Is EPDM Better Than Felt? – A Detailed Comparison

There are basically three materials that most contractors suggest to customers when it’s time to install a flat roof. These are EPDM, Felt, and TPO.

In a previous blog, we delved into the properties of TPO and EPDM to see how they differ and which circumstances they are best suited for. In this article, we will analyze the composition, characteristics, installation, and performance of EPDM and Felt in order to answer the question: ‘Is EPDM better than Felt?’

First, what exactly is EPDM flat roofing?

EPDM, stands for Ethylene Propylene Diene Monomer, is a type of synthetic rubber made from ethylene and propylene. It is used in many different industries to make items such as gaskets, car window linings, tubing, and of course roofing.

As roofing, EPDM is available in black and white. White EPDM roofing is preferred in cases where higher reflectivity is desired. White roofing reflects more heat away, reducing air conditioning costs.

EPDM is produced in various thicknesses – 0.045, 0.06, and 0.09 inches. Most contractors use the industry standard of 0.06 inches, which is very close to the thickness of a quarter.

Different manufacturers of EPDM produce different variations of the material, to be used with various adhesives and application procedures. For example some EPDM sheets come attached with fleece material on the back side, which supposedly increases its strength and helps to distribute tension across the roofing. Another kind comes with a sticky back and is reinforced with fiberglass strips. However, despite the variations, they are all still EPDM and therefore exhibit largely the same behavior.

EPDM roofing membrane also comes in a variety of widths ranging from 7.5 to 50 feet. Sizes include:

• 1-meter wide and 10-meter long strips
• 3-meter wide by 15 meters long
• Some types of EPDM, such as the basic plain version, can be cut to the exact size of the roof, say, 20M X 20M.

Properties of EPDM 

• Resistant to high temperatures
• Adaptable to low temperatures
• UV resistant
• Waterproof
• Steam resistant
• Resistant to weathering – However, prolonged exposure to extreme weather such as hail, wind, snow or sub-zero freezing temperatures will negatively impact the lifespan of your EPDM roof.
• Flexible – 600% elongation and a tensile range of 500-2500 psi

What is Felt roofing?

Felt roofing, also known as modified bitumen, is an evolution of the age-old roofing method known as built-up roofing system, which involved applying multiple layers of asphalt between ply sheets (or felts) over the roof deck and insulation. It is called modified bitumen because unlike regular asphalt, this is bitumen that is polymerized rubber or plastic. 

Modified bitumen is a single-ply roofing system, meaning it can be applied in a single sheet only. However, some contractors add sub-layers of other material such as fiberglass sheeting in order to increase the strength and durability of the roof.

Modified bitumen roofing is also known as torch down roofing because its installation involves use of an open-flame propane torch to heat the bitumen membrane so that it can adhere to the roof deck.

Felt roofing is thicker than EPDM, which gives it an upper hand when it comes to prevention of punctures and tears. 

Properties of Felt

Longevity – Felt roofing can last up to 20 years.

Hardiness – Modified bitumen roofing can withstand both high and low temperatures due to polymer modification. Reinforcement with other materials such as fiberglass also improves its durability.

Waterproof – Modified bitumen membrane is thick and non-porous.

Energy efficient –  Has insulation properties.

Pros and Cons of EPDM roofing

Pros of EPDM as roofing	Cons of EPDM as roofing
Durable and low maintenance – EPDM roofing membranes are made of a unique synthetic elastomer rubber that has various desirable properties such as resistance to UV rays and extreme temperatures.  The synthetic rubber also doesn’t support the growth of moss.	Tricky installation – The most common reason for failure of all roofing systems, not just EPDM roofing, is poor installation. With EPDM, proper installation is even more because it is thinner than other membranes like modified bitumen. Proper measures include installers using foot mats to prevent tears to the EPDM sheets during installation.
Relatively more eco-friendly – Compared to other roofing systems such as TPO, EPDM roofing may be more eco friendly because old EPDM roofing is diverted from the landfill route to be reused and recycled.	Requires typically flat roof deck – As opposed to modified bitumen which can be applied over slight bumps and raises, EPDM is best placed on flat surfaces.
Custom sizes – With EPDM roofing membranes, you can contact your manufacturer to get sheets that fit your roofs exact dimensions. This helps to reduce seams which is always a good thing in roofing because it means there are less potential points of failure or leaking.
Reduce air conditioning costs – The black EPDM absorbs heat, reducing heating costs. White EPDM on the other hand reflects heat away, preventing overheating in the building and reducing cooling costs.
Easy and cheap repair – Repairs typically involve cleaning the damaged area, then applying new adhesive or flashing tape.

Pros and Cons of Felt roofing

Pros of felt roofing (modified bitumen)	Cons of felt as roofing (modified bitumen)
Tear-resistance – Felt / modified bitumen is very dense and hardy, making it resistant to impact from debris and heavy foot traffic.	Fire hazard – The use of open flames in applying the felt membrane is potentially dangerous since houses / construction projects can catch fire. However, when used carefully by skilled professionals, it is safe.  The danger of open flames is why the Department of Public Safety issued the Open Flame Policy in 2004.
Flexibility – The structure of felt allows it to expand when hot and contract when cool, without losing its structural integrity.	Potentially ugly repairs – A felt roof looks great when new. However, once it gets damaged and repaired a number of times, it can end up looking like rough patchwork.
Provides a highly water-proof and impenetrable roof surface – Bitumen, being a derivative of petroleum, is naturally waterproof. Along with other components, it makes the modified bitumen membrane completely waterproof, therefore you don’t need to worry about leaks, for a very long time.

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Image source: Roofing Today

So which is better, EPDM or Felt?

Both EPDM and felt roofing are good, however, we believe EPDM beats out felt. This is because EPDM, while more expensive, offers greater life expectancy than felt roofing. 20 years is the average guarantee a contractor will give when installing EPDM membrane on a residential client’s property. On the other hand, mineral felt generally has a general life of 5-10 years. In many cases, it can even fall below 5 years. However, this is more often due to lack of skill on the installers part, rather than the product being low quality. For felt roofing, the average guarantee a contractor will offer is 5 years.

Another reason we lean towards EPDM is because it is safer to install than felt. Many commercial sites have banned the use of a gas torch on site due to the potential danger to both the workers and t property. 

Additionally, EPDM comes in larger rolls, meaning less seams in the finished roof. Finally, EPDM offers greater durability than felt roofing.