EPDM "Rubber" Roofing: The Complete Guide

What Is EPDM “Rubber” Roofing?

EPDM (ethylene propylene diene terpolymer), also referred to as EPDM rubber, is a synthetic rubber membrane that is widely used on low-slope flat roofs. It’s categorized as a single-ply roofing membrane, meaning it’s installed on roofing substrates in a single layer.

EPDM is manufactured in rolls at widths ranging from 7.5 to 50 feet and at thicknesses of 30, 45, 60, and 100 mils (1 mil equals 0.001 inches). Most EPDM membranes are black in color but are also available in white, gray, tan, and various other tints.

Top manufacturers of EPDM include Carlisle SynTec, Firestone Building Products, Johns Manville, and GenFlex, among others.

Cost-Effective

EPDM roofing systems cost anywhere from $4 to $10 per square foot. This is considerably less than asphaltic (multi-layer) commercial roofing systems such as modified bitumen and built-up roofs, but comparable to other single-ply systems.

Long-Lasting

Perhaps the most important characteristic of an EPDM roof is its long lifespan. A properly installed and maintained EPDM roof system can last as long as 40 years or more, which is considerably longer than other single-ply roofing systems.

Easy to Install

EPDM is a lightweight material that is quick and easy to install. The use of wider rolls can further cut down on installation time and labor cost.

Easy to Maintain

Wider rolls of EPDM yield fewer seams on the roof surface. Having fewer seams can significantly reduce maintenance and repair costs over the lifespan of the system.

EPDM membranes are also relatively easy to patch.

Environmentally Friendly

The manufacturing process of EPDM has minimal impact on the environment and the membrane itself is 100% recyclable.

Relatively Fragile

EPDM is susceptible to sudden damage caused by hail impacts, wind-driven debris, foot traffic, and rooftop equipment. This problem only gets worse as the membrane ages.

Shrinkage

Shrinkage is one of the most common problems affecting EPDM roofs. It’s a process that occurs gradually over time causing the membrane to separate (more commonly referred to as bridging) around parapet walls, seams, and penetrations.

Poor installation and design can accelerate the “shrinkage” process.

Not Aesthetically Pleasing

As EPDM roof systems age, they can become quite unpleasant to look at. This is due to the long-term accumulation of dirt, dust, and other foreign contaminants. Regular cleaning can help alleviate this unsightly (albeit superficial) problem.

Seam Issues

The seams of an EPDM roof are quite strong, but the adhesives that bond them together tend to dry out and weaken over time. This can cause tiny openings to form in the seams and penetrations, thus allowing water to enter the roofing assembly.

Other factors such as shrinkage and poor installation can magnify this problem.

Routine maintenance (more on this below) is the best way to ensure that all seams remain intact and watertight.

Is EPDM Energy Efficient?

There is some debate regarding the energy efficiency, or lack thereof, of EPDM. Actually, the answer to this question depends primarily on location and membrane color.

EPDM is commonly black in color, which is not ideal in warmer climates because dark membranes absorb more of the sun’s heat. This leads to excessive heat loads on the roof surface which increases cooling costs and accelerates deterioration of the membrane.

In colder climates, black EPDM membranes are the preferred single-ply solution because they retain more of the sun’s heat, which helps reduce heating costs.

White single-ply membranes such as TPO and PVC (aka cool roofs) offer far greater thermal reflectivity and therefore are far better suited for warmer climates. Roofs with greater reflectivity are more apt to withstand UV exposure and provide increased energy efficiency.

Side Note: Although EPDM is manufactured in white, it’s not nearly as common as other “default white” single-ply membranes such as TPO and PVC. This is likely due to the lower material cost and ever-increasing market share of TPO and PVC.

Ultimately, determining the suitability of an EPDM roofing system as it relates to energy efficiency depends on the number of cooling and heating days in a given location.

How Is EPDM Roofing Installed?

There are three different installation methods for EPDM roofing systems:

Mechanically Fastened

Most EPDM roofing systems are installed this way. This method utilizes metal fasteners and plates to secure the membrane to the insulation board and roof decking. It’s also the quickest and easiest method of installation.

Fully Adhered

For this method of assembly, the membrane is glued directly to the insulation layer with a specialized bonding adhesive. This type of assembly is the most time consuming to install but typically lasts longer. It also has the greatest resistance to wind uplift and provides a slight increase in energy efficiency.

Ballasted

In a ballasted system, the EPDM membrane is loose laid over the roofing substrate and held in place with smooth stones or concrete pavers. This type of installation method is the most aesthetically pleasing and provides the highest degree of energy efficiency.

