Why Do So Many Commercial Buildings Have Flat Roofs

Why Do So Many Commercial Buildings Have Flat Roofs?

As a business owner looking to construct a new commercial building, you may be wondering why flat roofs are so ubiquitous for these structures. After all, wouldn’t a pitched roof be better at shedding water and adding value to your property?

While pitched roofs have their benefits for residential homes, there are several compelling reasons why flat roofs make the most sense for commercial buildings.

Key Takeaways

  • Flat roofs offer major upfront cost savings compared to pitched roofs.
  • They can be installed much faster due to simpler construction.
  • Equipment can be more easily stored and accessed on flat roofs.
  • Many flat roof materials provide improved energy efficiency.
  • Large commercial buildings require advanced drainage that flat roofs can provide.
  • Flat roofs seamlessly fit with modern commercial construction materials like steel and concrete.
  • With proper maintenance, flat roofs are durable and provide decades of service.

Why Do So Many Commercial Buildings Have Flat Roofs?

Flat roofs are ubiquitous on commercial buildings, but why? This in-depth guide explores the many benefits of flat roofs that make them an ideal choice for commercial structures, including cost savings, fast installation, equipment storage, energy efficiency, and more.

It also covers the most common types of flat roofing systems, as well as maintenance tips and signs that your commercial flat roof needs replacement.

Whether you’re constructing a new building or replacing a roof, this article helps explain the advantages of flat roofs for commercial applications.

Cost Savings

One of the biggest factors is cost. Installing a flat roof is significantly cheaper than a pitched roof for a commercial building.

Less material is needed to cover the roof area, and the construction is simpler without complex angles and framing. This translates into major savings on the initial build cost.

For a large commercial structure, this difference in price can be tens of thousands of dollars. That’s money that could be better spent on your actual business operations.

Quick and Easy Installation

Related to cost, flat roofs are also much faster to install. The simpler structure and smaller amount of materials means less time constructing the roof. For a business owner, minimizing the time your operations are shut down for construction is crucial.

A flat roof can be installed in a fraction of the time compared to a pitched roof. That’s less business downtime and quicker time to open your doors.

Equipment Storage & Access

Flat roofs provide ample space for storing mechanical equipment like HVAC systems. This equipment can be installed right on top of the roof rather than taking up valuable interior space needed for your business activities.

Equipment placed on a flat roof is also easily accessible for any required maintenance. Technicians can access it safely without interfering with your normal operations. Pitched roofs make equipment storage and access much more difficult.

Energy Efficiency

Energy Efficiency

Many modern flat roofing materials are designed to be highly reflective. This helps reduce cooling costs in the summer by keeping the interior building temperature lower.

Flat roofs are also ideal for mounting solar panels in an optimal angle for energy production. Going with a “cool” or green roof is a great way to improve your building’s energy efficiency.

Drainage & Ponding Prevention

Larger commercial structures require more advanced drainage systems to handle the huge volume of rainwater runoff. Flat roofs allow for internal drains and pipes that can capture all this water and prevent ponding issues.

Gutters are generally too small for commercial buildings. But flat roofs have many more effective drainage options available.

Seamless Fit with Modern Materials

Most contemporary commercial buildings utilize concrete and steel construction. The composition of these materials makes it difficult to install wood framing and gutters needed for pitched roofs.

Flat roofing membranes and systems integrate seamlessly with the steel and concrete used in modern commercial builds.

Added Space

A flat roof optimizes the total footprint of your building. More space can be utilized compared to a pitched roof on the same size structure.

Some creative businesses even add patios, gardens, and other outdoor spaces on their flat roofs. The flat surface provides added real estate.

Easy Access to Maintenance & Repairs

Walking on a steep-pitched roof is dangerous and requires special equipment. A flat roof can be safely accessed with basic precautions for regular maintenance like clearing debris.

It’s also much easier to spot potential leaks, cracks, and damage on a flat surface. Any roof repairs can be made more safely and quickly.

Long Lifespan with Proper Care

With routine maintenance and care, commercial flat roofs can easily last for decades. The upfront cost savings mean you aren’t sacrificing longevity down the road by choosing a flat roof.

Make sure roof drains are cleared, clear debris, and address any minor repairs, and a flat roof will provide many years of leak-free performance.

Common Flat Roofing Systems

Now that you know the benefits, here are some of the most popular commercial flat roofing systems:

  • PVC – Durable, weather-resistant, and long-lasting (20+ years). More costly upfront but very cost-effective long-term.
  • TPO – Affordable, easy to install, and energy efficient due to light color.
  • EPDM – Synthetic rubber roofing that’s durable and reliable. The most common flat roof type.
  • Modified Bitumen – Asphalt/plastic or rubber composite that is very waterproof.
  • SPF – Sprayed-on polyurethane foam, seamless and custom-fit.
  • Built-Up – Asphalt, felt, and gravel/stone topping. A time-tested reliable system.


Why are flat roofs used when pitched roofs shed water better?

Flat roofs allow for built-in drainage systems that handle the much larger water volume coming off enormous commercial structures. Proper drainage prevents ponding issues.

Don’t flat roofs leak more than pitched roofs?

Not inherently. When properly installed and maintained, flat roofs do not leak any more than pitched roofs. Regular maintenance helps prevent leaks.

What are signs my commercial flat roof needs replacement?

Consistent leaking, warped areas that don’t drain, cracking or blistering membrane materials, and excess ponding after rain indicate it’s time for a new flat roof.

How often should flat roofs be inspected?

Commercial flat roofs should be inspected at least twice per year, in spring and fall. This helps spot potential issues before major repairs are needed.

What’s the best flat roof for longevity and durability?

PVC is considered the most durable flat roof material, with expected lifespans over 20 years. EPDM and modified bitumen also provide long service lives. Regular maintenance helps maximize lifespan.


There are clearly many compelling reasons why flat roofs prevail on commercial buildings – from cost to structural benefits.

By understanding the advantages, you can determine if a flat roof makes sense for your upcoming commercial project. With routine care and maintenance, a flat roof will provide many years of reliable performance.

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