Why Do Commercial Buildings Have Flat Roofs?

why do commercial buildings have flat roofs

The roof of any building needs to keep the interior safe and dry. But Have you noticed that while most homes have sloped roofs, it’s more common for commercial buildings to have flat roofs? There are some differences between residential and commercial building design that result in commercial roofs being flat.

Are flat roofs really flat?

In fact, while commercial roofs may appear completely flat, they actually are designed with a very slight slope. That’s why you may hear commercial roofers using the term “low-slope roofing”. The slope may be as little as 2%, usually measured in inches-of-slope per-foot of length. That allows rain and snow to drain towards the building’s gutters or roof drains. No commercial or residential roof should allow water to pond in a low-spot for more than 48 hours after new rain, otherwise permanent roof damage and leaks can occur.

Why Do Commercial Buildings Have Flat Roofs?

Every building has unique needs, but here are the nine main reasons why most commercial roofs are flat:

  1. Simplicity. Flat roofs are simpler to design and install on large commercial buildings. With most residential structures being smaller than commercial, it’s easier to install sloped roofs on them. Complicated commercial structures function better with a simple flat roof.
  2. Utility. Many commercial properties aren’t designed for aesthetics like residences are. Therefore, commercial developers can save money by installing a flat roof rather than an eye-catching sloped roof.
  3. HVAC mechanical. Many commercial buildings are designed to have HVAC mechanical units placed on the roof. This saves valuable space around the building that can be used for parking, signage, or other purposes. Commercial HVAC roof-top-units (RTUs) are large and heavy and require a sturdy, flat surface for installation.
  4. Water drainage. Instead of gutters all the way around a sloped roof, commercial properties tend to have only a few high-capacity drains installed. Those drains may be near the center of the building, which can only be effective if the roof is flat.
  5. Maintenance. Commercial properties require a lot of upkeep to HVAC RTUs, signs, solar, electrical, and even the roofing system itself. Designing the roof to be flat allows multiple different crews to access the area and keep the property running smoothly.
  6. Reflectivity. Without the roof being visible from the ground, it’s common to install a reflective roof material like TPO membrane that reflects solar rays. Reflective roofs help reduce heat-island effect that is common with asphalt based, heat-absorbing roof materials. This can help keep energy usage at the property to a minimum and ensure the commercial building is as efficient as possible.
  7. Roof decks. Rooftops provide great views and allow commercial building owners to activate the rooftop into usable space. This is not an option for buildings with sloped roofs. Roof decks require special attention for protecting the roofing material, but can be major value drivers for commercial property owners.
  8. Green space. Another common use for commercial rooftops is green space installations, which also help reduce heat-island effect.
  9. Material durability. Product innovations have resulted in flat roofing materials that are rated to last multiple decades. This helps commercial building owners feel more confident in building their property with a flat roofing system. Many of the best commercial roofing materials, like TPO, EPDM, PVC, built-up asphalt, and modified bitumen will provide the building with protection for years or decades before needing to be replaced.

Sloped Commercial Roofs

Not all commercial roofs are flat. It’s common to see retail centers, small office buildings, and multi-family housing with sloped roofs. These are usually build using asphalt shingles, but may also be built using metal roofing for industrial properties, or slate/synthetic roofing for higher-end properties.

Denver Commercial Roof Maintenance

Whether your commercial roof is flat or sloped, it’s important to have an experienced team on board to help you maintain the roof. An annual commercial roof inspection and tune-up will keep your roof’s warranty in compliance, and satisfy your commercial property insurance requirements. The commercial roofing team at Sol Vista Roofing can assist in putting a plan together to maintain your property and ensure the roof lasts as long as possible.

Coating a Commercial Flat Roof

One of the benefits of a flat roofing system is the roof’s life can be extended by multiple decades with a professional roof coating. Roof coatings can be silicone, acrylic, or eco-plastic such as Castagra, and are applied in a liquid form and allowed to dry. When a flat roof gets near the end of it’s life, a professional coating is often the best option to get the most out of the existing roof and delay the need for a roof replacement.

Commercial Flat Roofing in Denver

If you need a commercial roof installed, replaced, repaired, or maintained in Denver, we encourage you to do your research and find an experienced contractor. The right commercial roofing contractor should work to extend the life of your roof as long as possible and only recommend replacing it when it’s absolutely necessary. When you’re ready to talk commercial roofing, contact Sol Vista Roofing to get started!