How Many Gallons of Roof Coating Do I need?

Whether you are coating your roof yourself or you are hiring a roof coating contractor it is best to know how many gallons of roof coating your roof needs to be properly coated. It is not difficult to find out how much coating is needed so here are a few things that will you determine how much to put on your roof.

How To Determine The Square Footage Of Your Roof

The amount of roof coating needed on your elastomeric coated roof primarily depends on the amount of square footage of coverage. The coverage area is not the same as your home’s living square footage. In fact, it can be significantly more. In Arizona, the living space does not include the garage, porches, overhangs, and parapet roll ups. Each of these elements adds to the overall roof coating that is needed. The best way to determine the elastomeric coverage area is to purchase a measuring roller and roll out the exact amount of coverage. Remember, the square footage of a rectangle or square is found by multiplying the base and the widths. A = B x W. To find the square footage of a triangle area multiply the base and the height and divide by two. A = (B x H)/2. These simple equations will help you. We recommend walking your roof and adding up the different sections until the entire square footage of the roof is determined. Don’t for get to roll the parapet sides that have roof paper that will also need to be coated.

If you are not keen on getting on your roof, you may go to and find your home. Google maps has a measuring option where a perimeter line can be placed around the entire coated area. By following the perimeter and connecting the lines, Google will estimate the square footage. Remember that this square footage does not include the rise of the roof (if it is a ranch style roof), nor does it consider the roll up on the sides. By using Google Maps one can get a relatively close idea of the square footage but it will likely be lower than the actual number.

How To Determine How Many 5 Gallon Buckets of Roof Coating Are Needed

Once the square footage of the elastomeric roof coating area is determined this number will need to be checked against the manufacturer’s recommended application numbers. Each manufacturer of roof coating has a square footage recommendation for their specific coating. Tucson Rubberized 7000 (the coating we prefer), recommends their coating be applied at 100-150 square feet per gallon. That means a 5-gallon bucket will spread anywhere from 500-750 square feet. At Desert Sky Roofing we recommend shooting for 600 square feet per bucket or 120 square feet per gallon. It is our opinion that 150 square feet per gallon is too thin for most roofs.

If your roof coating coverage area is 2400 square feet it will take 20 gallons per coat, or four 5-gallon buckets of Tucson Rubberized 7000. If you are planning on using a different coating, check the recommended application of that particular coating to determine the coverage minimums.

Other Factors To Consider When Determining Roof Coating Coverage

One of the other factors that will determine how many gallons of roof coating you need for your roof is: How long has it been since you coated your roof? The longer a roof sits without attention the more initial coating will be needed to recoat the roof. This is why manufactures of roof coatings provide a range for the square footage. If the roof has not been coated for 4-5 years expect to get a lower coverage of material because of the roughness of the roof and the cracks and areas the coating will fill in. On the other hand, if you are applying a second coat, the roof coating will glide on smoothly and go much farther. As a general rule, for the materials we use, we calculate the first coat at 100 square feet per gallon and the second coat between 120-150 per square feet per gallon. If doing two coats we use 120 square feet as a general coverage rule.

A second factor that typically uses more coating is the amount of patching that is needed on a roof. If the roof is in pretty bad shape with many cracks, dry peeling, or the felt paper is showing, expect the roof coating to be soaked up in these areas. As a general rule add 5-10% on the square footage of the coverage area if you expect to do a significant amount of patching.

Finally, it is important to know how many coats you are going to apply. If your roof coating is over four years old, we recommend always applying two coats of elastomeric using the 120 square feet per gallon calculation. If your roof coating is younger then it may be ok to coat the roof with just one coat but we would always recommend applying the coating around 100-110 square feet per gallon. This will ensure the coating is thick and the previous coating does not bleed through. Another general rule to follow is that if you can see the previous coating bleeding through the new coating, not enough material was applied. When the coating is completed it should be one solid color – not streaky with different shades of white.

Call Us For A Free Roof Inspection

We would be very happy to come out and provide a free inspection of your coated roof. We can also provide a free estimate of our services. If you are interested in rolling on the roof coating yourself we have a Do-it-yourself Plan” in which we will show up to go over the roof with you, pressure wash the roof, and provide you all the materials needed to coat your roof. We can also deliver the buckets to the roof after we pressure wash. Give us a call at 520-444-5218 and we can work out all the details!