What Causes EPDM Roofs to Fail?

EPDM roofs can fail prematurely for a number of reasons, but most problems are caused by lack of maintenance. Other common and potentially serious issues are shrinkage and defective seams.

As previously mentioned, EPDM roofs shrink as they age. Shrinkage is a gradual process that causes the membrane to separate (or bridge) in certain areas, specifically around parapet walls, seams, and penetrations. This puts increased stress on the membrane making it far more susceptible to damage.

Installers compensate for shrinkage by adding more material than is needed to the roof surface. In doing so, the membrane will essentially shrink to a proper fit as it ages.

Problems with the seams typically occur as the adhesives that bond them dry out and weaken over time. Once the seams begin to fail, it’s just a matter of time before water finds its way into the roofing assembly and saturates the insulation layer.

Other common problems that can “wear out” EPDM roofs over time include:

EPDM is also rather susceptible to sudden damage caused by severe weather, wind-driven debris, equipment additions, and tradesperson damage.

Recommended reading: 10 All-Too-Common Flat Roof Problems

The Importance of EPDM Roof Maintenance

Scheduled maintenance is an easy and cost-effective way to prevent most problems on EPDM roofs. The purpose of roof maintenance is simple: inspect the roof often (in the spring and fall) to identify problems and make repairs promptly and accordingly.

Roof inspections are an integral part of any routine maintenance plan. Most inspection processes center around a detailed, multi-point checklist in which every possible component (interior and exterior) of the roofing assembly is checked.

The basic intent of a roof inspection is to conclude:

Inspections should also be conducted following bouts of severe weather and service work on rooftop equipment (e.g., HVAC units, communication equipment, signage, etc.).

It’s also recommended that regular cleaning be performed to remove any dirt, dust, debris, and other unwanted contaminants. Foot traffic should also be kept to a minimum.

Repair Options for EPDM Roofs

Once problems are identified, steps need to be taken to keep any damage to a minimum. There are a variety of factors to consider when it comes to choosing the best course of action.

Note: Repairing an EPDM roof is not a DIY project. It requires the use of specialized roofing materials and equipment, not to mention many hours of hands-on training. To ensure a successful repair project, we highly recommend contacting a certified EPDM roofing expert in your area.

Repairing Minor Damage

In cases of minor damage such as punctures, splits, and tears, temporary repairs can be made with an industrial-grade roofing sealant. This will prevent water from entering the roofing assembly until a more permanent fix can be realized.

For most surface damage, a roof patch is the more appropriate and long-lasting repair technique. This type of repair involves the application of small patches of EPDM material over damaged sections of the roof surface.

Video: Click here to watch the installation of EPDM “rubber” roof patch.

Surface preparation is critical for these types of repairs. Affected areas must first be cleaned thoroughly to remove any dirt, dust, and other residue. This will ensure proper adhesion of the repair material to the existing membrane.

In many cases, the use of a primer is also required to sufficiently prepare the roof surface for repair.

Beyond “Simple” Repairs

As an EPDM roof nears its end of life, repairs are going to become more frequent and costly. At this stage, a complete and long-term solution is needed to keep the roof system safe and effective.

Determining the best course of action for an EPDM roof depends mainly on the level of saturation in the insulation layer. Options include:

Restoring EPDM with Roof Coatings

Restoring aged EPDM membranes with an elastomeric coating system can be greatly beneficial, especially in warmer climates. Roof coatings provide a highly reflective, bright-white finish that can significantly minimize the negative effects of the sun and vastly improve roof performance.

How Do Roof Coatings Work?

Roof coatings are applied in liquid form directly to existing roof surfaces. They cure to create a flexible, seamless, UV resistant, and watertight membrane that increases weatherability, improves energy efficiency, and prolongs roof life.

Furthermore, a roof coating system doesn’t require the removal of any existing roofing material, so the time and money needed to install one is considerably less than that of a complete tear-off and replacement.

The benefits of a roof coating system include:

Additionally, most roof coating manufacturers offer a variety of long-term warranty plans.

What Type of Coating Works Best on EPDM?

Solvent-based roof coatings such as silicone and urethane (polyurethane) work best on EPDM roofs. These types of coating offer the greatest resistance to ponding water which is likely to occur on low-slope flat roofs.

At American WeatherStar, we offer two flat roof restoration systems that utilize silicone and urethane coating technologies:

To learn if a roof coating system is the right solution for your commercial building, click here to find an American WeatherStar Approved Contractor in your area.

Recommended reading: Which Roof Coating Performs Best?