Green Roof Benefits and Costs: Is a Living Roof Worth It?

Green roofs — also called living roofs — cover the waterproofing membrane with a growing medium and vegetation layer. They're growing in popularity in the UK, driven by planning requirements, environmental credentials, and their undeniable visual appeal.

Types of Green Roof

Extensive green roofs use a thin growing medium (50–150mm) and low-maintenance, drought-tolerant plants like sedum. They're lightweight and relatively low-cost. Intensive green roofs use a deeper growing medium (150mm+) and can support a wider range of plants, including grass and small shrubs. They're heavier and more expensive but create genuinely usable garden space.

Environmental Benefits

• Attenuates stormwater runoff — reduces drainage system loading
• Improves urban biodiversity — valuable habitat for insects and birds
• Provides thermal insulation — reduces building energy consumption
• Reduces urban heat island effect
• Extends roofing membrane lifespan by protecting it from UV and temperature extremes

Cost Comparison

An extensive sedum green roof costs approximately £80–£130 per square metre installed, compared to £60–£90/m² for a standard EPDM or GRP roof. The premium is real but not enormous. For planning requirements in many urban areas, it may be non-negotiable.

Structural Considerations

Green roofs add significant weight — even an extensive sedum system can add 80–150kg/m² when saturated. The structure must be assessed by a structural engineer before specification. Most modern timber-framed extensions can accommodate an extensive green roof without modification.