The Basics of Flat Roof Systems

Workers installing a flat roof.

What is the best material for a flat roof?

Large spanning commercial structures commonly have a flat roof, or one that appears to be flat. But are flat roofs really flat? Not exactly! What we see as a flat roof actually has some slope to it, a must for drainage. The normal slope is one-quarter to one-half inch per foot. This is a very low slope, and it takes ice, rain, and snow a long time to drain, which means the flat roof membrane must be watertight. 

Not all flat roofs are the same though, so what are the different types of flat roofs? Before you have a commercial roof installed or replaced, you should have a basic understanding of the different flat roof types available: 

  • BUILT-UP ROOF : The oldest commercial roof in the industry, but still a popular choice. This flat roof system is a continuous membrane that is semi-flexible and layered on the flat roof in piles that are alternated with an aggregate. A more common name is “tar and gravel”. This is an easy flat roof for repairs but offers no energy efficiency like many newer roof materials. 
  • PVC / TPO FLAT ROOF: These are single-ply flat roof membranes that offer reflectiveness with their white coating. Both are ideal for a restaurant’s roofing, with a high resistance to chemicals, fats, and oils. They are installed with heat welded seams to make waterproof, a labor intensive install job. 
  • EPDM FLAT ROOF: This impact resistant flat roof material can take whatever the weather is dishing out. It’s a rubber-like material made with tried and true technology used for over 40 years. The basic black color is not reflective, but a white coating will give you the reflectiveness you need. 
  • MODIFIED BITUMEN FLAT ROOF: Another type of rubber roofing that is installed in layers of a petroleum-based substance to achieve a rubber look and feel. It holds up to foot traffic better than many other roofing materials. It is a durable product but not reflective, therefore not an energy efficient flat roof material. 
  • GARDEN FLAT ROOF: A flat roof with a garden can be complex, requiring engineering inspections and routine maintenance. It may not be the best for a business but is ideal for residential structures with flat roofs, like apartment buildings. A flat roof with a deck ideal with a community garden. 

Is a flat roof a good idea?

For a commercial structure, yes, a flat roof is typically a better choice for several reasons: 

  • HVAC Equipment – Installed on a flat roof, equipment has more room, and by being able to place equipment on the roof the chances of copper theft are minimized. 
  • Better Drainage – The bigger a roof is on any type of structure, the more rain it will collect. This means typical gutter systems can’t handle a high volume of rainwater. A flat roof has a specific drainage system ideal for this roofing that can handle large amounts of water. 

Other benefits of a flat roof are aesthetics, as it blends in with other commercial structures around you, allowing owners to focus on the exterior siding. A flat roof offers a business additional space if desired for things like a garden, easing the urban island heat effect. Additionally, a flat roof will have a longer lifespan when it is installed correctly and maintained as recommended. 

What are two advantages of having a flat roof?

The biggest advantage of a flat roof for a commercial structure is the affordability in installation, maintenance, and upkeep. There is less labor needed when installing a flat roof, it can be installed faster, and once it is installed maintenance is minimal, another labor-saver. Another key advantage of a flat roof is having space for installing an HVAC system or going with a flat roof solar racking.

Is a flat roof cheaper than a pitched roof?

For a commercial structure, absolutely yes! A commercial flat roof is significantly less expensive because there is less material for the expansive area they must cover. This all equates to fewer materials and less labor, which makes the cost even less than with a pitched roof.

How long do flat roofs last?

A commercial flat roof that has been professionally installed and properly maintained can give you a 20 to 25 years lifespan. On the other end of the spectrum, a commercial flat roof that isn’t installed correctly and in cases where maintenance is not kept up, you may only get 10 years before a recoating is needed. There are commercial flat roofs that have lasted as long as 50 years as well. 

View of a flat roof from above.

In Conclusion 

A commercial structure with a flat roof or balcony should be installed by a professional contractor with experience in that particular area of construction. With a commercial structure, you shouldn’t rely on employees with weekends free and side business simply because of the liabilities that can leave a business open to experience. To learn more about flat roofing systems in Kingwood, TX, call Mdw Roofing and Remodeling LLC today at (832) 766-9994.