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Crafting Green Roofs


Semi-intensive Green Roof

A Semi-intensive Green Roof represents an enhanced natural form of vegetation, often self-sustaining and evolving. Certainly, it is still cost effective and a bio-diverse natural infrastructure to reduce stormwater run-off from buildings. Additionally, semi-intensive Green Roofs widely restore the environmental footprint of a structure, as it is proven to be rich in biodiversity and with high stormwater retention.

Of course, semi-intensive Green Roofs are a cross over between extensive and intensive Green Roofs.

For instance, semi-intensive Green Roofs partially placed on extensive Green Roofs increase the visual and ecologic effect. In contrast, semi-intensive areas on an intensive Green Roof will reduce costs and offer a transitional visual aspect.

Simplicity and Biodiversity

Semi-Intensive Green Roofs or simple intensive Green Roofs form a transitional Green Roof type from extensive to intensive greening. They are characterized by herbaceous plants, perennials, ground covers, grasses and even small shrubs. They require moderate maintenance and occasional irrigation depending on the location. To clarify, moderate maintenance means, it is slightly more than on divers extensive Green Roofs. However, the maintenance is equal to extensive Green Roof with a Sedums mono-culture.

A typical growing medium depth for a semi-intensive green roof is 6 to 10 inches. Further, this Green Roof type is able to retain more stormwater than extensive types and hosts a richer biodiversity. This Green Roof type also provides the potential for a formal roof garden effect. Of course, related to more target oriented maintenance.

Most of Green Roof Technology's extensive Green Roofs have "islands" of semi-intensive greenery because this substantially boosts biodiversity, resilience, and sustainability. Also on semi-intensive Green Roofs the vegetation is subject to natural reshuffling and natural succession, where plants species migrate or new plants species can settle.

Value added

Seamless transitions from extensive to semi-intensive Green Roofs offer the best value for the investments - visually and ecologically.

In general, semi-intensive Green Roofs have higher weights than extensive Green Roofs. And, keep in mind, weight is not a quality criteria for Green Roofs. In fact, plants do not care about the weight. After all, plants care about the porosity of materials, Air-to-Water Ratio, and nutrient exchange capacity to name a few. Since all Green Roofs are supposed to retain water (for the plants), the weight of a system mainly depends and varies on the amount of water within the system. This retained water is in higher in this type comparing to extensive Green Roofs.

Over all, the natural vegetation dynamic creates biodiversity and makes semi-intensive Green Roofs more resilient to Climate Change than extensive Green Roofs.

semi-intensive green roof

Comparison of Green Roof Types

Green Roof Type ➡️
Extensive Green Roof
intensive green roof
Stormwater Mitigation
Stromwater Mitigation,
Stormwater Mitigation,
Amenity Space
Shrubs, Trees
Overall Depth
4 to 7 inches
6 to 10 inches
200-750mm +
8 to 30 inches +
Weight Range
100-200 kg/m²
20-40 Lb/sf
120-300 kg/m²
25-60 Lb/sf
220-800 kg/m² +
45-160 Lb/sf +
Ecological Compensation
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Max. Rain Event
over 120mm
over 4.2"
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Irrigation System
not recommended
Solar Garden Roof
yes, optional with high ROI
requires custom tailoring
only as pergola
in amenity space
Blue Green Roof
standard with
Green Roof Technology
General Overview of Green Roof types ©️ Green Roof Technology

Advanced Green Roof Types
with Blue Roof Options

Traditional Green Roof Types with
Retention and Detention Options