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A-1's Helpful Commercial Roofing Glossary

Before you hire a commercial roofing contractor in Miami to install, repair, maintain, or replace your building’s roof, you need to understand the various terminologies used in the roofing industry. Check out this helpful commercial roofing glossary from A-1 Property Services.

Glossary of Commercial Roofing Terms


Aggregate refers to the surfacing or ballast for a commercial roofing system. Aggregate can be stone, rock, water-worn gravel, crushed stone or slag, marble chips, or crushed lava rock. Generally, an aggregate is applied on top of the final coating of asphalt to protect the roofing system from outside elements, including hail and ultraviolet (UV) rays.

BUR (Built-up Roofing)

Built-up roofing (BUR) is the most common roofing material for low-slope commercial roofs. It is composed of alternating layers of bitumen (asphalt) and reinforcing fabric, making it highly durable. The final product is finished with a layer of aggregate, such as gravel or stone.

TPO (Thermoplastic polyolefin)

Thermoplastic polyolefin (TPO) is another durable low-slope roofing material comprised of single-ply roofing membranes. Most TPO roofing systems are white in color and are mechanically fastened, fully-adhered, or self-adhered and welded at the seams. 


EPDM (short for “ethylene propylene diene terpolymer”) is a very durable synthetic rubber membrane that is mostly used in low-slope commercial buildings. The material is extremely lightweight, so the roof deck won’t require any kind of reinforcement. Since it’s made with a few seams, leaks are very rare; and, with proper installation, an EPDM roof can last up to 20 years. 


PVC roofing or polyvinyl chloride is comprised of a single-ply roofing material used on flat or low-slope commercial or industrial roofs. PVC is the third-most widely used synthetic plastic polymer, thanks to its durability and resistance to strong winds (up to Category 3 hurricanes). 

Modified Bitumen

Modified bitumen is a special type of asphalt roofing product that can be applied both in hot and cold temperatures. It’s often seen as the modern alternative to built-up roofs. This roofing system is inherently waterproof, and with proper installation, you can have the most moisture resistant roofing system. Modified Bitumen expands and contracts without losing shape, making it great for the Miami, Florida weather.

Roof Slope

A roof’s slope is a representation of the number of inches the roof rises for every 12 inches of horizontal “run.” So, a roof with a “4:12 slope” rises by 4 inches for every 12 inches of horizontal run. A roof slope can also be represented as a ratio, i.e. 4/12—or 1/3—slope. The terms “pitch” and “slope” are often used interchangeably in the roofing industry and mean the same thing.


Flashings are metal pieces which prevent water from seeping into your roof’s intersections, such as joints at vertical walls, valleys, or around roof penetrations such as vent pipes and chimneys.


It’s common to install the heating, ventilating, and air conditioning (HVAC) system for large commercial buildings on the roof. A proper rooftop HVAC installation will require the input of a professional roofer to ensure the roof’s structural integrity is maintained.


The R-Value is the measure of it’s a roofing material’s resistance to heat flow. Knowing the R-value of a roofing material is critical since many states and regions require that a roofing system exhibits some minimum amount of thermal resistance on institutional, commercial, or industrial buildings. Typical recommendations for exterior walls range between R-13 and R-23. For ceilings and attic spaces, the recommended R-values are R-30, R-38, and R-49.


The substrate is the surface upon which the roofing material or waterproofing membrane is applied. In roofing systems, the substrate could be the structural deck or insulation. 


Roofing underlayment refers to the water-resistant or waterproof barrier material installed directly onto your roof deck. Underlayment is typically applied under all other roofing materials as an additional layer of protection from extreme weather conditions. 


For metal roofs, a seam is a concealed fastening metal panel system with vertical legs and a wide, flat area in between the two supporting legs. You can have raised seams or vertical legs that leap over the surface of the panel’s flat face.

Storm Straps 

Storm straps are manufactured from galvanized steel. They attach to wall plates and trusses, giving your roof a strong hold against strong winds or hurricanes. A hurricane strap is especially important for wooden structures, helping them resist uplifts, sliding, overturning, or racking from strong winds during hurricanes.


Single-ply roofing systems comprise of flexible sheets of compounded plastic-derived products that are used on flat and low-sloped roofs. When properly installed, single-ply roofing systems offer more advantages over traditional flat roof materials, thanks to their strength, durability, and flexibility.


Torch down is just another name for Modified Bitumen. It is a rolled roofing material that comprises of a tough membrane that is embedded in a thick layer of asphalt. During the installation, the layer is “torched down” into position, hence the name. Overall, torch down roofing is durable and dependable.


Felt is an asphalt-impregnated roofing paper that is used to create a secondary, watertight barrier between various roofing products and the roof deck.

Request a FREE Quote from a Certified Commercial Roofing Contractor in Miami

Having gone through this common commercial roofing glossary, it’s important to note that a commercial roof is as good as the quality of its installation. Always work with a reputable local roofer to get the most out of your commercial roof. A-1 Property Services has been offering high-quality commercial roofing services in Miami, FL since 2006. Contact us today for a free, no-obligation estimate for your commercial roofing needs. Call us today with questions, to learn about financing options or any questions or concerns at 786-386-1149

A-1’s Helpful Commercial Roofing Glossary