How thick is a green roof in mm?

Green roofs offer environmental and aesthetic benefits to homes and commercial property. They can provide insulation, absorb rainwater, and purify the air. When considering installing one, however, one question often posed is, “How thick is a green roof in mm?” Here, we will discuss all of the layers found on a green roof; their thicknesses, and what influences them!

Types of Green Roofs

1. Extensive Green Roofs

These are light in weight and require less maintenance, hence ideal for buildings with low load-carrying capacities.

• 80 to 150 mm thickness.
• Features:
  • Insufficient soil depth 
  • Support drought-resistant plants like sedums and grasses
  • Weigh less compared to others

2. Intensive Green Roofs

Also known as rooftop gardens. This is ideal for various plants, including shrubs and small trees.

• Thickness Range of 150 to 400 mm.
• Features:
  • Deep soil depth
  • Allows diverse vegetation
  • Requires regular maintenance and irrigation

3. Semi-Intensive Green Roofs

Semi-intensive green roofs combine features from both extensive and intensive types to produce optimal performance.

• Thickness Range of 100 to 250 mm.
• Features:
  • Moderate soil depth
  • Supports small plants, herbs, and flowers
  • Medium maintenance level

Key Layers of a Green Roof

Each layer in a green roof adds depth, contributing to its overall thickness. Let’s examine these layers:

1. Vegetation Layer

This layer covers the topmost portion and its depth will depend upon what kind of plants have been chosen for cultivation.

• Thickness: 20 to 150mm 
• Thin for grass or sedum, thick for shrubs and trees

2. Growing Medium (Soil)

A growing medium provides essential nutrition and stability to plants.

• Thickness: 50–300 mm
• Extensive roofs have shallow soil; intensive ones need deeper soil

3. Drainage Layer 

A drainage layer helps avoid flooding by discharging excess water quickly from accumulating on surfaces.

• Thickness: 20–50 mm

4. Filter Layer

Filter fabric separates soil and drainage layers by being very thin.

• Thickness: 1–3 mm

5. Waterproofing Layer

This protective barrier serves to seal off leaky areas in buildings; its thickness depends upon the material chosen.

• Thickness: 1-10 mm 

6. Root Barrier 

This barrier serves to keep roots from penetrating the structure below it and entering.

• Thickness: 1-5mm

Factors Impacting Green Roof Thickness

• Purpose of the Roof: Green roofs designed for aesthetic or biodiversity purposes will likely have thinner profiles, while those intended to serve agriculture or parks must have thicker layers.
• Building Load Capacity: Only older structures or those with low bearing capacities require very thin roof covers to support them.
• Climate Conditions: Locations that receive heavy rain require thicker soil and drainage.
• Type Of Plants: Plants occupying deeper soil layers will produce thicker foliage than their lesser-sized counterparts.

Benefits of Thick Green Roofs

Green roofs may be easier to install, yet heavier green roofs offer additional benefits that extend well beyond installation:

• Increased insulation benefits.
• Enhance stormwater retention capacity
• Increase biodiversity with various plant species

On the downside, however, they present greater maintenance and investment needs.

Related Read: How to calculate the roofing sheet?

The Bottom Line

How thick is a green roof in mm? – Although thickness can differ significantly depending on its purpose and location, on average green roof thickness ranges between 80 mm-400 mm. This will depend upon the size of the green layer installed as well as the species used. When planning for a green roof installation, consult an expert for guidance as you determine its appropriate thickness. A well-designed green roof can add beauty and contribute positively to our planet!In search of roof installation services around Edmonton? Our experts at A2ZRoofing ensure top-quality materials and professional service for lasting protection!