General characteristics of extensive and intensive green roofs

General characteristics of extensive and intensive green roofs (adapted from Green Roofs for Healthy Cities and the Cardinal Group, 2006).
Link to this table.

Characteristic	Extensive	Semi-intensive	Intensive
Growing medium depth	6 inches or less	Portions of the green roof above and below 6 inches, with a minimum of 25% of green roof area above or below 6 inches	More than 6 inches
Accessibility	Often inaccessible	May be partially accessible	Usually accessible
Fully saturated weight	Low: 10 to 35 lb/ft2 (48.8 to 170.9 kg/m2)	Varies: 35 to 50 lb/ft2 (170.9 to 244.1 kg/m2)	High: 35 to 300 lb/ft2 (170.9 to 1464.7 kg/m2)
Plant diversity	Lower	Greater	Greatest
Cost	Low	Varies	High
Maintenance	Varies, but generally lower than for intensive green roofs	Varies	Varies, but generally higher than for extensive green roofs
Stormwater management	Best cost-benefit balance	More growing medium and more vigorous plant growth provides marginally greater stormwater volume benefits	More growing medium and more vigorous plant growth provides marginally greater stormwater volume benefits