Can Foam Roofing be Installed Over an Existing Roof? Pros and Cons 

Spray foam roofing is a viable and effective option for Phoenix properties with flat roofing. Compared to other roofing materials, foam offers exceptional protection against deterioration and damage caused by the harsh Arizona climate. Home and business owners are also choosing polyurethane-based spray foam for its affordability, longevity, minimal maintenance needs, and perhaps most of all, its exceptional insulating capabilities that can help slash energy costs. 

At Pinnacle Roofing, we have a reputation for high-quality spray foam roofing backed by exceptional customer service. We use only the best products and methods to deliver reliable and long-lasting roof systems throughout the Phoenix Metro area.

Many clients considering spray foam roofing ask whether we can install it over their existing roof. The short answer is yes (in most cases), but there are some pros and cons to consider when choosing to go that route.

The Basics of Installing Foam Roofing in Phoenix

Spray foam proofing is not a standalone roofing product but rather part of a multi-layered roofing system that includes a wood roof deck topped by the foam layer, two different protective topcoats, and a decorative granule surface. Trained roofing professionals use specialized, high-pressure sprayers that combine and spray isocyanate and polyol onto the roof decking. The substance immediately expands and hardens, forming waterproof, durable, and high-R-value roof insulation. 

Since it requires a solid surface as a base layer, an existing flat roof may fit the bill. However, before planning to install a spray foam roof, consider the pros and cons of this approach as opposed to investing in a brand-new roof first.

The Pros and Cons of Installing Spray Foam Roofing Over the Current Roof 

In general, installing a spray foam roof over an existing roof is a convenient way to improve insulation on a flat roof without breaking the bank. However, spraying the current roof isn’t always the best option. Only an experienced roofer can determine whether your roof is a good candidate after a complete inspection and evaluation. 


The advantages of installing spray foam roofing include:

  • Affordability: Adding spray foam roofing to an existing roof costs less per square foot than an entire roof replacement. 
  • Less disruptive: Replacing the roof on any building is disruptive. Installing foam roofing is fast and eliminates the noise and debris of a construction project. 
  • Improved flexibility: Although spray foam roofing is most common on flat roofs, roofers can insulate pitched, domed, or irregularly shaped roofs in a wide range of materials with the product. 
  • Less environmental impact: Covering an existing roof with spray foam rather than removing it and building a new one eliminates construction debris that would otherwise fill landfills. Increasing energy efficiency with better insulation also reduces energy consumption and emissions, making your building more environmentally friendly. 


Foam roofing also has some disadvantages.

For example, this roofing solution must meet strict standards. Roofers can only apply spray foam to a roof surface that is clean and dry. Even a small amount of water or debris will disrupt the foam’s chemical balance and prevent it from working as intended. The existing roof structure needs to be in good condition as well because if it isn’t, the foam roof will deteriorate more quickly.

Additionally, the roof system may be incompatible with foam. If the spray foam is to over a roofing system like thermoplastic polyolefin (TPO), a single-ply membrane-style roof, the membrane must fully adhere to the existing roof deck. Unfortunately, because of the installation methods used for these roofs, some are not good candidates for spray foam.

For example, TPO roof installation often only secures the membrane to the roof structure at the seams. This allows the rest of the membrane to move up and down and change the roof’s slope, which can prevent proper drainage. Therefore, any roof system that doesn’t adhere the outermost layer to the one underneath is not suitable and needs replacing before applying spray foam; otherwise, the application is likely to be uneven.

It also may not comply with building codes. Building owners often save time and money by having contractors install a new roof over the existing one. However, if your building already has two or more roofing systems, adding spray foam on top of them may violate local building codes.

In that case, we may need to remove one of the roofing systems or replace the entire roof before installing the foam. 

Turn to Pinnacle Roofing to Learn More About Spray Foam Roofs 

Whether you want to install spray foam roofing over a new or existing roof, you need a contractor with training and expertise for a precise, long-lasting application. You can trust our professional roofers from Pinnacle Roofing to install a clean, level, and high-quality spray foam roof that stands the test of time.  We have 25 years of experience serving the Phoenix area, and you can trust our licensed and insured roofing contractors for honest and fair service. 

If you want to invest in a quality roof that lasts for 25 years or longer with minimal maintenance, contact our Pinnacle Roofing team. We can show you how to increase your Phoenix property’s energy efficiency with a reliable, watertight, and attractive commercial roof. Our trustworthy team has years of industry experience and a reputation for excellence thanks to a commitment to 100% customer satisfaction.

Let us help you decide if installing foam roofing over the existing roof is the right option for your building. Call us at 623-471-7096 to request a free consultation and estimate today. 



Phoenix and its nearby cities benefit from our range of professional roofing services. Be it your personal or business needs, we strive to make a positive difference in the region!

  • Scottsdale
  • Paradise Valley
  • Cave Creek
  • New River
  • Glendale
  • Peoria
  • Buckeye
  • Surprise
  • Goodyear
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  • Mesa
  • Gilbert
  • Chandler
  • Queen Creek
  • Apache Junction
  • Fountain Hills


Rely on our experienced roofing professionals for top-quality service and reliable results.