13 Flat Roofing Terms You Need To Know

Commercial and residential roofing encompasses a wide vocabulary of terms which are useful for property owners to understand. The more familiar you are with the following 13 terms, the easier it will be communicating your roofing options with an expert.

13 Terms

BUR (Built-up Roofing) – BUR is a commonly used asphalt-based material for low-sloped roofs. It comprises alternating layers of fabric and asphalt with an aggregate finish. This type of membrane known as “tar and gravel” has been used in roofing systems for over a century.

TPO (Thermoplastic polyolefin) – TPO has similar properties to PVC, yet is more affordable. Another TPO flat roof benefit is the warranty usually lasts longer than PVC. For these reasons, it’s a fast growing commercial roofing solution, using a single layer of synthetics and rubber as a membrane for flat roofs. TPO offers stable protection and deflects ultraviolent (UV) rays.

Modified Bitumen – MB is a type of roofing based on asphalt, similar to BUR and is commonly used for commercial buildings with low-slope roofs. It’s actually considered a modern version of BUR. Not only is MB waterproof, other advantages include it’s easy to repair, resistant to tearing and energy-efficient.

Flashing – As a form of weatherproofing, flashing is made of thin but sturdy strips designed to create barriers around chimneys, windows and doors. It essentially adds a protective seal for preventing air and water from getting into a building. Durable materials used for flashing include aluminum, stainless steel and copper.

HVAC – Heating, ventilation and air conditioning systems are referred to as HVAC. It’s an integral component to any residential or commercial structure, as it regulates temperature and provides comfort. These systems can also affect indoor air quality. Air filters must be cleaned and replaced regularly to ensure good performance and durability of the entire system.

R-Value – This insulation metric is used to measure thermal resistance per unit area to determine flow of heat performance. R-value is added to material layers for walls, windows and doors to improve performance. This value is determined by dividing the warm and cold temperature differences of the surface by the amount of heat flux within the barrier.

Substrate – In construction a substrate has a few different meanings. It’s commonly used to refer to a material surface, such as an underlying layer, in which other substances are added. It can also be a material from the ground such as sand or materials which make up a building’s foundation. A substrate is often the base material for a protective layer.

Underlayment – Usually made of waterproof material, an underlayment is a secondary roofing layer installed on the roof deck. It’s typically underneath the top roofing layer such as shingles, serving as insulation.

Seam (between sheets of material) – A seam helps protect fasteners on a flat panel which snaps over another panel, as on a metal roofing system. Seams can lock panels together instead of using nails. Seams create tight connections in roofing layers to prevent air and water leaks. Standing seam metal roofs are among the most durable roofing solutions.

Storm Straps (Used for hurricane protection) – A storm strap is used to strengthen frames on a roof. They are designed to protect structures from inclement weather like tropical storms.

Single-Ply – This sheeting with a wide width is often used for low-slope roofs. It typically has fewer seams than asphalt-based rolled roofing systems and is much easier to install. It’s an economical solution for large commercial roofs. The three common membranes used for single-ply are TPO, EPDM and PVC.

Torch-down – Designed with modified bitumen, this roofing system includes layers of fiberglass installed with a flame torch. It’s used exclusively for flat or low-slope roofs. The roofing specialist heats the rolled layer of roofing material with a hand-held propane torch to attach it to the surface. It involves melting seams together, which creates a tight seal. A torch-down roof can expand or contract without cracking.

Felt – Roofing felt is made of either natural or synthetic materials with protective coating designed to resist water. The coating is commonly made of asphalt. The National Roofing Contractors Association (NRCA) recommends felt as a waterproof solution, which many cities require in their building codes. This protective layer is installed between the roof deck and the top layer. Felt helps prevent damage caused by water or ice.


Residential and commercial property owners should have their roofs inspected on a regular basis to keep maintenance costs under control. Contact us at Alan’s Roofing to get a free quote for your roofing needs. We serve Central Florida, Orlando, Tampa and beyond.