EPDM Ballasted vs. Adhered vs. Mechanically Attached

EPDM roofing membranes are among the most popular in the low-slope commercial roofing industry. EPDM offers building owners excellent durability, warranty, and energy savings regardless of installation method. However, the best installation method for the job can offer building owners even more benefits.

Learn about the different advantages of EPDM system attachment methods so you can make an informed decision when partnering with an Elevate roofing professional. The most suitable EPDM installation method for your structure can help lower overall roofing costs.

Ballasted, Mechanically Attached, and Adhered EPDM Systems Comparison

EPDM (ethylene propylene diene terpolymer) roofing systems are one of the most widely used roofing solutions and make an excellent choice for a resilient, sustainable, and durable roof. EPDM systems are time-tested and have earned a strong reputation for reliability, performance, hail resistance, extreme weather endurance, and long-term durability. But you can get more out of an EPDM roof by choosing the most suitable installation method.

Let's compare the three ways a roofing professional can install an EPDM single-ply membrane.

Ballasted EPDM

Ballasted EPDM roofs are some of the oldest single-ply roofing technologies, and they account for approximately 35% of EPDM installations today, according to the EPDM Roofing Association. These systems date back to the 1960s and are still used for their effective performance.

The ballasted EPDM roof installation is relatively simple — the insulation and EPDM membrane are laid loosely over the substrate and held in place by river-washed stones or concrete pavers. It's necessary to flash the roof's perimeter and penetrations, but the ballast weight keeps the entire roof assembly securely in place.

Aside from simple and fast installation, ballasted systems can also be implemented during almost any weather. A roofing professional can use large EPDM sheets to cover the roof quickly. Since there is no labor-intensive process like fastening or applying adhesive, it's possible to save on labor and material costs, too. Elevate RubberGard™ EPDM systems come with up to 90 mils overall thickness and up to 50 feet wide, making them a perfect choice for quick-to-install ballasted EPDM roofs.

Ballasted EPDM roofs are also sustainable and energy-efficient. The roof won't have thermal bridging since no fasteners are used during the installation. NRCA Roofing Magazine states that 3-8% of insulation's R-value is lost through mechanical fasteners' thermal bridging.

In addition, ballasted EPDM roofs act similarly to cool, reflective roofs to help improve a building's energy efficiency and help reduce a property owner's energy bills. An Oak Ridge National Laboratory study showed that ballasted roof systems performed equivalent to or better than traditional cool roof membranes, according to Architect Magazine.

However, the roof's slope, height, and structural deck can be the limiting factor for ballasted roofs. The deck must be designed to support the ballast weight, which is a minimum of 10 pounds per square foot (49 kg/m2). In addition, ballasted EPDM systems are best installed on roofs with minimal openings and penetrations.

Mechanically Attached EPDM

Unlike the ballasted system, mechanically attached EPDM roofs are lightweight and can be used on almost any low-slope or sloped roof (max. 4:12 slope). Mechanically attached single-ply roofing systems account for more than 30% of all North American commercial buildings, according to an NRC study.

The insulation sheets are either adhered to or mechanically attached to the roof deck with insulation plates and fasteners. Then, the EPDM membrane is laid over the insulation, and adjoining EPDM sheets are mechanically attached with seam plates and fasteners. The roof perimeter is also mechanically attached or fully adhered while penetrations and openings are flashed. Typically, fasteners are applied at the membrane's edge and covered with the edge of the next sheet, which is adhered over the seam.

Mechanically attached EPDM roofs are cost-effective, durable, versatile, fast to install, and lightweight. As a result, they are a popular choice in re-roofing applications and can meet various wind-uplift requirements.

To mechanically attach an EPDM roof, the deck must provide a minimum fastener pullout resistance of 400 lb (1.8 kN). However, Holcim has designed a system of alternate fastener spacing to be used based on fastener pullout capacity.

This EPDM attachment method is relatively affordable but has some drawbacks. Due to the nature of EPDM fastening, the membrane is free to move in the wind, which can cause fluttering sounds. In addition, the mechanical fasteners can serve as a thermal bridge and may reduce insulation efficiency.

Adhered EPDM

Fully-adhered EPDM roofs offer the highest wind-uplift approvals and can be used on low slopes or roofs with unlimited slopes. In addition, Elevate EPDM adhered membranes can be installed on roofs up to 250' (76.2m) high and be eligible for up to 30-year warranties.

Unlike mechanically attached membranes, the fully adhered EPDM membranes don't flutter and have no indoor air intrusion into the roof assembly. As a result, fully-adhered EPDM membranes are more energy-efficient, according to EPDM Roofing Association.

The insulation must first be mechanically fastened or adhered to the deck to install an EPDM roof. Next, the EPDM membrane is bonded over the insulation using adhesives and seam tapes. Almost every roof is a good candidate for an adhered EPDM system thanks to its flexibility and light weight.

Traditional adhered EPDM roofs take longer to install compared to mechanically fastened systems. However, a self-adhered EPDM membrane, such as RubberGard™️ EPDM SA, can make the installation process a breeze thanks to a pre-applied adhesive across the entire surface of the membrane. Unlike traditional adhered EPDM roofs, where you'd manually apply adhesives and seam tapes, a self-adhered membrane comes with adhesive already in place.

For context, a traditional adhered application on a 30,000 SF roof requires about 115 5-gallon pails of bonding adhesive and 33 rolls of seam tape. As a self-adhered membrane, RubberGard™️ EPDM SA requires no pails of adhesive and no rolls of seam tape. All that would be needed would be to strip in all end laps using 6" QuickSeam Batten Cover or 18" QuickSeam SA Flashing (cut to size) and seal with Lap Sealant.

Contractors have to deal with materials and labor no matter the EPDM roof system chosen. But, self-adhered membranes eliminate the need to haul some materials like adhesives, fasteners, and ballast to the roof.

Reach Out to an Elevate Professional Near You

All three discussed EPDM roofing systems work well for their intended purposes. But the building's roof design and condition, location, and building use can influence the roof selection. This article provides a "50,000-foot" overview, but there are many nuances to consider regarding EPDM roof installation. Reach out to an Elevate sales representative for help understanding the best EPDM installation method for the job at hand.