Intensive vs. extensive green roofs

Green roofs are a sustainable solution to combat urban heat islands, manage stormwater and improve air quality. These living roofs, which are partially or completely covered with vegetation, offer numerous ecological and economic benefits. However, their effectiveness and longevity depend on the type of green roof and the underlying roofing membrane.

There are two main types of green roofs: intensive and extensive.

Intensive green roofs, also referred to as ‘rooftop gardens’, are designed to support a diverse array of vegetation, including trees, shrubs, flowers, and even small water features. The depth of the growing medium can range from 15 to over 60 cm, providing ample space for root growth and plant diversity. This makes the roofing system heavier due to deeper soil and larger plants, and requires a robust structural support. Maintenance is relatively high, requiring regular watering, fertilizing, pruning and weeding.

Intensive green roofs are ideal for buildings that can support their weight and are often used in commercial properties, residential buildings and public spaces where aesthetic and recreational value are prioritized. They are typically accessible.

In contrast, extensive green roofs are designed to be lightweight and low-maintenance. They feature a shallow growing medium, typically 5 to 10 cm deep, and are planted with hardy, drought-resistant vegetation such as sedums, grasses and mosses. These roofs are primarily functional, focusing on their environmental benefits. Because they are much lighter than intensive roofs, they place less stress on the building structure. Maintenance is also minimal.

Extensive green roofs are suitable for a wide range of buildings, especially where budget constraints and structural limitations are important considerations. They are typically inaccessible to the public.

The choice of green roof will depend on factors such as roof structure and slope, desired vegetation, stormwater management requirements and annual local rainfall. For example, not all buildings will be suitable for intensive green roofs due to certain weight limits and size constraints. Therefore, they are typically planned by an architect during the design phase, before the building is actually constructed. Extensive green roofs, on the other hand, can easily be added onto an existing building.

The success of both intensive and extensive green roofs relies heavily on the composition and quality of the underlying roofing system. Layers of a green roof may include, on top of the structural roof deck: a vapor control layer, thermal insulation, roofing membrane, root resistant layer (mostly for intensive green roofs), drainage layer, filter membrane, growing medium (soil) and finally the vegetation itself.

Single-ply roofing membranes such as Elevate RubberGard EPDM and UltraPly TPO provide a lightweight waterproofing solution with outstanding durability. They are resilient enough to withstand the weight and stress of a green roof, require minimal maintenance and are easy to repair, ensuring that any issues can be quickly addressed without much disruption. RubberGard EPDM and UltraPly TPO are also root-resistant, preventing plant roots from penetrating the membrane and causing leaks. 

By choosing the right roofing system, building owners can maximize the benefits of their green roofs, contributing to a more sustainable urban environment while protecting their investment. As green roof technology continues to evolve, the synergy between advanced roofing membranes and innovative green roof designs will play a pivotal role in shaping the cities of the future.

Discover why Elevate EPDM and TPO roofing membranes are the perfect match for green roofs.