The Different Types of Flat Roofing
An Independent Roof Inspector's Guide
Flat roofing systems are a critical component of both commercial and residential buildings, providing protection from the elements while also contributing to the building's aesthetic and functional design. As an independent roof inspector, I have assessed numerous flat roofs over the years and have gathered valuable insights into the various materials used, their life expectancies, and their performance against wind and hail, which are crucial factors for building owners to consider. This post aims to educate on the different types of flat roofing materials, focusing on their longevity, and resilience to wind and hail, using available manufacturer data where possible.
1. EPDM (Ethylene Propylene Diene Monomer)
Life Expectancy: EPDM, commonly known as rubber roofing, can last between 20 to 35 years. Its durability is attributed to its robust resistance against UV rays, temperature fluctuations, and general wear and tear.
Wind Ratings: EPDM roofing systems can withstand wind speeds up to 120 mph, depending on installation quality and maintenance.
Hail Limits: Hail resistance varies, but generally, EPDM can handle hail up to 1.5 inches in diameter without significant damage.
2. TPO (Thermoplastic Polyolefin)
Life Expectancy: TPO roofs are expected to last about 15 to 25 years. Their high reflectivity contributes to less thermal expansion stress over time.
Wind Ratings: These roofs are designed to resist winds of up to 110 mph, though specific products may offer higher ratings.
Hail Limits: TPO materials are typically tested for hail up to 1.25 inches, making them a sturdy option for areas with moderate hail exposure.
3. PVC (Polyvinyl Chloride)
Life Expectancy: PVC roofing has a life span of 20 to 30 years, thanks to its chemical resistance and ability to withstand ponding water.
Wind Ratings: PVC can effectively handle wind speeds exceeding 115 mph, with some products rated even higher.
Hail Limits: It can resist hail stones up to 1.5 inches in diameter, due to its tough, flexible membrane.
4. Modified Bitumen
Life Expectancy: The life expectancy of modified bitumen roofing systems ranges from 10 to 20 years, depending on the type and quality of the installation.
Wind Ratings: Modified bitumen roofs are capable of withstanding wind speeds up to 90 mph.
Hail Limits: The material can sustain hail impacts of up to 1 inch in diameter, with performance varying by specific product formulations.
5. Built-Up Roofing (BUR)
Life Expectancy: BUR, or tar and gravel roofing, can last 15 to 30 years, with durability depending on the number of layers and maintenance.
Wind Ratings: These systems are designed to cope with wind speeds of up to 100 mph, depending on the application method and anchoring.
Hail Limits: BUR roofs can generally withstand hail stones up to 2 inches in diameter, benefiting from the protective layer of gravel.
Conclusion
When selecting a flat roofing material, it is important to weigh the material's life expectancy against its resilience to environmental factors like wind and hail. Each material offers a unique set of advantages and limitations. Proper installation and regular maintenance are critical to maximizing a roof's lifespan and performance. As an independent roof inspector, my advice to building owners is to consult with experienced roofing professionals to choose the best material for their specific needs, considering the local climate and the building's structural requirements. Ensuring your roof is equipped to handle the challenges of wind and hail will contribute significantly to the longevity and integrity of your building envelope.