Single Ply Roofing: Everything You Need to Know

Single ply roofing is the most popular type of roofing on the market. But choosing the right roof for your building is not a matter of mere popularity. You're not just selecting a material - you're investing in the future of your property. Make the wrong choice, and you could be blindsided with continual repair costs, a shortened roof lifespan, and a potential hit to your bottom line. 

So how do you know if single ply is the right choice for your building?

Here at GIDEON, we understand that this isn't a decision to be taken lightly. With over two decades of experience and tens of millions of dollars of roofs installed, we've witnessed firsthand how the right - or wrong - roofing system can impact your bottom line, and we're here to help.

In this article, we're going to leverage our wealth of knowledge to demystify single-ply roofing. We'll explain what it is, its advantages and disadvantages, and how it compares with built-up roofing (BUR) and metal roofs. We'll then dive into the main types of single-ply roofing materials: EPDM, PVC, TPO.

Ultimately, we’ll arm you with the information you need to make a decision that's financially sound and makes your roof a true asset, not a liability. 

Table of Contents

• What Is Single Ply Roofing?
• Single-Ply vs Built Up Roofs & Metal Roofs
• Single Ply Advantages Over Built-Up Roofing (BUR)
• Benefits of Single-Ply Over Metal Roofs
• Single Ply Disadvantages Compared to BUR 
• Single Ply Disadvantages Compared to Metal Roofs
• Types of Single-Ply Roofing
• EPDM (Ethylene Propylene Diene Monomer)
• PVC (Polyvinyl Chloride)
• TPO (Thermoplastic Polyolefin)

What Is Single-Ply Roofing?

The term 'single-ply' describes the method of installing just a single layer of roofing material onto the roof assembly. Single ply roofing was developed to replace built-up roofing (BUR), which was the most popular choice for more than a century. Unlike built-up roofs, which comprise multiple layers of asphalt and reinforcing fabric, single-ply roofs consist of a single, light, flexible layer - making installation both easier and safer.

A single ply membrane starts off as a liquid coating, but is typically combined with a nylon fabric reinforcing scrim, then cured and turned into a solid but flexible sheet.

These roofing sheets can be fully adhered, mechanically attached, ballasted, or wind-vented. 

• In fully adhered single ply roofs, the membrane is glued to the insulation layer beneath it.
• In mechanically attached single ply roofs, the membrane is fastened to the roof deck with mechanical fasteners.
• In ballasted single ply roofs, the membrane is loose-laid and held in place with gravel, pavers, or other ballast materials.
• In wind-vented systems, the membrane is laid over the entire roof like a ballasted system, but instead of securing it with ballasts, an air seal with valves uses wind pressure to hold the in place

The membrane's seams are then sealed to make the roof waterproof. Seaming methods include hot-air welding, heat induction welding, solvent welding, or self-adhesive seams. The edge of the roof is usually finished with a metal drip edge or custom fabricated coping cap.

These roofs are celebrated for their simplicity and speed of installation. They require fewer materials and labor than multi-layer roofs, which reduces the cost and time required for installation. However, they are just as effective at keeping out the elements.

The most common types of single-ply roofing membranes are Thermosets (like EPDM) and Thermoplastics (like PVC and TPO). Each has its own set of characteristics, advantages, and disadvantages, which we will explore in detail later in the article.

Single-Ply vs Built Up Roofs & Metal Roofs

Single ply roofing systems comprise the vast majority of commercial roofs, with TPO alone making up 40% of all flat roofs. Why did they become so popular, almost completely replacing the previously popular built-up roofing (BUR) systems? 

For a few reasons:

Single Ply Advantages Over Built-Up Roofing (BUR)

Lightweight: Single-ply roofing materials are significantly lighter than BUR systems. This reduces the stress on the building structure and makes it a viable option for both new constructions and roof replacements.

Ease of Installation: The installation of single-ply roofing is less labor-intensive than BUR, translating to faster completion times and lower labor costs. 
No noxious fumes. Laying asphalt on the roof is a messy, smelly process. Single-ply sheets eliminate this problem.

Performance: Single-ply roofing is exceptionally durable and resistant to the elements. It also generally outperforms BUR in terms of reflectivity, which can lead to energy savings.

Maintenance: Single-ply roofing systems require less maintenance compared to BUR, making them more cost-effective in the long run.

Benefits of Single-Ply Over Metal Roofs

Single-ply roofing also has some advantages over metal roofs.

Thermal Efficiency: Single-ply materials, particularly white-colored ones, are highly reflective and can significantly reduce the cooling costs during the hot months compared to metal roofs, which may absorb more heat.

Cost: Single-ply roofs are usually much less expensive than metal roofs.

Superior Thermal Insulation: A metal roof loses over 80% of its insulating properties at the points where the bottom of the roof panel touches the top of the purlin (part of the building structure) - the insulation gets compressed at these points. A single-ply roof, by contrast, uses a different kind of insulation that does not suffer from compression at the purlins.

Sound Insulation: Single-ply roofing materials offer better sound insulation compared to metal roofs, which can be noisy during heavy rain or hail.

While single-ply roofing systems are undeniably beneficial, they do carry disadvantages when compared with BUR, metal roofing, and roof coatings.

Single Ply Disadvantages Compared to Built Up Roofing

Fewer Layers of Protection: BUR systems, made from alternating layers of bitumen and reinforcing fabrics, can offer more comprehensive protection against leaks. If a single-ply membrane is punctured or damaged, water can easily infiltrate the roofing system, saturating and ruining expensive insulation and creating leaks.

