The vivid hues of a living roof can add an inviting design flourish to your home, plus boost the house’s green credentials by forming an insulating layer that helps to reduce heat loss.
The term describes various systems, from simple setups with a hardy turf or sedum covering, to advanced roof garden schemes that are full of a selection of colourful shrubs.
This feature works particularly well in urban locations where it’s used as a tool to inject greenery into the setting.
Often specified as a covering for single-storey rear extensions, it provides a pleasant view for occupants looking down from the upper floors of the house, also adding an interesting visual detail from an exterior perspective.
In rural situations, green roofs can be used as a smart solution to help houses blend sensitively into the setting – particularly for Paragraph 55 dwellings constructed on green belt land.
This is why these living coverings are looked upon so well by planners, as it’s a straightforward way to show how the new building will be camouflaged within the plot, minimising its overall visual impact.
From a planning perspective, a green roof also establishes a biodiverse environment for bees, butterflies and insects, making up for the loss of habitat that may occur as a result of development.
Living roofs typically fall into one of two categories – intensive or extensive. The former is a flat roof garden planted with a deep layer of soil, while the latter comprises a thinner substrate and is more suitable as a finish for pitched structures. It’s worth noting that an extensive system will flourish best on a slope of 35° or less.
The planting scheme itself will depend largely on the orientation of your house, as certain plants thrive in sunny positions, while other varieties will bloom in shadier spots.
Many homeowners choose to personalise the setup by selecting seeds that correspond with the naturally-growing greenery in the local area. It’s important to consider maintenance at this stage of your project, as some plants require more upkeep than others.
Wildflowers will only need to be cut back once a year, for instance, while more advanced setups call for greater care, for which you may need direct access out onto the roof area.
Lizzie Webster, director & architect at Fraher Architects, provides her expert advice on how to
add a green roof into your project
In an extension scenario, it’s an element that’s best-appreciated from above. Often with a large ground floor rear addition you end up looking down onto a vast area of roof from the first or second storey windows. A living covering is then used as a screening device to reinstate landscaped space lost via development.
If this kind of aesthetic feature is used for the main house, it’s pretty much out of sight for occupants inside. However, it is possible to install rooflights in such a way that you create views up to the green roof.
If green roofs comprise a thick growing medium, they help to insulate a property, so we find that our clients are keen to incorporate them to reduce their utility bills and cut down their carbon footprint.
Of course, there’s the attractive visual aspect too. I’d say for most people that it’s usually aesthetics first and then sustainability – but with a green roof, these things come hand-in-hand.
This depends largely on how much substrate there is for the seedlings to grow into. Obviously some varieties need much more soil, whereas others – like sedum – can have a very shallow depth.
There’s also seasons to consider. If you have a wildflower roof, for instance, it’ll die back during winter. So, you might mix the planting by putting sedum in at the same time. That means when the summer flowers disappear, you’ll still have an orange and red carpet during the winter months.
We often use a mix of wildflower and sedum. At the moment, we’ve got a covering of the former on our roof that incorporates sunflowers and poppies.
But there are often blends that are appropriate to different locations. For example, there’s a combination of seeds you can get for planting green roofs for exposed coastal properties, as opposed to hillside, wet ones.
First of all, you’ll need to check the orientation of the surface to see whether this solution is suitable. The pitch of the structure shouldn’t be too steep, as flat or shallower roofs adapt better to a living system.
The main thing is to speak to a structural engineer to know if the roof can support the weight of the green layer, because once it’s absorbed rainwater it can get very heavy. You can retrofit a living covering, but in these cases you may need to use a much lighter weight green roof system – a sedum layer with a light soil is a good solution.
Check the waterproofing consistency of the structure, too. It’s vital to ensure you’ve got a robust surface in place first.