SPF vs Built Up Roofing

SPF vs. Built-Up Roofing: Which is Best for a Flat Roof?

 

When you think of a commercial roof, you may think of black tar being mopped on a flat roof. But nowadays you have more options to meet your pricing and performance needs.

What is the difference between “traditional” built-up roofing and Spray Polyurethane Foam Roofing?

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 built-up and SPF roofing systems to give you all the information you need in choosing which roof is the best fit for your facility.

 

The Basics

Built-Up Roofing

Tar and Gravel Roofing

Tar and Gravel Roofing

Built-Up Roofing Systems have been in use in the U.S. for over 100 years. These roof systems are commonly referred to as “tar and gravel” roofs. Built-up systems are installed by alternating layers of asphalt or tar and supporting fabrics directly onto the roof. You can choose the number of layers (or plies) that are installed. The final layer of a built-up roofing system consists of stone or gravel.

 

Spray Polyurethane Foam (SPF) Roofing

Spray Polyurethane Foam, more commonly referred to as SPF, is a liquid that is sprayed on the existing roof 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

 

 

Cost

Built-Up Roofing

For an average commercial roof, it will usually cost between per $5.50 – $8.50 square foot in materials and labor to install a typical built-up roofing system. This price range can change depending on the materials you choose.

 

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

 

 

Installation

Built-Up Roofing

West Roofing Systems installs SPF Roof on Parma Ice Rink Building

West Roofing Systems installs SPF Roof on Parma Ice Rink Building

The first layer can adhere directly to the roof substrate. If needed, a base sheet can be fastened to the roof to create a flat and safe workspace. A built-up roofing system is installed by alternating layers of bitumen and reinforced fabric. Property managers can choose three, four or five ply roofs to meet their needs and budgets.

The last layer is rock or stone, this layer protects the underlying layers from UV rays, extreme heat or cold, and wind damage. A layer of gravel can be added to be more aesthetically appealing.

 

SPF Roofing

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

 

Advantages

Built-Up Roofing

If properly installed and maintained, a commercial built-up roof can last 40 years. There are a few other benefits of built-up roofing systems:

  • Seamless and Waterproof – The continuous solid surface does not require joints or seams, removing the most vulnerable area for leaking.
  • Reflects UV Rays – provides ultra-violet protection.
  • Low- maintenance – Minimal upkeep needed after installation.

 

Read More: Asphalt Roofing Manufacturers Association

 

SPF Roofing

When 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. The materials that are used for SPF roofing systems are also environmentally friendly: Zero Ozone Depleting Potential (ODP), Low in the Emission of Volatile Organic Compounds (VOCS), Free from Chlorofluorocarbons (CFCS), Ultra-Low Global Warming Potential (GWP).

 

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

 

 

Disadvantages

Built-Up Roofing

Built-up roofing systems have been around for decades; their longevity can only be obtained if the roof is maintained properly. Here are other disadvantages of built-up roofing systems:

  • Time – Slower installation timeframe
  • Safety – Hazardous fumes and vapors when installing it
  • Weight – Adds extra weight to the building structure
  • Costs – Installation costs
  • UV Rays – Without the gravel top layer, UV rays can break down the membrane quickly

 

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.
  • Maintenance – SPF roofing systems need to be inspected twice a year at least.

 

West Roofing Systems, Inc. installs sustainable and efficient roofing systems for commercial, industrial, manufacturing and municipal buildings. In over 37 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 facility’s roof, fill out our quote form for your free no-obligation commercial roof quote from our team of experts.
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Author: Aubrey Barto

Aubrey Barto is the Marketing Manager of West Roofing Systems, Inc. She has two BAs in News and Media Production with Certifications from Hubspot, HootSuite, University of San Francisco and Wharton School of Business. Aubrey works closely with West Roofing’s sales and service teams, she is up on our roofs taking photos and videos for our website regularly.

2 Comments
  • Many thanks for this comparable study! It is obvious that SPF holds an edge over built-up on most of the parameters.

  • Toller Spear

    at Reply

    Great post! We’ve been looking at SPF for some time, and this helps in the decision to go that route. It makes sense when you weigh the pros and cons!

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