Why Do Commercial Buildings Have Flat Roofs

Why Commercial Properties Have Flat Roofing

Commercial buildings are often distinguished by their distinctive flat roofs, a design element that is both practical and aesthetically pleasing. This architectural choice is not merely a matter of style; it reflects a range of functional considerations that suit the unique needs of commercial properties.

In this article, we will explore the reasons behind why flat roofs are a common choice for commercial buildings, delving into the structural, practical, and economic factors that make this design so popular.

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What is a Flat Roof?

It’s important to note that a flat roof is not completely level. It’s helpful to think of them as a “low-slope” roof. A roof can be identified as “flat” if it has a tilt of 10 degrees or less.

A subtle incline is important for water drainage and prevents the accumulation of rainwater, which could lead to damage over time. The definition of a flat roof, therefore, is more about its appearance than its literal flatness.

The materials used in commercial flat roofs are chosen for their durability and suitability for low slopes. Common materials include Thermoplastic Olefin (TPO), Polyvinyl Chloride (PVC), Ethylene Propylene Diene Monomer (EPDM), built-up roofing (BUR), modified bitumen (mod-bit), and metal.

Each of these materials offers unique benefits and drawbacks for your commercial flat roof, which we will explore in the following sections.

Common Materials Used for Commercial Flat Roofing

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TPO (Thermoplastic Olefin)

TPO is a single-ply roofing membrane that has gained popularity in the roofing industry for its exceptional heat-reflective properties and energy efficiency. This lightweight roofing material is made from a blend of polypropylene and ethylene-propylene rubber.

TPO stands out for its ability to reflect UV rays, significantly reducing the cooling costs for a building. Because of its many benefits, such as cost-effectiveness and performance, it is favored in commercial construction. The material is also resistant to mold growth, dirt accumulation, tears, and punctures.


  • • Cost-effective
  • • Resistant to UV rays, chemical exposure, and ozone
  • • Reflective surface reduces cooling costs


  • • Relatively new in the market; long-term performance is still being evaluated
  • • Installation quality varies

Estimated Cost:

  • • Moderate

TPO roofing’s flexibility makes it adaptable to various roof styles, and it can be installed in different ways, including mechanically attached systems, ballasted systems, or fully adhered systems. TPO's energy efficiency and eco-friendly properties, combined with its durability, make it a top choice for commercial flat roofs. If you already have a TPO roof, check out our article about TPO roofing maintenance for more information.

Read More: Is TPO a Good Roof?

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PVC (Polyvinyl Chloride)

PVC roofing, made of Polyvinyl Chloride, is a highly durable single-ply thermoplastic material that has been a staple in the roofing industry for decades. Known for its strength and longevity, PVC roofing is composed of two layers of PVC material with a polyester reinforcement scrim in between.

The top ply contains additives that make the membrane UV-resistant, while the bottom ply is typically darker and absorbs heat. PVC roofs are highly resistant to chemical exposure, fire, and punctures, and they have a high tensile strength, which makes them less likely to crack or split.

This type of commercial flat roofing is particularly beneficial for restaurants and other businesses that emit oils and fats through their ventilation systems, as PVC is resistant to these substances.


  • • Resistant to fire, chemicals, and wind
  • • Energy-efficient due to its reflective properties
  • • Long lifespan when properly installed


  • • Higher cost compared to other materials
  • • Requires skilled installation

Estimated Cost:

  • • High

PVC is worth the investment thanks to being highly energy efficient due to its reflective properties. You’ll reduce your cooling costs, and since it is also recyclable at the end of its lifespan, it appeals to anyone looking for a more environmentally-friendly roofing option.

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EPDM (Ethylene Propylene Diene Monomer)

EPDM is a synthetic rubber roofing membrane renowned for its durability, versatility, and cost-effectiveness. It is made from a mixture of ethylene and propylene, two compounds derived from oil and natural gas. EPDM is particularly noted for its ability to withstand extreme weather conditions, including temperatures that range from scorching heat to freezing cold.

Its elasticity allows it to expand and contract without losing shape or cracking, making it ideal for a wide range of climates. The installation process of EPDM flat roofing is relatively straightforward and can be conducted with adhesive, mechanical fasteners, or ballasting.


  • • Excellent resistance to weathering, UV radiation, and temperature extremes
  • • Flexible and easy to install
  • • Environmentally friendly and recyclable


  • • Aesthetically less appealing
  • • Can be punctured by sharp objects

Estimated Cost:

  • • Moderate

EPDM commercial flat roofing has a long lifespan, typically lasting over 20 years with proper maintenance, and its low lifecycle costs make it a popular choice for commercial buildings. Its black color helps in absorbing heat in colder climates, but it can also be coated with a white layer to enhance its reflective properties in warmer regions.

