Chapter 2: Commercial Roof Types: What to Know About Different Systems

There’s more to commercial roofing than just white or lighter colored roofs vs. black, non-reflective ones. A wide range of different materials and systems are available to choose from when installing a new commercial roof or refurbishing your building’s existing flat or low-slope roof.

As part of our new post series, your ultimate guide to commercial roofing is right here on our blog to help you learn more about what it takes to properly maintain commercial roofs and keep them working hard to protect your business.

Today we’re offering a closer look at what material and roofing system options are out there for building owners to consider. The architecture and unique needs of a particular building often dictate what type of roof will be best, but an owner’s budget, local weather patterns and climate in the building’s location, and even energy efficiency considerations help guide professional roofing contractors like us here at Heidler Roofing in our recommendations for the most robust roofing choices.

What are the Different Types of Flat and Low-Slope Roofs?

In short, the most popular types of flat and low-slope commercial roofing systems are:

  • Built-Up Roofing (BUR)
  • Modified Bitumen (MB or “Mod Bit”)
  • Single-Ply Membranes – TPO, PVC, and EPDM/Thermoset materials
  • Metal Roofing
  • Less Common Materials – Green/garden/vegetative roofs
  • Reflective Roof Coatings

Additionally, your building may incorporate a combination of materials and systems, or even be considered a specialty roof if your business happens to be in a historic building.

Let’s dive into what makes each type of system noteworthy.

BUR Systems

It’s appropriate to begin any discussion of commercial roofing types by starting with Built-Up Roofing or BUR systems. These roofs have been installed on American commercial buildings for more than 120 years, and they’re still a viable option today. BUR systems are cost-effective, long-lasting, and not difficult to repair, which makes them an attractive choice for building owners. Of course, they aren’t necessarily appropriate for all structures, and many newer membrane technologies offer advantages, such as reflectivity, that BUR does not.

But what is BUR? As we defined in our earlier post explaining top commercial roofing terms, Built-up Roofing utilizes layers of different materials to achieve durability and waterproofness. BUR is a continuous and semi-flexible membrane that consists of felt or fabric layers (called plies) alternated with layers of other materials like tar/bitumen and aggregate. These roofs are sometimes referred to as “tar and gravel” systems because of the material sandwiched between plies and the gravel/granules that are spread across the top.

Mod Bit Systems

Closely related to BUR, Modified Bitumen roofing is not quite as “historic” – it originated in Europe in the mid-1960s and caught on in North America in the mid-‘70s. It is an asphalt-based system, but it’s a little more versatile than BUR. It also doesn’t necessarily have to be hot-applied with torches, as technological innovations with these systems, like self-adhesive “cold process” sheets, eliminating the need for heating materials for proper installation.

Single-Ply Membrane Systems

As the name suggests, single-ply membranes are applied in one layer only. They can be made from a variety of materials, which are either thermoplastic (becoming soft when heated and more rigid as they cool) or thermoset (cannot be reshaped by heating/cooling). These systems are immensely popular today as they are generally on the easier end of the spectrum to install and can offer significant energy saving capabilities to building owners.

Thermoplastic Materials – TPO & PVC

TPO, which stands for thermoplastic polyolefin, and PVC, which stands for polyvinyl chloride, are both materials with a reliable thermoplastic nature. This allows membranes made from TPO or PVC to weather well and have good resistance to UV light (aka sunlight) and punctures.

Thermoplastic materials are also often an excellent choice for restaurants and other businesses that vent oily exhaust to the exterior, as they stand up well against many chemicals, including oils and animal fats, as well as bacteria.

Thermoset Materials

As external temperatures naturally change throughout the seasons and even day-to-day, all roof systems will expand and contract to some degree. Unfortunately, this is damaging to roofing materials over time, though thermoset membranes, like EPDM (Ethylene Propylene Diene Monomer), can handle this thermal stress with remarkable fortitude by the very nature of the material. EPDM cannot be reshaped by heating, and so it weathers well even in hot, sunny areas.

Metal Roofing

Often the winner on the environmental friendliness scale, steel and aluminum commercial roofing tends to last a long time and retain its performance capabilities as it ages. For instance, versus single-ply membrane roofing, metal roofs don’t become less reflective/energy-saving over time. They can, however, develop leaks around fasteners and seams (especially if not regularly maintained), which some other roofing systems do not rely on.

Metal roofing is considered a “green” choice because it is both made from recycled metals and is recyclable at the end of its service life. If environmental impact is important to you as a business or building owner, you’ll want to carefully consider your options with guidance from a professional contractor who can give you all the pros and cons of each material.

Garden Roofs

While it may seem that garden or green rooftops, which incorporate living vegetation, might be the most environmentally friendly roofing option, they are often prohibitively expensive to build. This means their positive effects are limited. Garden roofs also require building owners or managers to establish a care regimen for plants, which is often not in many business’s plans. Garden roofs can be extremely beautiful, however.

Reflective Roof Coatings for Restoration

If your building’s roof is older and experiencing some of the common problems that aging structures face, you’re probably curious about restorative coatings. There are a number of systems on the market that promise to stave off total roof replacement, and some of these solutions are quite good. They can add new reflectivity and stop leaks, and are certainly more wallet-friendly than replacing your building’s entire roof in most cases. Coatings can be applied to a range of roof surfaces, such as asphalt, gravel, metal, and single-ply membranes.

Heidler Roofing Cares for All Types of Commercial Roofing

Need help right away to stop a leak in your commercial building’s roof or just want to schedule an inspection to get a health check on your roof? Get in touch with us here at Heidler Roofing today and experience our legendary commercial roofing service throughout the Mid-Atlantic region.