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15 Helpful Commercial Roofing Terms You Need To Know

15 Helpful Commercial Roofing Terms You Need To Know

The commercial roofing industry has many technical terms customers may find confusing. To help you understand your roofer and make informed decisions regarding your roofing project, check out this commercial roofing glossary.

BUR (Built-up Roofing)

BUR is a continuous, semi-flexible roof membrane which uses layers of different materials to achieve waterproofness and durability. BUR systems typically consist of layers of felt or reinforcing fabrics (known as plies) alternated with layers of bitumen, which can be tar, asphalt, aggregate, or cold-applied adhesive. BUR systems are generally surfaced with bituminous materials, mineral aggregate, or granule surfaced roofing sheet. Built-up roofing is versatile, durable, water-resistant, and energy-efficient.

TPO (Thermoplastic Polyolefin)

TPO is a single-ply roofing membrane made up of synthetics and reinforcing scrim. TPOs are often compounded with fillers to provide a good balance of impact resistance and stiffness, as well as increased Heat Deflection Temperature and better dimensional stability. TPO roofing systems have gained widespread industry acceptance due to resistance to UV rays, chemical, and ozone exposure.


Commonly known as ‘rubber roof’, EPDM stands for Ethylene Propylene Diene Monomer. It is a single-ply rubber material and is extremely versatile, durable, and easy to install and repair. EPDM is primarily made from propylene and ethylene, which are derived from natural gas and oil. It is available in black and white and is sold in a variety of thicknesses and widths.

The membranes are highly durable and have a high resistance to hail, wind, thermal shock, UV radiation, and extreme temperatures, ensuring the roof will remain watertight for years to come.


PVC is a single-ply roofing membrane made from two layers of polyvinyl chloride where polyester is added as reinforcement between the layers. The layers also include additives making the material durable, flexible, UV stable, and environmentally sustainable. By adding a layer of acyclic coating, a PVC roof is made repellent to dust and is also reflective.

Modified Bitumen

Modified bitumen is composed of asphalt and modifying polymer blends. It’s then reinforced with fiberglass or polyester fiber to increase strength and durability. The two main types of modified bitumen are APP (atactic polypropylene) and SBS (styrene-butadiene-styrene).  SBS increases the membrane’s flexibility while APP increases the aging ability. Modified bitumen roofs are able to withstand harsh exposure to extreme elements.


Flashing refers to pieces of impervious material placed at the edges of roof systems to prevent the passage of water into the structure through a joint or penetration. Roof flashing is typically installed at the penetrations, perimeters, adjoining walls, and around skylights, vent pipes, drains, valleys, dormers, and HVAC.


HVAC stands for Heating, Ventilation, and Air Conditioning. Industrial strength HVAC systems are usually installed on top of commercial buildings and connect to system components located inside the building through the roof. This creates openings roofers must seal to prevent leaks.


R-Value refers to a material’s ability to resist conductive heat flow through it. When it comes to commercial roofing, the higher the R-value, the more insulation the material provides by allowing little heat to transfer between inside and outside of the building.


A roof substrate refers to the surface upon which other roof components, such as insulation, vapor control layers, and roof finishes are applied. It can be an underlayment, a roof deck, a cover board, or a complete preexisting roof system.


This refers to a waterproof or water-resistant material installed directly onto the roof deck and under all other roofing materials. There are three main types of roofing underlayment: Rubberized asphalt, asphalt-saturated felt, and non-bitumen synthetic. Roofing underlayment plays the primary role of sealing the structural deck of the roof and providing an added layer of protection from water and wind intrusion.


A joint formed when two sheets or types of materials join or overlap. Seams can be made or sealed by hot-air welding, adhesive bonding, solvent welding, or the use of adhesive tape and sealant.

Storm Straps

A storm strap is a connector used to strengthen a roof structure (specifically wooden framed roofs). The straps are generally made of stainless or galvanized steel and designed to protect the roof from storms, resisting uplifting, overturning, sliding, and racking. They are also known as hurricane ties, brackets, anchors, or clips.


This is a roofing membrane applied in one layer only. It’s a flexible sheet of compounded synthetic materials which can be ballasted, chemically adhered, or mechanically fastened to create a layer of protection on commercial facilities. Single-ply roofing systems are highly flexible, strong, and durable. The EPDM, PVC, and TPO systems defined above are common single-ply membranes.


Also known as torch-on roofing, torch down is a type of roof installed using an open-flame propane torch. Sheets of modified bitumen membranes are placed on a roofing surface and heated to ensure they adhere to the surface. This type of roofing may feature two layers or three layers of modified bitumen stacked and adhered together to ensure the integrity and waterproofness of the roof. Torch down roofing has a high tolerance to heat and cold.


Felt is a fiber-based, flexible sheet material which adds a layer of protection in BUR systems. Felt fibers can be made from a range of components, including wood, polyester, glass, or vegetable matter. It is absorbent and can be saturated or coated with tar, bitumen, or asphalt for waterproofing.

To learn more about these and other commercial roofing terms or to schedule an inspection for your commercial roof in Atlanta, contact Echols Home Improvements today. We work with the industry’s top roofing material manufacturers and are committed to getting the job done right the first time.

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