A green roof is a layer of vegetation planted over a waterproofing system installed on top of a flat or slightly sloped roof. It helps with insulation, stormwater management, and reducing heat in urban areas. The cost per square foot for installing a green roof can vary significantly depending on factors like the type of system (extensive or intensive), the depth of the soil, accessibility, and the layers involved such as waterproof membranes, drainage, and root barriers. On average, you might expect something in the range of $10 to $25 per square foot for a basic extensive green roof, which uses hardy plants like sedums and requires minimal maintenance. Intensive green roofs, with deeper soil and larger plants or even trees, can cost $25 per square foot or more, sometimes climbing well past $50 depending on complexity and design.
To get a rough idea if your roof is appropriate for a green roof installation, a simple DIY check involves inspecting the structural integrity and slope of your roof. You’ll want a solid, flat or gently sloped roof, ideally with a professional structural assessment since a green roof adds weight. Make sure there’s no existing water damage or leaks. If you do consider a professional, ask questions like: “What waterproofing and root barrier systems do you recommend, and can you explain their warranties?” and “How do you ensure proper drainage to avoid water buildup under the plants?” These questions help ensure your green roof is both durable and protected, keeping your investment safe for many years.