How Much Roof Coating Should I Use On My Roof?

Homeowners in the Tucson area who have flat roofs often ask, “How much roof coating should they use their roofs.”  The amount of roof coating you should apply depends on several factors, including the coating you are using, the condition of your roof, and the manufacturer’s recommendations. Here are some general guidelines to help you determine how much coating should be applied and how some roof companies like to skimp on materials.

Recommended Roof Coating Coverage

First, you should read the manufacturer’s instructions for their roof coatings. We at Desert Sky Roofing use Tucson Rubberized products, and primarily their 7000 product and they provide information on the application of their products on their Technical Data Sheet.  They recommend their product to be applied at 1-1.5 gallons per 100 square feet. All manufacturers of roof coatings have their recommended application information on their labels so that you will know exactly  how much roof coating to put on your roof. Any local roof coating specialist that does the job correctly should be able to tell you exactly how much roof coating to put on your roof according to the type of material they are using.

How To Calculate Roof Square Footage

Google Maps has a great measuring tool that many roofing contractors use to find the square footage of roofs. This tool is free and easy to use. Simply draw a line around your roof on maps and close the box in at the end. The tool will show the length of the lines and the approximate square footage of the roof. Now if you have pitched roof you will need to add 5-10% for the pitch. Also, if you have a Santa Fe style flat roof you may have roll up on the parapet walls that will need to be considered.  Using an imagery tool such as Google Maps is always best.  Going off your home’s living space is not very accurate and usually turns out much lower than the actual coverage area of your elastomeric roof.

How Much Roof Coating To Buy

With the manufacturer’s recommended application per coat and the square footage of the roof it is simple to find the amount of coating needed on the roof. First, divide the square footage by the recommended coverage per gallon.  For example, Tucson Rubberized Coatings recommends 1-1.5 gallons per 100 square feet so at a minimum every 100 square feet should receive 1 gallon of coating per coat.  Thus, if the square footage of the area for roof coating is 2000 square feet then divide that by 100 and you will find you need 20 gallons of roof coating for each coat, per the manufacturer’s recommendations. If you are doing two coats you will multiply that by two which comes to 40 gallons of material for two coats.   Most roof coating companies package their coatings into five gallon buckets. To find out how many buckets of material divide the number of gallons by five. So, 40 gallons of roof coating is equal to eight buckets of material. Desert Sky Roofing does this calculation for you and provides the exact amount of buckets recommended for each roof in each roof coating estimate.

How Thick To Paint Your Roof Coating

Elastomeric roof coatings are usually applied in multiple thin coats to achieve the recommended thickness. The thickness is typically measured in mils (1 mil = 1/1000th of an inch). The manufacturer’s instructions will specify the desired thickness, often ranging from 20 to 30 mils. You may need to use a mil gauge or follow the manufacturer’s recommendations for achieving the desired thickness. Most often the proper millage is accomplished by applying two coats of the material. The millage is determined after the liquids have evaporated and the solids are left on the roof. The easiest way to make sure the proper millage is achieved is to apply the recommended coats to the roof prescribed by the roof coating manufacturer.

More Roof Coating For Older Damaged Roofs

If your roof is aged and the coating is peeling or significantly thin you will probably need a little more roof coating than usual.  If it has been more than five years since you coated your roof then you can expect that it could take up to 10% more roof coating on your roof. Of course this differs per roof and this calculation should simply be a guide.  For sure the first coat will take more than the second coat, but overall the roof could take approximately 10% more roof coating overall.

How Roof Companies Cheat on Roof Coating

Unfortunately, many roof companies cheat clients on roof coating applications. They cheat on the amount of materials used and types of materials used. First, the most common ways they cheat is they will not apply the proper amount of material to your roof. They do this by spreading the roof coating too thin per coat.   It will still look great when they are finished but it will not last as long in the extreme Tucson weather. Remember, it is the mil thickness that is required to ensure these roofs to last longer. By reducing the materials put on the roof the roof coating is not as thick and when the roof expands and contracts in the heat and cool temperatures, the coating will tear resulting in problems on your roof. 

The second way roofing contractors cheat is to purchase cheap materials. Not all roof coatings are the same. Most often the more expensive coatings last longer but some roof companies want to save money by using the cheapest materials.  Cheaper materials have less solids and cheaper elastomers. This means it will be a thinner coating that does not stay pliable as long as other coatings.

Roof companies who spray the roof coating on the roof have a tendency to put less than the recommended amounts of coating on the roof. This is because they go faster and the spray tip applies the coating thinner than a roller would apply the material. When painting your roof you can either roll it on with paint rollers or spray it on using large airless spray pumps. We believe that rolling the elastomeric coating on the roof is always better because you can ensure the coating is properly applied.  Spraying the coating on the roof helps the roofer go faster but unfortunately it makes it very difficult to know how much coating is actually going on the roof. There is one exception: roofing companies can use spray pumps to deliver the roof coating to the roof and use a “backrolling” technique to roll the coating where it needs. By doing this the roofer can control the amount of material and use the pump to deliver the needed materials.  It is worth discussing the technique a roofer uses if they spray the coatings on your roof.  If they do not backroll then it is suspect if the right amount of material will be applied. Ask them how they guarantee the manufacturer’s recommended amount will be applied.

Tucson Roof Coating Specialists

Roof coating is not difficult to do but it is important that it is done correctly. This article should have helped with the question, “How Much Roof Coating Should I Use On My Roof?”  Whether you are using a roofing contractor near you or doing it yourself it is important to apply the elastomeric roof coatings in the proper way and with the proper thicknesses.  Desert Sky Roofing would love to give you a free roof inspection and help you know more about your specific roof. We love to teach about roofing and enjoy helping our clients make proper decisions about their roofs.  Give us a call today! We do roof coatings in Tucson and the surrounding area. If you have an Oro Valley roof coating job, a Marana roof coating job, a Casas Adobe roof coating project, a Catalina Foothills roof coating job, a Tanque Verde roof coating job, a Green Valley roof coating project, a Sahuarita roof coating project, a Tucson Estates roof coating job, a roof coating job in Vail, Drexel Heights, Picture Rocks, or any other location in and around Tucson we want to earn the right to be your roofing company!