Vegetative Roofs: A Look at the Disadvantages

By Eric J. Seaverson, P.E.  
OTHER PARTS OF THIS ARTICLEPt. 1: What are the Benefits of Vegetative Roofs?Pt. 2: This PagePt. 3: Specification Tips for Extensive and Intensive Vegetative RoofsPt. 4: Vegetative Roofs: Secondary Components Include Root Barriers and Vapor RetardersPt. 5: Vegetative Roofs: Ensuring Proper Design and InstallationPt. 6: Vegetative Roofs: Pay Attention to Base Flashing and Penetrations

Although vegetative roofs offer many benefits, managers also must consider the disadvantages of such systems:

Maintenance. While conventional roofing membranes require periodic maintenance to repair membrane degradation, vegetative roofing requires periodic landscaping maintenance to remove unwanted weeds and other plants so they do not overtake and detract from the plantings. Managers also must determine whether grounds workers or roofing technicians are responsible for maintaining system components.

Increased costs. Depending on the selected planting method — modular vs. built-in-place — or overburden system, a vegetative roof can cost up to twice as much as a conventional system.

Membrane access. If leaks occur, the planting or overburden systems cover the membrane system. Inspectors must remove this top layer to find and repair the cause of leaks. As with any system, this process is challenging because the interior leak might not align with the membrane breach.

Unwanted wildlife and insects. The planting systems provide suitable habitat for birds, insects, and other wildlife, which managers might not want. Managers might have to specify additional protection to prevent unwanted wildlife and insects from inhabiting the system.

Contact FacilitiesNet Editorial Staff »

  posted on 12/30/2009   Article Use Policy

Related Topics: