How to create your own living roof   

Living Roofs Can Turn An Unused Space Into An Attractive Feature And An Important Mini Eco System 

The living roof, or green roof, as it is sometimes known, is fast becoming popular as a way to minimise the impact a new building has on its environment. From office blocks to garden sheds, from downtown New York to backyards in rural England, living roofs can offer an attractive way to use make use of available space while retaining the valuable and fragile ecosystems that would otherwise be destroyed by development 

At the smaller end of the scale, gardeners with limited space and an eye on the environment are using the living roof method on garden sheds and chicken coops. Homeowners expanding their properties are considering using living roofs on small extensions as a way to retain valuable garden space and to minimise the impact of their expansion on the environment. They have even been employed on a larger scale in high-rise developments in major cities such as New York. 

The living roof, or green roof is basically a roof space designed in such a way as to retain a growing medium which, when planted with suitable species of plants and grasses, produces a mini eco system on the roof of a building, albeit overhead, rather than underfoot. They can be used to turn an otherwise unusable space into a valuable habitat for wildlife and insects, which will enhance your surroundings and contribute to the long-term sustainability of the environment. With the right choice of plants, living roofs can be an attractive addition to any setting however small or large. If you can see a roof from your home or office, why not make it into a living roof? And transform an otherwise useless space into an urban oasis. 

Living roofs not only look attractive but can also have the effect of keeping a building cool in the winter and warmer in the summer as the layer of soil acts as a very effective insulation. They can also prolong the life of the roof structure itself by shielding it from direct exposure to the elements. In urban settings a living roof can also reduce the amount of rainwater running directly off buildings and into storm drains and thus reduce the load on municipal drainage systems, which in turn reduces the likelihood of floods. 

If you would like to try creating your own living roof, the simplest way to start is on a small project like a garden shed. It’s a cost effective way to try out the green roof concept and isn’t beyond the capabilities of most DIY enthusiast’s. It also adds an interesting focal point to any garden. 

Almost any roof can be utilised as a living roof although, the shallower the pitch, the easier it will be to create. A flat roof is obviously the most suitable but pitched roofs are not precluded from ‘going green’. With pitched roofs you will need to form the structure in such a way that the substrate will not slide off. This usually involves building up the sides to a suitable depth around the perimeter of the roof and if necessary, placing some extra timbers across the width of the roof to act as anchors for the soil and plants. The roof structure needs to be of adequate construction to support the weight of the living roof in a worst-case scenario so you need to consider the combined weight of the roof structure itself and the soil and the plants when fully grown. Add to this the weight of the water in the soil after a heavy fall of rain and the possibility of snow and you can see how it all adds up. If in doubt, consult a professional on the steps you will need to take to provide adequate support. 

If you are modifying an existing structure this will usually be no more than adding a few extra roof timbers in strategic points on the roof or adding an extra layer of decking. Better still, if you are building from scratch you can account for the extra weight at the design stage and upgrade the roof structure appropriately. 

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When your structure is in place you will need to add a waterproof membrane. On the simpler structures this can be a sheet of heavy gauge damp proof membrane of the type used in the construction of houses to protect against rising damp. This is inexpensive and easily available from any builder’s merchant.  

In order to retain enough moisture to support the plants, a moisture layer can be added. This can be made by adding a layer of old blankets or cardboard over the damp proof membrane. This is especially important in the case of a pitched roof as the soil may dry out very quickly as the pitch drains water away. 

When the structure is complete, you can add the growing medium or substrate. Soil or clay is generally too heavy to use on a living roof so a 50/50 mixture of compost and a synthetic material like vermiculite is used. Place the medium on the roof and rake into position. A depth of 6 inches is ideal for most roofs but it can be as little as 2 inches if you need to keep the load to a minimum. Remember though, shallower substrates will retain less water and you will have to choose your plants accordingly. Try to overfill with substrate and compact well as you go, as it will inevitably subside over time otherwise. 

Some of the most attractive living roofs are a simple mixture of native wild flowers and plants. The growing conditions in most green roof setting are ideal for a wildflower meadow and the flowers and seed heads are a valuable source of food for wild birds, while the growing stalks provide a haven for native insect species. Creating a mini eco system like this on your roof is a valuable addition to the local environment and provides a myriad of benefits to wildlife. Since the roof space is not subject to much disturbance it’s also a great way to provide for plant species that might be endangered in the wild. 

A wildflower meadow can be created simply by sowing a wildflower seed mixture and letting nature take its course. This is also a low maintenance option as the plants will require no further attention other than watering once they are established. 

For more specific undertakings a wide variety of plants can be used, especially rock dwelling plants and succulent types which retain moisture and generally thrive on a living roof.  

These include: 

• Sedums 
• Sempervivum 
• Arabis 
• Campanula
• Dianthus 
• Saxifraga 

These species can be purchased as plants rather than seeds and will quickly take hold and create a carpet of vegetation on the entire roof. Alternatively, some companies provide pre grown sedum mats, which can be rolled out over the entire roof area providing an instant roof garden. 

Whatever you choose to plant, be sure to plant in the spring or autumn when they have the best chance of  becoming properly established. 

Creating a living roof is a worthwhile project for anyone interested in actively reducing his or her impact on the environment and is a positive step towards creating an eco friendly lifestyle. It can be as simple as replacing the roof on the potting shed! So why not try it for yourself?

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