A DIY Guide to building your own eco enhancing Green Roof Garden

DIY Green Roofs provide many benefits when installed correctly - including water storage, decreasing flood risk, aesthetic impact and habitat creation. Whilst large-scale projects should be entrusted to specialist firms, smaller scale domestic projects, such as garage roofs and sheds, are relatively simple to install as long as they follow certain guidelines. This guide outlines some of the key guidelines for how to install a successful, lightweight DIY green roof.

Before Starting there are two important questions to ask yourself:

1. At what angle can I install a green roof? It is not recommended that you build a green roof on a slope of over 10° without specialist advice, when constructing a green roof on a slope of under 2° or over 10° there may be some extra design considerations to take into account.

2. Can the existing structure take the extra weight of the green roof?

Simple lightweight green roofs weigh between 60-150 kg/m2 (13.0-30.0 lb/sq.ft).  If you are unsure of the loading your roof can take, consult an architect or structural engineer before you do anything else. When calculating the weight that the green roof will impose on the roof, you must also take into account the weight of the green roof when saturated with rain or snow. If the existing roof is unable to take the extra weight, you may be able to reinforce it using wooden supports.

Getting started

Time needed

One day

You will need (2m x 1m (6ft 6 in x 3ft 3in) structure)

• 3 x 2m (6ft 6in) lengths of 20 x 2.5cm (8 x 1") timber
• 2 x 1m (3ft 3in) lengths of 20 x 2.5cm (8 x 1") timber
• 4 x 50cm (1ft 6in) lengths of 20 x 2.5cm (8 x 1") timber
• 10 x L-brackets
• Screws to attach the L-brackets
• Butyl lining
• 2m x 1m (6ft 6in x 3ft 3in) plywood board
• Electric screwdriver
• Tape measure

Build the frame

• Build the outer frame first then add a central strut for strength.
• Using the L-brackets, join together the outer sides of the green roof structure.
• Measure carefully and use the L-brackets to attach a 2m (6ft 6in) length of wood as a central support through the middle of the framework.
• Measure carefully again and use the L-brackets to attach the remaining lengths of wood widthways across the frame, creating a grid with six sections.

• Line the roof of your shed with a piece of plywood wrapped in waterproof butyl lining. This will protect the roof of the shed from any potential water damage.
• Lift the wooden frame into place.
• If your shed has a sloping roof, nail the frame to two strong vertical posts which have been cemented into the ground on the lower side of the shed roof.

Plant up

• Fill the frame with potting compost mixed with a good amount of perlite. This will give good drainage and stop the structure from becoming too heavy.
• There's a huge range of plants you can choose from that will grow on your green roof, but try to choose ones which will not grow too tall so that they will survive any potential wind or storm damage. Sedum matting is also a popular low-maintenance choice. A living carpet of sedum plants are grown on special matting which is simple to install. Remember to choose some evergreen species if you want year-round foliage on your roof.