. It goes down fast, works excellent on otherwise hard to work areas. It is self-flashing and can be shaped and formed into whatever you need. For example, you can build crickets using foam to help create positive drainage. 
The Coatings

 The most common type of coating we find here in the southwest are acrylic coatings.  The inexpensive and there are a few manufacturing plants hear of it make them. The fact that they are less expensive and are readily available does make them a common choice in this market area.
The minimum dry mil thickness that you would want is 25 mils. This is their minimum mill thickness that the SPFA (Spray foam alliance) recommends. These are the people whom the industry looks to for foam and coating standards. Once you start getting below 25 mils and nearing 15 mils, your foam is more and more vulnerable to ultraviolet light and moisture damage. 
Acrylic coatings are known as sacrificial coatings, and over time they will wear out and wash off the roof. On average, you might expect to lose 1 mil a year in mils thickness.  For example, if you want ten years, then you’ll want 35 mills which are 10 miles above the minimum 25 Mils. 
Regular inspections can help you predict when a recoating is necessary and help prevent surprises. 
Silicone roof coating is not exactly new to the industry,   but It is a relatively new player in the market. Over the past few years, I’ve seen more silicone on roofs than in times past, and I expect that trend wind change and silicone will become a more significant player. 
Some roofers are still a bit gun shy about it and avoid it. In my opinion, contractors who avoid either don't know how to apply it properly or they don't want the extra expense in equipment to spray it. Silicone is more or less sand, and the product can put some wear and tear on spray equipment. 
Unlike Acrylics which are organic, silicone is a nonorganic material. It is also not a sacrificial material such as acrylics are. It does not lose much if any mil thickness over time. It also can be applied as thick as you choose. It looses very little mil thickness when it cures. Typically, 25 mils of silicone coating are enough to provide adequate protection.
Silicone is a very water-resistant material and will withstand standing or ponding water much better and for a much longer time than acrylics. Which often start to show damage from ponding water within a day or two.
There are undoubtedly other coatings on the market; these two, however, are the most commonly used coating materials in the southwest. Protecting polyurethane coatings and for other roof restoration applications. 

Common problems
The number one reason for any roof system failure is installer error; the second is poor system design. Polyurethane and coating roof systems are easy to spot problems on, most of the time. Issues will appear as blistering, either the polyurethane is delaminated and blistering. Or the coating was misapplied, and you will see blisters in the coat itself. As mentioned previously in this article, two inspections per year will assure you catch any problems well in advance and make repairs before the roof fails. 
Finally, if the roof is leaking, you are too late. 

Polyurethane foam and coating systems are great when installed correctly. The bad rep that it gets sometimes has much more to do with the installation then the system. It offers R-value, and with a proper coating, it is also a radiant barrier, offering potential energy savings. It can be applied quickly; it is cost-effective and can be applied just about anything.
If you are considering polyurethane foam for your roof. Hire a contractor who specialized in polyurethane foam systems, and it wouldn't hurt to hire a roof consultant to help you throughout the project.  
Henry Staggs
Roof Consultant and Roofing Industry Advocate
(480) 265-1613