Just Why Do Commercial Buildings Have Flat Roofs?
If you’re considering a new roof, you might be wondering “Why do commercial buildings have flat roofs instead of sloped roofs?”
It’s easy to see that the majority of commercial properties have flat roofs, whereas residential buildings are pitched. But just why do business owners prefer flat roofing systems?
Flat Roof vs. Pitched Roof
Flat roofs are also known as “low-slope roofs” because they’re not completely flat. The fact is that all roofs need to have at least a small amount of slope, or pitch, to allow water to run off.
Pitched roofs are more common on residential homes, and typically homeowners lean toward one of two popular choices: asphalt shingles or metal roofing. This type of roof design allows water to run down the slope of the roof, into gutters, and then through downspouts away from the building.
Flat roofs have drainage systems that are often more complex simply due to the amount of water that must be directed off of the roof. Upon installation, roofers use a combination of drains and scuppers.
Drains direct water off of the roof toward downspouts, while scuppers allow water to drain directly off the side of the building. Drain maintenance is key because if drains become blocked by leaves or other debris, water can pool on the roof and eventually cause damage to the commercial roof. Standing water also attracts birds and insects, while promoting plant or algae growth.
Flat Roof Drain Systems
Flat roof drainage systems typically employ one of two systems: gravity systems or siphonic systems.
Gravity systems, like the name suggests, rely on gravity to funnel water through pipes toward downspouts for commercial buildings. However, when a building is the size of an industrial plant or mall, the sheer weight of water on the roof of these buildings can be dangerous. That’s why siphonic systems can be a better choice.
Siphonic systems employ a baffle that prevents air from entering the system, meaning that the pipes have a lower atmospheric pressure than the outside. When water enters the drain, it flows faster than it would by gravity alone. In fact, siphonic systems can drain water up to one hundred times faster than a gravity system!
Why Are Flat Roofs Common on Commercial Buildings?
More Usable Space
One of the reasons flat roofs are popular on industrial and office buildings is the amount of usable space they provide. Flat roofs can span larger areas than pitched roofs, which require additional structure. Installing frames large enough to handle a pitched roof on a large commercial building would be a waste of money and impractical.
Cost-Efficiency
Cost is a serious consideration for any business. Despite their enormous size, flat roofs are usually quite straightforward and easy to install. This keeps construction expenses to a minimum, and that savings can be invested back into the business.
Durability
Flat roofs are very durable, and when installed properly, can withstand adverse weather conditions like heavy snowfall and high winds. Their lifespan can last decades, even more than 70 years in the case of a metal roof. Overall, they require less maintenance than pitched roofing solutions.
However, roof repair may be required from time to time. Building owners should always turn to a professional commercial roofing company for regular maintenance and inspection to ensure the commercial roof reaches its maximum service life.
HVAC Systems & Other Equipment
Flat roofs are an ideal place for the large air conditioning units that are needed to cool large interior spaces. A pitched roof, by comparison, isn’t suited for roof-mounted HVAC units.
In most cases, service personnel can perform maintenance and repair to roof-mounted HVAC systems without disturbing customers or employees. This type of HVAC equipment also frees up valuable space inside/around the building, either for additional equipment or retail space.
Flat roofs also allow for easy installation of solar panels. This “green roof” can be especially helpful if you operate in climates where temperatures fluctuate dramatically throughout the year!
Common Flat Roofing Types
Flat roofs are usually constructed from one of several materials like thermoplastic polyolefin (TPO) or modified bitumen. A roofing contractor will be able to assess your building and determine the best, most cost-effective material for your roof.
Metal Roofs
Metal roofs are popular in both residential and commercial use due to their incredible durability and long lifespan. They also provide great energy efficiency, especially with the right roof coating. A metal roof with a white coating could qualify you for energy-saving tax breaks.
Single-Layer Membranes
Single-ply roofing options are manufactured roof membranes, such as TPO, PVC or EPDM roofing. These flat roofing materials are roofing technologies developed over the last few decades that can handle temperature changes well due to their elasticity.
Built-up Roof
A built-up roof is the oldest type of flat roofing. Also commonly known as BUR, a built-up roof is made of roofing felt that is applied in multiple layers held together with tar. The layers are applied until the desired thickness is achieved, and then a layer of fine gravel is placed on top to protect the BUR from UV rays and aid in water evaporation.
Modified Bitumen Roofing
Modified bitumen is a modernized version of the old-fashioned BUR system. This type of roof is made of asphalt and synthetic rubber or plastic, which is then combined with reinforcing fiberglass to create a structure that is both flexible and waterproof.
Flat Roofs: The Best Roofing Solution for Commercial Properties
So why do commercial buildings have flat roofs?
Commercial properties need more space than a pitched roof can provide, flat roofs need fewer repairs and less maintenance, and they allow for the installation of heavy-duty equipment like HVAC machines or even solar panels.
When it comes to flat roofing needs, however, regular maintenance is still important to ensure that your system lasts as long as possible. Just because flat roofs are more durable than pitched roofs doesn’t mean you should skip out on all roofing services. To get the largest ROI from your roof, it’s important to catch issues early and stay aware of your system’s health.
