Why Do Commercial Buildings Have Flat Roofs?

As a business owner or manager, you may have noticed that most medium and larger commercial buildings have flat roofs. There are many reasons why flat roofs are a common option for commercial buildings. 

BRH Enterprises LLC is your trusted local roofing company in Mayville, WI, and the nearby areas. For a no-obligation estimate or to discuss your project with our professionals, feel free to call us today at (920) 249-4228.

*Please note, price ranges listed in this article may not reflect the final cost of your project. Prices are subject to change based on various factors such as local labor rates, material quality, and more. All costs established in this article are rough estimates based on average industry rates. 

Why Most Commercial Buildings Have Flat Roofs?

It is very common for large commercial properties to have flat roofs. This architectural choice isn’t random, as we’ve already mentioned, it’s based on some practical, economic, and functional reasons. Here, we will discuss why flat roofs are popular for commercial buildings.

#1 Cost-Effectiveness

Maybe the most compelling reason commercial buildings have flat roofs is cost-effectiveness. Flat roofs are comparatively more affordable to install on large structures than pitched roofing systems. 

Commercial buildings generally cover larger square footage, and installing pitched roofs would require extensive framing, more materials, and increased labor costs.

#2 Easier Installation On Large Structures

Installing a pitched roof on a small residential home is relatively simple, but attempting the same on a large commercial building would be impractical and potentially dangerous. 

As buildings increase in size, the complexity and challenges of constructing pitched roofs grow exponentially.

Flat roofs, by contrast, can be installed quickly and efficiently on structures of virtually any size. This ease of installation reduces construction timelines, allowing businesses to become operational sooner and minimizing disruption during roof replacements or repairs.

#3 Space For HVAC And Equipment Storage

Another important benefit of installing commercial flat roofs is the extra rooftop space they provide. Rooftop HVAC units, which are typically large and heavy, can be easily placed and maintained on flat roof surfaces. 

Flat roofs save valuable interior space that can be used for offices, manufacturing, or retail. They also eliminate the need for ground-level HVAC placement, freeing up exterior space.

This also reduces operational equipment noise inside the building and protects equipment from potential vandalism or damage. 

Also, other than HCAC units, flat roofs provide extra space for other equipment like satellite dishes, solar panels, and communication devices. 

#4 Energy Efficiency

Flat commercial roofs can be designed with energy efficiency as a primary consideration. White or highly reflective roofing materials can be used to resist damage from the sun’s harmful UV rays. These reflective surfaces reduce solar heat gain, keeping interior spaces cooler during hot weather and significantly reducing energy costs associated with air conditioning.

Many commercial flat roofing systems qualify for energy efficiency certifications and may help businesses earn tax incentives for environmentally friendly building practices.

The energy savings continue year after year, making flat roofs a nice long-term investment for cost-conscious business owners.

#5 Drainage Solutions

While it may seem counterintuitive, flat commercial roofs actually have sophisticated drainage systems. From a technical standpoint, no roof is completely flat — commercial “flat” roofs are designed with a slight slope to facilitate water drainage.

Commercial roofs have specialized systems to handle water runoff efficiently. These roofs often have internal drainage systems with strategically placed roof drains like scuppers that allow water to drain directly off the edge of the building. 

Also, these roofs are generally constructed with tapered insulation systems that create natural slopes toward drainage points. For removing water from larger roof surfaces, there are siphonic drainage systems that provide rapid water removal. 

#6 Additional Usable Space

Another benefit of flat roofs for commercial buildings is the extra space they provide, which can be used for many purposes other than HVAC installation.

Many businesses use their rooftops for gardens, employee break areas, recreational spaces, storage spaces, and even helicopter landing pads (for corporate headquarters or medical facilities). 

#7 Easier Maintenance and Access

Maintaining a commercial roof is very important for protecting your investment, and flat roofs provide significant advantages in this regard. Their accessible design allows maintenance professionals to walk safely across the surface to perform inspections, repairs, and routine maintenance.

This easy access means more thorough visual inspections are possible, and small repairs can be completed more efficiently. Regular maintenance is also less labor-intensive, and small problems can be identified and repaired before they get worse.

The practicality of working on a flat surface cannot be matched by pitched roofs, especially for large commercial structures.

#8 Durability and Longevity

Modern commercial flat roofing systems are engineered for exceptional durability and longevity. With proper installation and regular maintenance, many commercial flat roofing materials can last decades:

👉 Built-up roofing systems come with a lifespan of up to 30 years

👉 EPDM rubber membranes mostly last 20 to 30 years

👉 TPO and PVC single-ply membranes often last over 20 years

👉 Metal flat roofs can last 40 to 70 years or more

This lifespan makes flat roofs a long-term investment for commercial property owners, despite the need for more frequent maintenance compared to pitched roofs.

What Are Common Materials Used for Commercial Flat Roofs?

Choosing the right material for your commercial flat roof is very important for its performance, longevity, and cost-effectiveness over time. 

Each roofing system provides different advantages depending on your specific needs, climate conditions, and budget constraints. Here, we will take a look at the most common commercial flat roofing materials.

#1 EPDM (Ethylene Propylene Diene Monomer) 

EPDM is a synthetic rubber roofing membrane used in commercial applications throughout the world.

👉 Cost: $8 to $15 per square foot installed, making it one of the more affordable options.

