spray foam installed on a sloped roof

Can You Install Spray Foam on a Sloped Roof?

Greg PalyaSpray Polyurethane Foam Roofing

So, you have a sloped roof and you’re interested in spray foam roofing?

Congrats, you’ve come to the right spot!

Since West Roofing Systems has been installing spray foam over sloped roofs since 1979, we feel confident in answering all the top questions that building owners with a sloped roof are concerned with.

Let’s roll…

Can a sloped roof be installed with spray polyurethane foam?

Yes, you can install spray foam over a sloped roof.

Spray foam can be installed on any angle of a sloped roof, anywhere from a 1:12 to a 12:12, and right up to vertical.

If you’d like to know the slope of your roof, here’s a quick chart:

different slopes for a roof

If you’d like to determine roof slope yourself, use the same formula you used in your grade school years: rise over run.

For example, a 6:12 roof “rises” 6 inches for every 12 inches of “run,”or you can measure from the roof edge to the center to determine slope. Say your roof rises 72 inches from the edge to the center, and this goes over a 144-inch area.

rise over run on a roof to determine slope

Rise = 72 in.

Run = 144 in.

Slope = 72/144 = .5 = 6:12 slope.

Here’s a roof pitch calculator where you can enter your own dimensions if you’d like to take that route.

Does spray foam for a sloped roof cost more than a flat roof?

Yes. Installing spray foam on sloped roofs costs approximately 20-30% more than a flat roof. Here are three reasons why:

1. Need for additional fall protection (lifts, restraints, etc.)

On a flat roof, a lift is not needed to access areas where a contractor needs to spray foam because they can safely walk to where they need to be.

Fall protection is always required, but additional measures are required when the slope exceeds a 4:12 slope.

On some sloped roofs, the fall protection is a lift.

A good example would be a dome roof, where a lift would be a more cost-effective solution to get the job done efficiently than any other method of fall protection.

Using a lift vs not using a lift increases the cost of a roofing project, but safety is #1 priority on every roofing job.

2. They take longer to install

Using a lift or fall restraints systems in general slows down a sprayer’s installation rate by approximately 30-40%.

Every time you move, you need to stop spraying and hit a button, or you need to relay to a team member that you need re-positioned.

Having restricted movement as opposed to walking freely on a roof will increase the cost of a roofing project because it takes a longer amount of time.

3. Overspray exposure increases the chances for delays

One of the disadvantages to the spray foam roofing system is the constant element of overspray. Overspray happens when wind picks up the foam, causing it to land on a window, car, etc.

When you’re spraying foam out of a lift, it’s just you and a lift operator. On a flat roof where it’s windy, a sprayer will have a team member besides them to hold a wind screen to prevent overspray.

When you’re in a lift, there are no team members near where you’re spraying, thus, there’s no overspray protection.

The sprayer needs to be very aware of weather conditions and perhaps slow their rate of installation because there’s no overspray protection present.

Are there any differences in preparation for a sloped spray foam roof?


When you’re spraying over a sloped roof, the substrate is most likely going to be shingles or metal, so there are different preparations than those normally found on a flat roof, such as single-ply or BUR.

On a shingle roof, shingles that are curled up will need to be scraped off and replaced. If you remove the shingles and don’t replace them, they will cause an aesthetics issue as you’d notice the areas where there are no shingles.

On a metal roof, it could be rusted severely to a point where spot priming is needed prior to installing foam.

What safety concerns are present when spraying foam on a sloped roof?

Here are statistics from West Roofing System’s Director of Safety, Robert “Boz” Bosley:

roofers tied off on a sloped roof installing spray foam

  • There are no requirements where you NEED to use a man lift at a certain slope
  • Anything less than a 4:12 slope, you need to use at least a warning line system
  • Anything equal to, or more than a 4:12 slope, you need to use a regulatory fall protection system, such as a:
  1. Warning line system
  2. Guardrail system
  3. Personal fall arrest system
  4. Safety net system

What are some examples of a sloped roof with spray foam?

West Roofing Systems has sprayed foam over hundreds of commercial buildings with a sloped roof. One that comes to mind is Iowa Salt Domes and Utilities.

Here’s a before and after photo:

sloped roof dome without spray foam on it

Iowa Salt Domes & Utilities - spray foam roofing

Here is another at Al-Rec LLC in Millwood, WV. This metal sloped roof had severe wind damage that was fixed with a spray foam roof.

Here are before and after photos:

All-rec sloped roof with wind damage

sloped roof with spray foam installed

Ready to learn more about SPF for your roof?

As you’ve seen today, it’s 100% possible to spray foam on a sloped roof.

While it may be a little bit more expensive due to additional safety measures and the limitations of spraying foam while restrained or inside of a lift, any sloped roof can have spray foam installed.

At West Roofing Systems, we’ve done work on all types of sloped and flat roofs since 1979.

Here are some other questions building owners have requested answers to:

And if you’re interested in learning about all these questions and more, we have a free (no information required) guide that covers everything spray foam roofing related:

the ultimate guide to spray foam roofing

About the Author

Greg Palya

Greg Palya is the Digital Content Manager of West Roofing Systems, Inc. He has a B.S. in Marketing from the University of Akron and an MBA in Marketing from Walsh University. When he's not trying to teach others about spray foam roofing and silicone roof coatings, you can find him on the basketball court or golf course.