Wordogram for roofing

Top 24 Commercial Roofing Terms Explained

It’s true that the commercial roofing industry uses a lot of technical terminology that our customers probably are not familiar with. And we never want you to feel confused by specific terms we may mention as we give inspection reports or talk with you about problems on your commercial building’s roof.

That’s why we’re taking this opportunity to define 24 terms that we often use, but also commonly receive questions about here at Heidler Roofing.

Many have to do with various roofing materials. Some are simply abbreviations we use or words you’ve heard before, but that have different meanings in our industry lingo. Let’s take a closer look.


This term refers to granular mineral-based material, aka stone, rock, and/or gravel that’s been crushed or broken down into small pieces. In the commercial roofing industry, aggregate is used as a surfacing material or ballast (see next definition) for certain roof systems.


Ballasted roof systems employ loose aggregate material as weight (ballast) to hold the roof membrane in place instead of glues or other fasteners. The aggregate’s mass and the force of gravity are strong enough to keep the roof leak-free and protective for many years. While these roofs are no longer newly installed very often, they are still common on commercial buildings throughout Heidler Roofing’s service area, and our skilled craftsmen are very experienced with caring for them.

BUR/Built-up Roofing

BUR is the shorthand name we often use to refer to Built-up Roofing, which uses 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. Often seen on older commercial buildings with low-slope roofs, BUR has been in use for 120+ years. It is still considered one of the most cost-effective roofing systems, and it continues to be installed today.

Cover Board

Cover board is used as an insulation board in certain roofing systems, such as single-ply membrane systems, where a barrier is needed between the roof deck and the membrane. It is a substrate (see definition below) to which a membrane is adhered, but it also offers strong protection against destructive forces like hail and external fires. It strengthens a roof to prevent damage from foot traffic, as well, so you don’t have to worry about workers or others walking around on your roof.


Think of the term “elastic.” Elastomer is a material that can rapidly return to its original shape and dimensions after being stretched.


EPDM is an abbreviation for the chemical name of the single-ply rubber material used in many flat-roofed commercial buildings today — Ethylene Propylene Diene Monomer. EPDM roofing systems may also be called Thermoset systems, and these roofs are durable, versatile, and easy to install compared to many others. The term “Thermoset” means that the material cannot be reshaped by heating, and so it is resistant to thermal stress (defined below).


In the roofing world, exposure refers to the portion of the membrane that is not overlapped by a ply or course next to it. That is, the top layer of roofing material exposed to the elements after being installed is said to be the exposure.


Used in the creation of BUR systems, felt is a fiber-based, flexible sheet material meant to be layered. Felt fibers can be made from a wide variety of components including glass, polyester, wood, or even vegetable matter. Felt is absorbent and can be saturated or coated with materials like tar, asphalt, or bitumen for waterproofing.


Not a verb or action word in the roofing industry! Flashing refers to components used to weatherproof and/or seal the edges of roof systems at places where the covering ends (the edge of the roof) or is interrupted, such as at drains, valleys, expansion joints, or around rooftop equipment (see HVAC) and skylights.

Galvanized Steel

When steel is galvanized, it means that it has been coated with zinc to make it more resistant to corrosion – the iron in steel will rust if not sealed with a coating. Metal roofing may be made of galvanized steel, or it may be made of higher-cost aluminum.


These letters stand for Heating, Ventilation, and Air Conditioning. What does that have to do with roofing? Because this equipment is often located on the roofs of commercial buildings, roofers have to work around it. Leaks can often form around places where HVAC equipment is installed, as well, since it connects to system components inside the building through the roof’s structure.

Ice dam

This is the name for ice formations at the transition between warm and cold roof surfaces. Ice dams form when previously melted snow and ice refreezes during winter. Ice dams need to be prevented, as they commonly back up under roofing materials, which leads to leaks inside your building.

IBC – International Building Code

A model set of building standards published by the International Code Council (ICC), the IBC applies to all construction except low-density residential buildings (detached one and two-family dwellings and townhomes).


The flexible or semi-flexible roof covering material that primarily waterproofs a roof system. A membrane may be made of a single material or several materials laminated together.


An advanced metalworking technique that involves shaping and smoothing sheet metal over a stake. While this is more of a specialty roofing term, commercial roofs can also be specialty roofs that require care and repair.

Preventative Maintenance

This term refers to the act of getting more useful life from your commercial building’s roof by being proactive in caring for it to prevent problems. Here at Heidler Roofing, we offer customized maintenance plans to suit your budget and keep your roof in great condition. Plans include a thorough inspection process.


If you’ve ever shopped for insulation for your home or commercial building, you’ve heard this term, and you know that the higher the R-Value number, the better. This is because the term refers to thermal resistance, or the measure of a material’s resistance to heat flow. In practical application, R-Value denotes the specific thickness of an insulating material or construction type.

Single-ply membrane

Roofing membranes that are applied in one layer only are known as single-ply membranes. The EPDM systems we talked about above, as well as thermoplastic systems (defined below), are commonly single-ply membranes.


This term refers to the surface on which roofing or waterproofing membranes are applied. The term may refer to the structural deck of the roof, an underlayment, or a cover board (as defined above), depending upon the roofing system used.  Read about the difference between roof membranes vs substrates.

Thermal Stress

As external temperatures naturally change throughout the seasons and even day-to-day, your roof system will expand and contract. Over time, this causes stress to the materials as they age, and will eventually lead to damage. Some roofing systems are more resistant to thermal stress than others.

Thermoplastic/TPO & PVC systems

If a substance or material is thermoplastic, it means that, by design, it becomes soft when heated and hardens as it cools. TPO, which stands for thermoplastic polyolefin, and PVC, which stands for polyvinyl chloride, are both materials that have this quality. TPO and PVC weather well and are resistant to UV light, punctures, and many chemicals, including oils, animal fats, and bacteria. These systems are great for restaurants and other businesses that vent oils to the exterior.


A felt or sheet material that is installed between a roof deck and roof covering (most often in steep-slope roofs) is referred to as underlayment. Its purpose is to separate a roof covering from the structural deck of the roof and provide secondary weather and water protection within a roofing system.


It may sound strange, but all buildings need to “breathe” and exchange indoor and outdoor air. Roof vents are openings or devices that permit air to exit an enclosed structure. These vents must allow air and vapors to escape, but must not allow moisture to infiltrate the structure.

Water Infiltration

In short, water infiltration equals roof leaks. If water or moisture is infiltrating, or getting into, your commercial building, you may have a major problem on your roof that requires attention right away. Our Leak Squad is ready to help with expert repairs.

Have questions about a term we didn’t define, orneed help diagnosing problems with your commercial building’s roof? Heidler Roofing is here to help. Get in touch today and experience our legendary service.