Vulnerability to Mechanical Damage: Compared to the robust and multi-layered BUR, single-ply roofing systems are more susceptible to damage from dropped tools or traffic from maintenance personnel and can require more careful handling during installation.

Single Ply Disadvantages Compared to Metal Roofs

Lifespan: Metal roofs are renowned for their longevity, often outlasting single-ply roofing. While single-ply materials are durable, they may not match the lifespan of a well-maintained metal roof.

Resistance to Extreme Conditions: Metal roofs can withstand extreme weather conditions better than single-ply roofing. They're resistant to fire and some types can even resist high wind speeds.

Resistance to puncturing: The membrane of a single ply system is more susceptible to punctures and abrasions than metal. 

Overall, the shift towards single-ply roofing systems is a reflection of the roofing industry's aim to provide durable, cost-effective, and sustainable solutions that cater to the unique needs and concerns of various commercial buildings.

While single-ply roofing has seen considerable improvements over the years, it's essential to note that it's not a one-size-fits-all solution. Each type of single-ply roofing has its strengths and weaknesses, and the best choice depends on various factors such as the building's design, the local climate, and the budget available. We'll dive deeper into these considerations in the next sections.

Types of Single-Ply Roofing

Single-ply roofing, though encapsulating a broad classification, further diversifies into several types, each with its unique attributes, advantages, and disadvantages. In this comprehensive exploration, we will delve into the three primary types of single-ply roofing: EPDM (Ethylene Propylene Diene Monomer), PVC (Polyvinyl Chloride), and TPO (Thermoplastic Polyolefin).

1. Ethylene Propylene Diene Monomer (EPDM)

Ethylene Propylene Diene Monomer (EPDM) is a type of synthetic rubber recognized for its remarkable durability and adaptability. This membrane features a dark surface that effectively absorbs heat, rendering it an optimal choice for colder climates.

EPDM Advantages

EPDM roofing manifests resilience, boasting an exceptional resistance to UV radiation, weathering, and ozone. Moreover, its installation and repair procedures are relatively straightforward, lowering the overall lifecycle costs. It’s also environmentally friendly, as it’s designed to be recycled at the end of its lifespan.

Today's EPDM roof systems are to be recognized as one the best long-term roofing investments a building owner or facilities manager will make. They are a tried and true roof system.

EPDM Disadvantages

The standard EPDM's darker shade could lead to increased cooling costs in warmer climates, although there are lighter-colored variants available. An EPDM membrane can see surface temperatures of 180 degrees in the dead of summer. It's so hot that it will instantly blister the skin on your hands. 

A roof in the south that has a more aggressive angle from the sun with hotter ambient temperatures will overwork HVAC and chiller units causing them to fail prematurely and make them expensive to maintain and run. Fortunately, changing the color of the membrane from black to white is enough to avoid these problems.

EPDM Cost

EPDM is a solid, cost-effective solution that comes in between the more expensive PVC and the least expensive TPO.

For a more in-depth treatment of EPDM, check out our Complete Guide to EPDM.

2. PVC (Polyvinyl Chloride)

Polyvinyl Chloride (PVC) is a thermoplastic single-ply roofing membrane, known for its ability to withstand chemicals and waste products. This membrane can be heat-welded at the seams, enhancing its strength significantly.

PVC Advantages

PVC roofing systems feature excellent heat-reflective properties, making them suitable for hot climates. The primary advantage of PVC is its ability to withstand numerous industrial chemicals, including salt and jet fuel, making them an excellent choice for industrial environments, airports, and coastal buildings. 

PVC will also stand up to animal fats and by-products from restaurants and food manufacturing plants.

PVC is also a true Class-A fire rated product. When introduced to an open flame for a period of time the PVC material will immediately self-extinguish, never showing signs of a flame.

PVC membranes are often the single-ply of choice when installing roof top landscaping or live roof (green roof).

The PVC membrane is often trusted more so than TPO by the nations top architects, roof consultants, and specifiers.

PVC Cons

Despite their overall durability, PVC systems can be susceptible to punctures and tears. Moreover, the chemical plasticizers used in PVC membranes may leach out over time, potentially reducing the membrane's flexibility.

PVC Cost

The cost of PVC roofing can be higher than EPDM, mainly due to the quality of the product and the installation's complexity.

For a more in-depth treatment of PVC, check out our Complete Guide to PVC.

3. TPO (Thermoplastic Polyolefin)

Thermoplastic polyolefin (TPO) is another variant of thermoplastic single-ply roofing membranes. Like PVC, TPO is lightweight, flexible, and can be heat-welded at the seams for improved durability and waterproofing.

TPO Advantages:

TPO systems offer excellent energy efficiency due to their heat-reflective and energy-efficient properties, especially the lighter-colored versions.

TPO Disadvantages

While TPO generally performs well, it is not as chemical or fire-resistant as PVC, so it’s not a great choice for industrial applications.

TPO Cost

The cost of TPO roofing is the least expensive single-ply membrane, so it’s ideal for a tighter budget or if you have acres to roof on a large facility. 

For a more in-depth treatment of TPO, check out our Complete Guide to TPO.

The Upshot

A roofing decision is one you’ll have to live with for 15-20 years, so making a suboptimal decision is a real concern. Hopefully, with everything we’ve discussed in this article, you now have a good understanding of single ply roofing, and you’re one step closer to making the best decision for you. 

To tackle your roofing concerns and needs head-on, remember that expert help is just a call or email away. Don't let the fear of potential roofing issues keep you up at night. Set up a free 30 minute call with our experts, and let GIDEON provide you with the confidence in knowing your roof - and investment - is in good hands.