👉 Lifespan: 20 to 30 years with proper maintenance.

👉  Efficiency: Available in black or white, with white EPDM offering better energy efficiency through solar reflection. Black EPDM absorbs heat, which can be beneficial in colder climates.

👉 Suitability: Excellent for large, open roof areas due to its availability in wide sheets (up to 50 feet), reducing the number of seams. 

EPDM is highly resistant to UV damage, ozone, and extreme weather conditions and is suitable for buildings in areas with significant temperature fluctuations due to its flexibility.

#2 TPO (Thermoplastic Polyolefin) 

TPO has become increasingly popular for commercial applications due to its balance of performance and cost.

👉 Cost: $9 to $20 per square foot installed.

👉 Lifespan: 15 to 25 years, depending on installation quality and environmental conditions.

👉 Efficiency: This flat roof material improves energy efficiency by reducing the amount of heat absorbed by the roof. Also, many TPO roofs meet Energy Star requirements.

👉 Suitability: Works well in various climates but works best in warmer regions where its reflective properties are the most beneficial. 

TPO is also resistant to dirt accumulation, algae growth, and many chemicals. Its seams are hot-air welded, creating strong bonds that resist water infiltration.

#3 PVC (Polyvinyl Chloride) 

PVC membranes have impressive durability and resistance to chemicals, making them the best option for some commercial applications.

👉 Cost: $10 to $20 per square foot installed, making it one of the more premium options.

👉 Lifespan: 20 to 30 years, with some manufacturers offering 30-year warranties.

👉 Efficiency: Highly reflective white surface that often exceeds Energy Star requirements for solar reflectivity.

👉 Suitability: PVC roofs are excellent for restaurants, manufacturing facilities, or buildings where the roof can be exposed to chemicals or grease. PVC’s chemical resistance prevents membrane degradation in these environments. The heat-welded seams create a watertight bond that outperforms many other roofing systems.

#4 Built-Up Roof (BUR)

BUR systems have been used for over a century and consist of alternating layers of bitumen (asphalt or coal tar) and reinforcing fabrics.

👉 Cost: $15 to $25 per square foot installed.

👉 Lifespan: 15 to 30 years, depending on the number of layers (plies) installed.

👉 Efficiency: Traditional BUR systems without reflective coatings have lower energy efficiency. However, modern BUR systems can incorporate reflective coatings or caps to improve energy performance.

👉 Suitability: Excellent for roofs with frequent foot traffic or mechanical equipment that could damage single-ply systems. The multiple layers provide exceptional durability and puncture resistance. BUR performs well in extreme weather conditions and offers excellent waterproofing capabilities.

#5 Modified Bitumen 

Modified bitumen combines the traditional BUR approach with modern polymer modifications for enhanced performance.

👉 Cost: $10 to $15 per square foot installed.

👉 Lifespan: 20 to 25 years with proper maintenance.

👉 Efficiency: It can be manufactured with a reflective surface or coated to improve energy efficiency. Modern modified bitumen systems provide improved UV resistance compared to traditional BUR systems.

👉 Suitability: It is a good option for cold climates because of its flexibility at low temperatures. The reinforced bitumen provides excellent flexibility, which makes it resistant to tearing. 

#6 SPF (Spray Polyurethane Foam) Roof

SPF roofing is a spray-applied system that creates a seamless, sturdy roof covering.

👉 Cost: $7 to $10 per square foot installed, plus additional costs for recoating every 10 or 15 years.

👉 Lifespan: 20 to 30 years when properly maintained with regular recoating.

👉 Efficiency: Spray polyurethane roofs provide great thermal insulation properties that reduce overall heating and cooling costs. The smooth application of this roofing system helps prevent thermal bridges and air leakage.

👉 Suitability: Best for buildings with complex roof shapes or numerous penetrations since the foam conforms to irregular surfaces. SPF roofs provide both insulation and waterproofing in a single system. It’s lightweight yet durable, making it suitable for various structural situations.

#7 Metal Roof

While often associated with sloped applications, metal roofs can be adapted for low-slope commercial applications.

👉 Cost: $5 to $15 per square foot installed for commercial applications.

👉 Lifespan: 40 to 70 years, making it one of the longest-lasting options available.

👉 Efficiency: Reflective coatings can make metal roofs highly energy efficient. Some metal roofs also qualify for energy efficiency tax credits.

👉 Suitability: Metal roofs are considered best for areas with heavy snowfall or frequent weather fluctuations. 

Metal roofs are fire-resistant, lightweight, and environmentally friendly (often made from recycled materials and being recyclable again at the end of its life). Standing seam metal roofs provide an excellent surface for solar panel installation.

Also Read: 5 Best Commercial Roofing Companies In Mayville

Get Professional Commercial Roofing Services In Wisconsin

At BRH Enterprises LLC, we are your local roofing company in Mayville and the surrounding areas of Wisconsin. Our team understands the importance of seamless and functional roofing systems in commercial properties. 

We only use high-quality materials and industry-certified practices to ensure that your roof maintains its performance and appearance throughout its expected lifespan. 

Our team will come out, inspect your roof, and give you straight answers about what it needs. Whether it’s a small fix or something bigger, we’re here for you. To schedule your free roof inspection or for a no-obligation conversation with our roofers, feel free to call us today at (920) 249-4228.