The two main types of green roofs are extensive roofs, which have a thinner and lighter layer, and intensive roofs, which are thicker and heavier.
Extensive green roofs are suitable for roofs with relatively low bearing capacity because of their low weight, lower cost, and minimal maintenance requirements. They typically vary in depth between 2” to 6”, corresponding to a saturated weight of approximately 15-35 psf, and have a typical initial cost of approximately $8 to $20 per square foot.
Intensive green roofs offer a wider plant diversity and individuality, creating a higher potential to develop a more complex ecosystem. However, they are heavier, more costly, and require more maintenance. They typically range from 8” to 24” in depth, with a saturated weight of 60-200 psf, and have a typical initial cost of approximately $15 to $25 per square foot.
Semi-intensive green roofs fall between the extensive and intensive green roof. They have a slightly higher plant community, have a mid-range cost, and require periodic maintenance. They typically range from 5” to 10” in depth, corresponding to a saturated weight of 25-40 psf.
| TABLE I: Comparison of Extension and Intensive Green Roof Systems | |
| Extensive Green Roof | Intensive Green Roof |
|
|
