Single-Ply Membrane vs Spray Polyurethane Foam: Which is Best for Commercial Flat Roofs?


When we meet with future clients, they are usually comparing several types of roofing systems. We are always asked: Which is better? Which is more affordable? Which is best for long lasting protection?

At West Roofing Systems, we want to make sure that our future clients have the best information available. For this reason, we created an article that explores the differences between single-ply membrane and SPF roofing systems to give you all the information you need in choosing which roof for your facility.


The Basics

Single-Ply Membrane Roofing

TPO Single-Ply Membrane Roofing

Single-Ply Membranes are sheets of rubber and other synthetics that can be chemically adhered to insulation or ballasted creating a layer of protection on your commercial facility.

There are two main types of single-ply membrane commercial roofing: Thermoplastic Polyolefin (TPO) and Ethylene Propylene Diene Terpolymer (EPDM). They differ in their chemical makeup, how they are installed and their energy efficiencies.

Read More: Single-Ply Membrane Roofing: Installation & Performance


Spray Polyurethane Foam (SPF) Roofing

Seamless SPF Roof

Spray Polyurethane Foam, more commonly referred to as SPF, is a material that is sprayed and expands into a foam, creating a solid layer across an existing roof.

While SPF roofing is not the most known type of roofing material, the technology has been around since the early 1960s for industrial, commercial, and residential facilities.

Read More: Spray Polyurethane Foam (SPF) Roofing: Installation & Performance




Single-Ply Membrane Roofing

For an average 20,000 sq. foot commercial roof, it will usually cost between $3.50 to $7.50 per square foot for EPDM and $3.50 to $6.50 per square foot for TPO, including materials and labor warranty.


Spray Polyurethane Foam (SPF) Roofing

For an average 20,000 sq. foot commercial roof, it will usually cost between $4.00 and $7.00 per square foot in materials and labor to install a typical SPF roofing system. This price range is for an SPF roof of average thickness and building structure.

Read More: Cost of a Spray Polyurethane Foam Roofing System




Single-Ply Membrane Roofing

TPO Installation

The beginning of the installation process is similar between TPO and EPDM single-ply membrane roofing systems.

After the existing substrate is prepared, either by cleaning or removing the existing roof, the insulation is installed. There are a few types of insulation options the facility manager/owner can choose from Polyisocyanurate (Polyiso), Expanded Polystyrene (EPS), Extruded Polystyrene (XPS)

After the existing substrate is prepared, either by cleaning or removing the existing roof, the insulation layers are installed and covered by a cover board. There are three ways to attach the membrane to the cover board: ballasted, with an adhesive or mechanically fastened.

The significant difference between TPO and EPDM comes when it is time to adhere the membrane seams together. TPO uses a hot-air gun to melt down the membrane at the seams and fuse them together. EPDM is joined together with a seam tape.


Spray Polyurethane Foam (SPF) Roofing

Spray Polyurethane Foam Application Team

Before the installation can start, the existing roof needs to be prepared. Rather than stripping the existing roof, the contractor will most likely prepare the substrate by getting rid of all dirt, dust, and contaminants.

The first layer put down by the contractor is the polyurethane foam. This foam is created by combining two liquids as it’s sprayed onto the existing roof substrate. As the liquid is sprayed onto the existing roof, it expands to form a solid foam surface.

When the SPF layer has been completed, it is then coated with a layer(s) of elastomeric silicone or acrylic coating with embedded granules.

Free Download: The Essential Guide to Spray Polyurethane Foam Roofing



Single-Ply Membrane Roofing

If properly installed and maintained, a commercial single-ply membrane roof can last 30 years. There are quite a few other benefits of single-ply membrane roofing systems:

  • Proven Track Record – EPDM roofing has been used for commercial flat roofing for over 60 years. This amount of time on the market has allowed various laboratory and field studies to be performed and tracked.
  • Customer Choice of Insulation – Since single-ply membrane roofing does not include the insulation factor, as a customer you have more options to choose from to insulate your facility’s roof.
  • Class A Fire-Rated – TPO membranes and EPDM can achieve Underwriters Laboratories (UL) Class A fire resistance listings by adding fire retardant chemicals during the manufacturing process.
  • Reflective or Retentive – TPO is generally white and highly reflective. On the other side of the spectrum, EPDM is often described as “Black Roofs,” due to the natural dark color of the membrane.


Read More: Pros and Cons of Single-Ply Membrane Roofing Systems


Spray Polyurethane Foam (SPF) Roofing

West Roofing Systems installs SPF Roofing

If properly installed and maintained, a commercial SPF roof can last 50 years. There are quite a few other benefits of SPF roofing systems:

  • Energy Efficient – SPF delivers thermal, air, and moisture barriers to provide the highest R-value per inch.
  • Durable – The foam material can expand and contract with the building, decreasing the likelihood of cracks and splitting.
  • Seamless and Waterproof – The continuous solid surface does not require joints or seams, removing the most vulnerable area for leaking.
  • Environmentally Friendly – In most cases, there is minimal stripping of the original roof – eliminating the need for costly roof tear-offs and waste.


Read More: Pros and Cons of Spray Polyurethane Foam (SPF) Roofing Systems



Single-Ply Membrane Roofing

EPDM Roofing System

While the advantages of a single-ply membrane roofing system outweigh the disadvantages, there are a few things you should keep in mind. Here are disadvantages of single-ply membrane roofing systems:

  • Durability – Single-ply membrane roofing does not have a hard top layer to protect the synthetic rubber from dropped tools, gravel or loose screws from being pushed into the rubber membrane.
  • Seams – Although these seams are sealed either mechanically or with melting adhesives, they are still areas that are more vulnerable to leaks than other roofing systems.
  • Roofing Accessories – Penetrations such as skylights or vents need special attention during installation.
  • UV Rays – UV rays that shine directly on the roof can degrade the adhesives quickly over time.


Spray Polyurethane Foam (SPF) Roofing

While the advantages of an SPF roofing system outweigh the disadvantages, there are a few things you should keep in mind. Here are disadvantages of SPF roofing systems:

  • Hire the Right Professional – The contractor needs to be precise with the application and have a solid understanding of the chemicals they are using.
  • Limited Installation Window – Installation of an SPF roofing system cannot be performed during cold, windy, or rainy weather.
  • Overspray Potential – Since the SPF is installed by a spray application, there is a risk of the wind carrying overspray onto surrounding cars and other surfaces.
  • Limited Colors – The silicone coating that is applied to the foam comes in two colors: white and gray.
  • Maintenance – SPF roofing systems need to be inspected twice a year at least.


As you can see, both Single-Ply Membrane and SPF Roofing Systems have their benefits and drawbacks. Choosing which one is best comes down to a customer-by-customer basis.

West Roofing Systems, Inc. installs sustainable and efficient roofing systems for commercial, industrial, manufacturing and municipal buildings. In over 38 years, we have installed over 56,000,000 square feet of commercial Spray polyurethane foam (SPF), single ply membrane and other popular roofing systems.

If you are looking for maintenance, repair or replacement for your facilities roof, fill out our quote form for your free no-obligation commercial roof quote from our team of experts.

Download your guide today!

Author: Rufus West

Rufus West is a commercial roofing expert! You may see him on the West Roofing website and also on the West Roofing social media pages, giving fun facts and tips about the company and roofing industry.

Just like West Roofing System’s roof solutions, he isn’t bothered by water—it simply rolls off of his back!

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