What is a Green Roof? 

Green roofs are becoming increasingly a prerequisite for planning approval, either through biodiversity action plans, flood risk reduction as part of sustainable drainage systems or legislation. 

Green roofs over many advantages for buidling developers, owners and their users. They create visual enhancement of the landscape and fully exploit the spatialopportunities for visual and recreational benefit with the possibility of planning gain and, in economic terms, green roofs can have long term financial benefits.

Green roofing systems are principally divided into the three main categories below.

What makes up a Green Roof?

Image: Sika-Trocal Green Roof System Build Up

Green Roofing System Types

Biodiverse Roof

Biodiverse roofs are created primarily for biodiversity purposes and can aim to recreate the habitat that was lost when the building was erected, or even enhance it. A ‘Green’ biodiverse roof would generally be broadcast with an appropriate seed mix to encourage specific plant types that will support certain bird and invertebrate species.Pre-grown mats containing mixes of drought tolerant wildflowers, grasses and herbs can also be installed to provide a more “instant” cover. Substrate depths may vary across the roof deck to promote a diversity of both shallow and deep rooted plants and ones which are more and less drought tolerant.

Extensive Green Roof

Extensive green roof systems generally provide a visual or biodiversity, designed to support plants with a lower maintenance requirement, e.g. sedums, grasses, mosses and some wildflower species. These planting types are able to survive on shallower substrate depths than other types of plants and require lower nutrient levels along with little or no irrigation requirement.

Intensive Green Roofs

Intensive green roofs (also known as Roof Gardens) are principally designed to create recreational and amenity spaces for people to enjoy. They are generally accessible and contain features similar to traditional gardens including lawns, trees, shrubs and hard landscaped areas.
Intensive green roof systems involve using greater substrate depths (usually above 200mm) and often create a larger weight loading on the roof. Intensive green roof systems require a higher level of maintenance, including regular irrigation.


Whichever type of green roof is specified Sika-Trocal recommend the use of a warm ballasted system, as this reduces the insulation thickness and effectively controls vapour diffusion. This is critical in a roofing system that will always contain moisture above the primary waterproofing membrane. 

As experts in roofing Sika-Trocal choose to work with experts in horticulture to provide self sustaining plant communities on the roof.