7 August

Why Commercial Roofs Are Flat

Why Are Commercial Roofs Flat?

Have you ever wondered why commercial roofs are flat instead of arched or curved? In this article, we’ll teach you all about the purpose and benefits of flat roofs, as well as some interesting facts you might not have previously known. We have also included a list of the different types of flat roofing so you can gain a better sense of which type might be the best for your business.

Let’s begin with a brief history of flat roofing.

Where Did Flat Roofs Come From?

Flat roofing is an architectural practice that dates back as early as 7100 BCE, in the desert climates of North Africa and the Middle East. Later on in the 8th century, pueblo buildings were the first flat-roofed buildings constructed in North America. One of these buildings, the Taos Pueblo in New Mexico, still stands to this day and was built sometime after 1000 CE.

In the 19th century, built-up roofing (BUR) was developed in Europe, which served as the turning point for what we know today as commercial flat roofs. This roofing was first composed of tar and felt, then later replaced with asphalt and fiberglass. After further development of flat roofing in the 1960s, modified bitumen roofing was developed, then later thermoplastic membranes and rubber began their debut in roofing. We will discuss these different types in a later section.

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Uses of Flat Roofing Today

As you know, flat roofs are often used today for commercial buildings, such as hospitals, restaurants, malls, supermarkets, warehouses, offices, and much more. Additionally, while most houses still have arched and sloped roofs, there are many homes which feature flat rooftops for a modernist, mid-century appearance. 

Flat roofs are not recommended for homes located in climates of heavy rain or snowfall, however, as you must constantly remove snow, ice, or standing water from your roof to prevent it from caving in. Commercial buildings, on the other hand, have regular maintenance practices and preventative features in place that make snow and ice buildup less of an issue.

Why Flat Roofing is Mainly Used for Commercial Buildings

Generally speaking, most businesses focus more on practicality rather than aesthetics, and flat roofs serve purposes far greater than just protection from the elements. Commercial buildings require many mechanical systems in order to function, such as HVAC (heating, ventilation and air conditioning) systems, and flat roofs often serve as the storage space for these machines, along with other equipment. This space is also often used as a patio or green space, or a space for installing solar panels to save on electricity.

Many commercial buildings are also irregularly shaped, compared to residential buildings. Flat roofing can accommodate these irregularly shaped spaces in ways that arched roofs cannot. Additionally, considering how tall a lot of commercial buildings are, installing a roof with a slope can be very dangerous, for both the roof workers and people down below. Therefore, flat roofs are highly recommended, for both safety purposes and the benefits that they offer.

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Benefits and Downsides of Flat Roofing

Flat roofs require low maintenance when businesses choose high-quality materials, and they can last anywhere from 30 to over 50 years. While flat roofs can be expensive upon first installation, they are very cost-effective in the long-run due to how much longer they last than other types of roofs, and how easy and painless it is to install and repair them. Flat roofs also minimize use of the upper floors of commercial buildings, acting as a large storage space for materials.

Flat roofs are often composed of asphalt or rolled membranes, and these materials pose their own risks. Asphalt can deteriorate when used in the wrong environment, and it’s hazardous to work with and produces a bad smell. Rolled membranes leave seams after installation, which poses the risk of roof leaks, and the material can be prone to cracking. Also, with any flat roof, there is always the risk of pooling water.

It’s highly advised that business owners invest in higher quality materials for their roofing, to prevent leaking or other damage. Drainage reinforcements should also be installed to prevent standing water.

Five Types of Flat Roofing

  • Built-up roofing is the oldest type of flat roof, “built up” with layers of material. This is the cheapest option for businesses, but it can easily be damaged if not in the right environment.
  • Modified Bitumen roofing is more durable than a built-up roof but still needs to be maintained regularly.
  • PVC roofing has waterproof membranes and is both a cost-effective and ecologically friendly option, as its materials can be recycled. They are also resistant to chemical damage.
  • TPO roofing is similar to PVC roofing but is also both heat- and UV-resistant. However, it’s less resistant to chemical damage and often cracks.
  • Rubber roofing shares many of the same benefits as PVC and TPO roofing, but additionally comes in many different styles and colors. However, it’s not heat-resistant.

How Do Flat Roofs Drain Rainwater?

Without a proper drainage system, flat roofs cannot drain water naturally like a sloped roof can. Thankfully, there are three different types of effective draining techniques that are often used for commercial buildings:

  • Interior drains work similarly to shower and sink drains, and they are placed in the areas of the roof that get the most water, with pipes installed beneath. The pipes then empty the water into a gutter or spout outside.
  • Gutters are the most common drainage system for flat roofs, and the cheapest. They catch the water as it rolls down a slight slope and release it at a safe distance from the building.
  • Scuppers are considered the most effective out of all the drainage systems, and can be compared to the scuppers on a ship. Square-shaped openings are made on the sides of the roof which release the water, often into spouts positioned below.

PRO TIP: Learn more about Roof Storm Damage.

Conclusion on Why Commercial Roofs Are Flat

Business owners often choose flat roofs for their commercial buildings, not only because it’s the standard practice, but also because it can have many benefits. They are relatively easy to maintain, last for decades, and provide space for storage or recreational uses. Next time you pass by a business, you will now understand why commercial roofs are flat.

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