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Built-Up/Mod-Bit (Modified Bitumen)

Built-Up Roofing (BUR) is a traditional roofing system that has been used for over a century. It involves the application of multiple layers of bitumen and reinforcing fabrics that create a finished membrane. These layers are typically made of asphalt, coal tar, or cold-applied adhesive. The top surface is usually covered with a layer of gravel or stone to provide protection from the sun and weather.

On the other hand, Modified Bitumen (Mod-Bit) is an enhancement of the BUR system, which incorporates polymer-modified bitumen sheets, vastly improving flexibility, strength, and durability. These sheets are factory-fabricated and can be applied using various techniques like hot-mopping, torch-applied, self-adhered, or cold-process adhesives. Mod-Bit systems are known for their resistance to foot traffic, punctures, and tears. They also offer improved elasticity and flexibility at lower temperatures compared to traditional BUR.


  • • Excellent waterproofing capabilities
  • • Durable and resistant to foot traffic
  • • Provides good insulation


  • • Installation can be messy and fume-intensive
  • • Heavy; may require reinforcement of the roof structure

Estimated Cost:

  • • Varies based on layers

Both BUR and Mod-Bit systems are valued for their multi-layer protection, making them highly reliable and durable roofing choices for commercial buildings. If you’re looking to invest in a Built-Up/Mod-Bit roofing system, please contact the experts at LOA Construction today!

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Metal Roofing

Metal roofing for commercial flat roofs, typically involving panels or tiles made from metal, offers a distinctive combination of durability, longevity, and aesthetic appeal. The most common metals used in this type of roofing are aluminum, steel, copper, and zinc, each offering unique benefits.

Metal roofing panels are known for their strength and ability to withstand extreme weather conditions, including high winds, heavy snow, and even fire. The metal's natural properties allow it to reflect solar radiant heat, which can reduce cooling costs by 10-25%. Its longevity is another significant advantage, with metal roofs often lasting 40-70 years, depending on the material.


  • • Long lifespan and extremely durable
  • • Fire-resistant and energy-efficient
  • • Can be recycled at the end of its life


  • • More expensive initial investment
  • • Requires specialized installation

Estimated Cost:

  • • High

Additionally, metal roofing is environmentally friendly, as most metal roofs contain 25-95% recycled content and are 100% recyclable at the end of their service life. While the initial cost may be higher than some other roofing materials, the long-term savings in maintenance and energy costs make metal roofing an economical choice for commercial buildings. Furthermore, the sleek appearance of metal roofing can be customized in terms of color and style, allowing for aesthetic flexibility in architectural design.

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Flat vs Pitched Roofs

While flat roofs are a common sight on commercial buildings, pitched roofs are more typical in residential structures. The key difference lies in their slope. Pitched roofs have a noticeable incline, which aids in water runoff and provides additional attic space or vaulted ceilings. In contrast, flat roofs offer a more minimalist aesthetic and are easier to access, making them ideal for housing equipment like HVAC units.

Each type has its advantages. Pitched roofs offer better water drainage and are traditionally seen as more aesthetically pleasing in residential settings. On the other hand, flat roofs are more cost-effective, easier to maintain, and provide usable outdoor space for commercial buildings.

Newly Replaced Commercial Flat Roof

Why Choose a Flat Roof for Your Commercial Building?

Choosing a flat roof for a commercial building is a decision influenced by multiple factors.

First, flat roofs are generally more cost-effective compared to pitched roofs. This cost efficiency is not just in terms of initial installation but also extends to long-term maintenance and repairs. Read more in our article here about flat roof repair.

The simpler design of flat roofs means fewer materials are often required, and the ease of access simplifies the process of installation, inspection, and subsequent repairs.

Another significant advantage of flat roofs is the additional space they provide. This space can be utilized for various purposes that might not be feasible with pitched roofs. For instance, it can house essential equipment like HVAC systems, solar panels, or satellite dishes in a more secure and less obtrusive manner. Additionally, this space can be transformed into a recreational area, such as a rooftop garden or a patio, providing a unique amenity that can enhance the value and appeal of the building.

Ease of inspection and maintenance is another key factor in choosing a flat roof. The flat surface allows for safer and more straightforward access for routine checks and repairs. This accessibility is crucial in ensuring the longevity of the roof, as regular maintenance can prevent minor issues from developing into significant problems.

Contact Us for a Commercial Flat Roof Installation

For businesses in the Austin, TX area, LOA Construction offers professional services for flat roof installations, replacements, repairs, and maintenance. With a focus on quality and customer satisfaction, LOA Construction ensures that your commercial building's flat roof is expertly handled, from initial installation to ongoing maintenance.

Contact LOA Construction today for reliable and professional flat roofing solutions tailored to your needs. We serve Austin, Houston, San Antonio, and the Belton, Temple, Killeen area. Look no further than our expert team for your commercial flat roof installation!

Environmental Considerations for Austin Roofs

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