5 Great Flat Roof Material Options for Commercial Buildings

Flat Roof Commercial Roof in Los Angeles

At Central Roofing, we are asked constantly why commercial buildings have flat tops. The primary reason why is that the HVAC and ventilation units that rest on top of the building are away from foot traffic. You’ll see a flat roof on nearly every commercial building in Los Angeles, but they aren’t all the same. Addtionally, Commercial Roofs are flat roofs because they are much more cost-effective compared to pitched roofs. It’s easier to put a sloped roof on a small residential home, but to do the same on a very large commercial building would be impractical, dangerous, and difficult.  With a flat roof, you may think that there aren’t many roof options but that isn’t the case in fact YOU DO HAVE OPTIONS. In fact here are 5 Great Material Options For Flat Roofs.

All commercial roofing systems must create an impenetrable barrier between a building exterior and interior to prevent water damage. Six common systems used on commercial buildings include

• BUR or Built-Up Roof
• Modified Bitumen
• PVC or Polyvinyl Chloride
• Silicone
• TPO or Thermoplastic Polyolefin

Many factors determine which roofing material system is best for you. Some are

• Aesthetics
• Cost
• Durability
• Energy efficiency
• Lifespan

There’s no reason to be confused about which option works best. Let’s break this down further.

1. Built-Up or BUR System

A BUR system scores high in aesthetics because of its gravel top layer. It’s also durable and stands up to heavy foot traffic. Multiple layers make it energy efficient. It is inexpensive overall, but your roof might need additional reinforcement. Expect 15 to 30 years out of a BUR system. Here are some key things to know about Built-Up Systems.

On the plus side, Built-up roofs tend to provide excellent waterproofing and ultra-violet protection. Thanks to the aggregate top layer, they are also fire-resistant. Built-up roofing is generally low-maintenance and therefore costs little to maintain over its life.

On the downside, built-up roofing can be slow to install and, with the exception of cold bitumen processes, installation involves hazardous fumes. Overall, installation costs are relatively high, and some types of this roofing can be susceptible to wind and water damage.

2. Modified Bitumen

Modified bitumen is also a multi-layered system. A base layer is attached to your roof deck, and overlaps are applied with a durable permanent adhesive. A granule top boosts the final product’s aesthetic and reflects the sunlight well. Expect 10 to 20 years’ longevity. One of the great things about Modified Bitumen Roof Systems is their reflectivity of U.V rays. This can help to reduce energy costs, especially if lighter colors or more reflective top coatings are used. Also, due to the combination of fiberglass and/or polyester reinforcement layers, these roofs are tear-resistant and can handle foot traffic well. However, its lifespan is relatively low compared to other options and without a proper drainage system installed these commercial roofing systems tend to collect water which may cause the flat roof to wear down faster. 


3. PVC or Polyvinyl Chloride

You’ll pay more for PVC, but it’s worth it. This single-layer option uses a PVC membrane to resist water and sunlight. The material is rolled out in sheets so there are seams, but once sealed they’re stronger than the sheets. A PVC system can last up to 30 years.

Corrosion can be an issue in just about any setting, but more so in an industrial flat roof building where fumes, gases, or perhaps exhaust can put a heating and cooling system at risk of becoming damaged after some time. PVC is considered a good option for minimizing the risk and is often used to conform to mandated safety regulations. In properties, PVC ductwork can allow a cooling and heating system to run beneath the house without becoming corroded by moisture or even radon. Over time, metal ductwork with corrosion will need to be replaced. Ultimately, you could reduce costs with PVC ductwork.

However PVC’s can get quite expensive with bigger flat roof buildings, which may be a deal-breaker, and the gross weight of this type of commercial roofing system is quite considerable, which is something you’ll have to keep in mind. 

4. Silicone Roof Coating

If you prefer a seamless system, silicone may be the way to go. Silicone roof coatings are sprayed on your existing roof and cured. The seal is nearly impenetrable and energy-efficient, which makes it a little pricier. Silicone lasts up to 20 to 30 years. It’s also more environmentally friendly than the other options because it uses less material and has less hazardous waste to throw away. But Silicone Roofing Systems are very slippery when wet and have a foul odor during installation. 

5. TPO or Thermoplastic Polyolefin

TPO combines ethylene, propylene, rubber, and other fillers to give your building a durable and “green” roof system. We’re experienced in using this material, which has only been around since the 1990s. You can expect your TPO roof to last seven to 20 years.

In comparison to other thermoplastic membranes, TPO resists mold growth, dirt accumulation, tear impact, and punctures. It is made to be flexible and can allow for a flat roof building’s movement or settling. Reinforced TPO membranes can handle a building’s thermal expansion and contraction more effectively than other single-ply roofing products.

One of the biggest disadvantages of TPO is that it is a really young roofing technology. Manufacturers are still trying to figure out the best chemical formula that will make the product durable and long-lasting while maintaining a competitive price. Finding this right formula has been a challenge for many manufacturers and over the years there have been many documented instances of seam failures and material failures such as membrane curing and cracking. New and improved formulas continue to be tested, but it is not possible to tell at this point how long a new TPO roofing product will last. If you choose to purchase a TPO roofing membrane, it is advisable to get it from a manufacturer that has been around since the beginning of TPO production, as they will most likely have the most long-lasting formulation available on the market today.


As you can see you do have options even if you have a flat commercial roof. As with anything, there are pros and cons to each one and you’ll have to consider the maintenance, reliability, and nature-friendly properties. If you’re in the Los Angeles area and you’d like to get your commercial roof checked out. Be sure to check us out we’ve been in commercial roofing for 30 years and provide free estimates, Thanks for reading.

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