Is my Roof Suitable for a Sedum or Green Roof?

Written-by

Janet Richardson

Reviewed-by

Richard Burdett-Gardiner

Updated on

Sep 04, 2024

Is my Roof Suitable for a Sedum or Green Roof?

Green roofs in the UK can be both retro-fitted and installed on new buildings. Below is a quick checklist to use when considering property suitability for a green roof. 

Structural Assessment

• Load-Bearing Capacity: Can your roof support the additional weight of a green roof (typically 60-300 kg/m² for extensive, up to 1500 kg/m² for intensive)?
• Roof Slope: Is your roof slope between 1° and 30°? Flat roofs and gently sloping roofs are ideal.
• Building Height: Consider the height of your building as taller buildings may require additional wind protection.

Roof Condition

• Waterproofing: Is the existing roof membrane in good condition or does it need replacement?
• Drainage: Is there an adequate drainage system in place to handle excess water?
• Roof Access: Is there safe and easy access for installation and maintenance?

Environmental and Legal Considerations

• Local Climate: Is your local climate suitable for the types of vegetation you plan to use?
• Building Regulations: Have you checked with local authorities for any regulations or permits required for green roof installation?
• Sunlight Exposure: Does your roof receive sufficient sunlight for plant growth?

Budget and Maintenance

• Budget: Have you budgeted for both installation and ongoing maintenance costs?
• Maintenance Plan: Do you have a plan for regular maintenance, including irrigation, fertilization, and inspection?

Professional Advice

Consultation: Have you consulted with a green roof professional or structural engineer to evaluate your roof’s suitability? 

Further info

The angle or pitch of the roof is a factor to be taken into account when considering installing a green roof. It is most common for flat roofs to be ‘greened’ (especially using the thicker, intensive type), though it is possible to install a green roof on titled roofs. Steeply inclined green roofs sometimes use the same arrangements as green walls.

Given that the heavier intensive green roofs can be highly elaborate installations featuring gardens with gravel, paving slabs, safety barriers and garden furniture (to say nothing of irrigation and drainage systems), these often require significant structural improvement work (using steel and concrete structures) in order that the roof can take the weight of the installation. Moreover, that this type of green roof often also requires more maintenance, it is necessary that the roof be safe to walk on. It is for this reason that engaging a specialist engineer is absolutely vital when considering installing any kind of green roof (even the lighter, extensive variety).

The load-bearing ability of the roof is probably the single most important consideration here. Regardless of the size or type, all green roofs (and walls, for that matter) will need exposure to sunlight, water and nutrients in order to remain alive. If, therefore, the proposed site is significantly covered by the shadows of nearby buildings, the installation of a green roof may not be viable.

During the installation of the green roof it will be necessary for the installers to gain access to the roof. If access to the site is tricky, it could add significantly to the cost of the installation.

The potential effect on (or, indeed, benefits for) the local wildlife population is also something which must be taken into account when considering a green roof. Useful information on local wildlife populations and habitats for those thinking of installing a green roof can be found on the website of The British Wildlife Trusts: http://www.wildlifetrusts.org/.