What is a Low-Slope/Flat Roof System?

July 17, 2012

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Flat roofs, often described as low-slope roofs or low pitched roof, are not entirely flat but have a slight pitch to allow water drainage. Roof slope is measured by the slant of the roof, and a low-slope roof has a slope of less than 3-in-12, meaning it goes up less than 3 inches vertically for every horizontal foot. Unlike steep-slope roofs that rely on gravity to shed water, low-slope roofs must form a watertight, monolithic membrane that stays sealed all the way to the drains or edge.

Choosing the Perfect Flat Roof System

Your commercial property in South Florida deserves nothing less than the best protection from the frequent rainstorms and scorching sun. A reliable and durable flat roof system is essential to safeguard your investment. In this blog, we will explore three popular types of flat roof systems: Built-Up Roofing, Modified Bitumen Roofing, and Single Ply Roofing. Each system has its unique advantages and considerations, making it crucial to choose the right one based on your property's specific requirements.

Built-Up Roofing (BUR)

Built-Up Roofing, fondly known as the "tar and gravel" roof, has stood the test of time as a traditional choice for low-slope roofs. This reliable system involves layering multiple sheets of roofing felt, or "tar paper," bonded together with hot asphalt or coal-tar pitch (bitumen). The result is a robust and watertight membrane that is further protected by a coating or gravel embedded in hot bitumen.


  • Proven historical performance

  • Excellent resistance to wind, freeze-thaw cycles, and UV radiation

  • Long-lasting and durable


  • Limited flexibility compared to newer systems

  • Environmental concerns due to the use of crude oil-based products

  • Occasional cost-prohibitive nature due to fluctuations in crude oil prices

Modified Bitumen Roofing (Mod Bit)

Modified Bitumen Roofing

Modified Bitumen Roofing is an evolution of traditional asphalt roofing, offering increased flexibility by chemically modifying the asphalt. It is constructed over a sturdy polyester or fiberglass mat for added strength. MB roofs excel in waterproofing, making them an excellent fit for South Florida's rainy climate. The system offers versatile application methods and various top-surfacing options, including "Cool Roofing" choices that reflect sunlight, reducing heat absorption and energy costs.


  • Proven track record of performance

  • Superior waterproofing capabilities

  • Versatile application methods

  • Energy-efficient "Cool Roofing" options available

  • High tensile-strength and durability

  • Available as part of a fire, wind, and/or hail rated roofing system

  • Competitive life-cycle cost

  • Long-term warranties available

Single Ply Roofing

Single Ply Roofing

Single Ply Roofing is a modern and popular choice for low-slope roofs due to its efficiency, ease of installation, and cost-effectiveness. This system consists of a single, continuous membrane covering that is either mechanically attached or adhered to the roof deck. The three primary types of single ply roofing materials are Thermoplastic Olefin (TPO), Polyvinyl Chloride (PVC), and Ethylene Propylene Diene Monomer (EPDM).


  • Seamless and continuous membrane reduces the risk of leaks

  • Lightweight and easy to install

  • Resistant to pools of standing water

  • Excellent UV resistance

  • Energy-efficient options available

  • Cost-effective and low maintenance

  • Suitable for various commercial roofing applications


Selecting the perfect flat roof system for your South Florida commercial property is a crucial decision that requires careful consideration of performance, durability, cost, and environmental impact. Built-Up Roofing, Modified Bitumen Roofing, and Single Ply Roofing each offer unique advantages, and consulting with a reputable commercial roofing contractor is essential to make an informed decision.

At Best Roofing, we understand the roofing needs of South Florida properties and can help you choose the right flat roof system that ensures the longevity and protection of your property. Our experienced team of professionals will work closely with you, from consultation to installation, providing unmatched service and exceptional results. Contact us today to schedule a roofing assessment and discover the best flat roof system for your commercial property in South Florida.