A green roof is a living layer of vegetation and growing medium built over a waterproofed roof. It can help reduce heat gain, slow and absorb rainwater, support biodiversity and allow a building to sit more gently within its landscape. From shallow, low-maintenance ground cover to deeper planted roofs, the system can be adapted to different climates, roof forms and structural conditions.
What makes it special
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Living & evolving — Unlike a conventional roof finish, a green roof changes with the seasons, weather and natural succession. Its character develops over time rather than remaining completely fixed.
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Softens the building — Vegetation, stone and earth can help a building settle into its surroundings, visually connecting the roof with the landscape around it.
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Supports local ecology — Even a relatively shallow roof can provide habitat for insects, birds and microorganisms, particularly when planting is selected to suit the local environment.
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Manages rainwater — The growing medium and drainage layers can temporarily hold and slow rainfall, reducing the immediate volume of water reaching the ground during heavy rain.
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Improves thermal performance — The combination of vegetation, growing medium and retained moisture can reduce heat gain through the roof and moderate temperature fluctuations.
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Adaptable — Green roofs can be designed as simple, lightweight systems or as deeper planted landscapes, allowing the approach to respond to the climate, structure and character of each project.
Things to keep in mind
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Weight — The roof must be designed for the system when fully saturated after heavy rain, rather than its dry weight. Deeper planting means substantially greater loading and may require additional structural capacity.
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Water management — Reliable drainage is essential. The system should accommodate both everyday rainfall and extreme storms, with protected drains, overflow routes and clear paths for water to escape.
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Roof pitch — The steeper the roof, the more the growing medium and water want to move downhill. Pitched roofs require additional measures such as retaining battens, erosion-control layers or other forms of mechanical restraint.
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Waterproofing & roots — Waterproofing becomes difficult to access once the roof is planted. A continuous, root-resistant and well-tested waterproofing system, carefully detailed around edges, drains and penetrations, is therefore essential.
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Planting — Species should be selected for the local climate, exposure, rainfall and available substrate depth. Hardy, locally appropriate and low-growing plants generally make the most resilient and low-maintenance roofs.
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Maintenance — A green roof is low-maintenance rather than maintenance-free. Drains, edges and overflow points should remain accessible for occasional inspection, particularly in areas with heavy monsoons or where buildings are intermittently occupied.
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Natural colonisation — Some spontaneous growth can be welcomed as part of the roof’s character, but woody, invasive or deep-rooted species should be removed before they become a threat to the system.
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Designed to evolve — The aim is not to recreate the ground on top of the building, but to create a carefully contained living layer that can change, weather and develop its own character over time.
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