Extensive Green Roofs or Ecoroofs
Typically 3-6 inches deep with a saturated weight of 15-30 lb/sq.ft. They are ideal for the growth of drought-tolerant plants, particular succulents like Sedum. They don’t need irrigation and only little maintenance. Due to the low maintenance, they are the roof of choice for building owners looking to reduce costs and improve the environment.
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Semi-intensive Green Roofs
Usually 6-12 inches deep with a saturated weight of 30-50 lb/sq.ft. Whether irrigation is necessary ore not depends on the regional climate and on the kind of plants that are used. Shrubs, perennials, herbs and grasses can be used on semi-intensive roofs. Maintenance is still quite labor intensive because the design of most semi-intensive greenroofs is still garden-like.
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Intensive Green Roofs 
For intensive greenroofs, the growing media is fairly deep – usually more than one 1 foot – and supports shrub and tree growth. A roof top garden or a patio is an example of an intensive roof. The saturated weight is 70 lb/sq.ft or more and irrigation is necessary in most cases. They also require a lot of maintenance, like any other well-kept garden does.
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