incorrectly spraying foam on a commercial roof

6 Installation Mistakes Spray Foam Roofing Contractors Make

Greg PalyaSpray Polyurethane Foam Roofing

Have you ever gotten your car back from the dealership and you just pray everything works ok? Say you had transmission issues, paid a bunch of money for a rebuilt transmission, and for the first few months, that tranny is shifting smooth like butter.

But now it’s month four, and what used to be a smooth transition between gears had drastically turned into an ear-piercing metal collision that just screams “hope you have money saved for a new ride.”

You could’ve bought a bad transmission and were doomed for failure no matter what, or your mechanic could’ve done something wrong.

But how would you know?

The same scenario can be told about a spray foam roof.

Do you know how a spray foam roof is supposed to be installed correctly?

Since West Roofing Systems has installed over 60 million sq. ft. of spray foam over a 40-year period, we feel confident we can help you identify when your spray foam roof was installed correctly and when it wasn’t.

Buckle up, let’s get started:

6 Installation Mistakes Spray Foam Roofing Contractors Make

All spray foam roofing contractors aren’t created equally. Some have the clients best interest in mind, and some don’t. Here are some the common mistakes they make:


1. Spraying foam in too cold of weather

For spray foam to be installed correctly so that it performs the way it’s designed to; spray foam needs to be sprayed when the surface is at a minimum of 50 degrees Fahrenheit and rising.

This doesn’t include ambient air temperature.

The only temperature that matters is what the spray foam is going to adhere to.

Our advice to building owners: If a roofing contractor is on your roof spraying foam when it doesn’t meet these conditions, the foam will not mix correctly, which will make your foam roof system underperform.

2. The 3 energies of spray foam application is off

For spray foam to be installed correctly, it needs three types of energy:

  1. Electrical – the equipment used in mixing/heating foam
  2. Environmental – the air temperature, deck temperature, sun, etc.
  3. Exothermic – the heat created from the chemical reaction when the A and B components meet

You need all three energies synced for foam to be laid down (and cure) correctly. Here’s an example of how changing energies can affect a spray foam job:

Say it’s October and you have a regular speed of foam that’s meant to be used on 65-90-degree deck temperature. Today, it’s 65 degrees, so you’re at the bottom end of that speed of foam.

There are two energies that are lacking:

  • Environment – the deck temperature is below what’s recommended (not controllable)
  • Exothermic – the chemical reaction will be too slow because the foam was meant to operate on a 65-90-degree surface (controllable)

Solution: A roofing contractor will need to increase the amount of heat used in the equipment to mix the A and B side. Also, you may need to order a faster reacting foam to increase the exothermic energy.

The point is that though the environment is never controllable, the other two factors can be by adjusting equipment temperatures or using a faster or slower speed of foam.

Our advice to building owners: before you agree to a spray foam roofing project, ask the salesman if they know about the chemistry of spray foam.

3. Bad mixing of spray foam materials

For spray foam to be sprayed correctly, there needs to be a 50/50 mix of two chemicals.

The two chemicals are an “A” side, an isocyanate, and a “B” side, a polyol/resin.

These chemicals are pumped from separate containers through heated, high-pressure hoses to an internal mixing spray gun.

If a roofing contractor doesn’t have a proper mix, problems can happen, such as:

  • An incomplete reaction can cause blisters to form
  • Having a lower yield on product
  • A lower percentage of closed cell composition

Our advice to building owners: You aren’t going to know if a roofing contractor has the proper mix of chemicals before spraying, but you could ask about years of experience, as well as references to assure the roofing contractor has had other successful projects.

4. Installing spray foam over an unclean surface

A roofing contractor needs to verify that all surfaces are clean, dry, and free of dust, dirt, debris, oil, solvents, and any material that may affect the adhesion of the foam.

On a built-up, this includes removing all loose and poorly embedded aggregate surfacing material by use of a power broom, wet vacuum, or other suitable means.

On a metal roof, this includes removing loose scale, rust, and chalking paint using a wire brush or scraper.

On a rubber roof, this includes removing any debris with a power broom.

On all roofing types, the roof will be power washed at a minimum of 3500 PSI.

A popular phrase at West Roofing Systems is, “If you’re eating lunch on this roof and you dropped your sandwich, would you pick it back up and eat it? If not, the roof isn’t clean enough”.

Our advice to building owners: if you notice that a spray foam roofing contractor does not clean anything off your roof before spraying foam, a problem with the system is going to happen.

You can also look in your quote to be sure that some sort of cleaning is involved before installation.

5. Installing spray foam over wet insulation

Here’s a typical scenario:

A building owner has a roof that’s leaking, but only wants the roof to last 10 years. They just want the cheapest option that will get them 10 years until they retire or move away from the building.

They get a few quotes.

One is to install spray foam over the existing roof without removing the saturated areas, the other is to spray foam after removing the saturated areas.

The extra work involved to remove the wet insulation and replace those areas with similar (and dry) materials will cause that quote to be higher.

The building owner compares the two quotes and chooses the cheaper option.

Do you see a problem with this scenario?

The problem is that there are multiple dangers with installing spray foam over wet insulation.

In short, blisters will form which not only cause waterflow to become unpredictable, but those blisters can pop and create leaks.

What happens when those 10 years are up?

No one is going to purchase a building that has a leaky roof that needs repairs. A building inspector is aware of similar shortcuts and will force the building owner to make roof repairs or offer a credit.

Why not get the roof repaired right the first time…and create an awesome selling point by explaining how the roof is renewable to the new building owner?

Our advice to building owners: don’t trust any roofing contractor who explains that it’s okay to install a spray foam roof over wet insulation. This will only create headaches in the long term.

6. Install the wrong coating system

Did you know that the greatest weakness of a spray foam roof is its inability to resist ultraviolet rays of the sun?

It’s true. Spray foam will degrade approximately 1/16th of an inch per year when not protected with a coating.

To combat this issue, a protective coating is installed on top of it.

The three most popular types of coatings are acrylic, silicone and urethane. Each has positives and negatives:

Acrylic – water-based coating that’s only applied to roofs with a slope. If an acrylic roof has standing water (meaning the water just sits there and does not run off the roof), the standing water will cause the reversion of the coating back to a fluid and eventually wash right off your roof.

Silicone – a silicone resin-based coating that’s 96% solids/4% carrier. Which means 96% of what goes down on your roof will stay on your roof. Silicones perform great on flat roofs because they can withstand ponding water. Silicones are a middle-of-the-road coating in terms of performance and price.

Silicones are twice as resistant to weathering than acrylics, but also more expensive.

Urethane – urethanes have the most impact resistance of any elastomeric roof coating available. However, urethanes are very expensive compared to the other two and do not hold up to standing water very well.

You can see possible issues if a roofing contractor installs acrylic onto a foam roof with no slope (does not hold up to standing water) or if a roofing contractor quotes you with installing a urethane coating (could be an unnecessary added cost to your roofing project).

Our advice to building owners: ask the roofing contractor why they chose the coating they chose. A roofing expert should be able to explain very clearly why they are recommending which coating system for your commercial roof.

Final statement about incorrect spray foam installation

A common statement is “A craftsman needs years of experience in order to install a smooth, uniform, high quality spray foam roof.”

This is not true!

A craftsman that understands the 3 E’s of spray polyurethane foam, and keeps their equipment maintained and clean will consistently install high quality spray foam roofs.

Want to learn more about spray foam roofs? Other popular questions that building owners seek answers to are:

At West Roofing Systems, we want building owners to be aware of everything spray foam related so they can make the best roofing decision possible.

If you have any other questions about spray foam roofs, please visit our contact us page and submit your question there.


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.