Commercial Roofing: Understanding Flat Roofing Maintenance

Protecting your commercial property against inclement weather involves a number of critical factors. First and foremost, choosing the right roof for your property is key, but regular maintenance to ensure the structure and quality of that roof is also crucial. Indeed, a properly installed and effectively functioning roof has implications on property operations, improved tenant satisfaction, and even operational costs. As such, understanding commercial roofing and in particular flat roofing maintenance helps property owners and managers ensure that their building is in optimal condition.

As the most common type used in commercial properties, flat ones are incredibly common. Nevertheless, there are 5 basic types of flat systems, each with specific maintenance needs. In this article, we will discuss flat maintenance and definitions of built-up, modified bitumen, ballasted, single ply, and green systems.

Built-Up Roofing

Often abbreviated BUR, this type is your basic tar and gravel roof. First, felt that is treated with tar is rolled out onto your roof with plenty of overlap from one layer to the next. Then, hot tar is poured over the surface of the roof and between overlapping layers. BUR systems should last around 15 years, and when the system starts to fail new layers are added. Gravel is usually added as a topping material to enhance the durability of the roof.

Modified Bitumen Roofing

This type is similar to a BUR style but utilizes a pre-fabricated roll that features modified tar or asphalt with a rubber backing to improve performance. Typically, a BUR underlay is installed first and then the modified bitumen is applied using an adhesive or torch. These types are expected to last about 20 years.

Ballasted Roofing

This system comprises a membrane system that is simply laid on the roof deck and held in place with rocks or concrete pavers. The membrane and seams are sealed with an adhesive, and if properly maintained this type of roof can last upwards of 30 years.

Single Ply Roofing

Single ply sheets of a roofing membrane are installed and sealed at the joints so they are waterproof. These types are among the most expensive but can last over 50 years.

Green Roofing Systems

Increasingly popular in European and North American cities, green systems reduce power consumption and heat loss. These types are similar to ballasted types, but instead of using rocks or concrete pavers, soil and vegetation is applied. Green roofs may last around 20 years or more.


As you would expect with so many different types of flat roofs, maintenance can vary significantly. All flat roofing systems need to be regularly maintained and this maintenance program should include the removal of debris, damage inspection, and gutter and downspout cleaning. More importantly, damage inspections should include the roof and flashing, and repairs and upgrades should be made as recommended. Ultimately, you want to work with a qualified roofing professional to ensure your flat roof functions effectively.

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