During the past several years, there has been increasing interest in the use of vegetative, green roof systems in the U.S. This follows years of use in some European countries. (For more information, see "Designing green roof systems: A growing interest," September 1994 issue, page 20.)
Although green roof systems are gaining popularity, there are few credible guidelines or requirements governing the design and application of green roof systems in the U.S.
The model building codes, International Building Code (IBC) and NFPA 5000: Building Construction and Safety Code, are largely silent on the topic of green roof systems. In fact, the only direct statement regarding green roof systems is in IBC's Chapter 16—Structural Design, where Section 1607.11.2.3—Landscaped Roofs indicates, "Where roofs are to be landscaped, the uniform design live load in the landscaped areas shall be 20 psf (0.958 kN/m²). The weight of the landscaping materials shall be considered as dead load and shall be computed on the basis of saturation of the soil."