top principles in the design of a roof garden terrace

10 principles in the design of a roof garden terrace

Most of us respond unconsciously to the familiar layout and order of the gardens around us. Park scenery, our own back yards, the trees in our streets, all conjure a feeling we relate to the natural landscape that we know. These days, some of us have been gardening for a while on rooftops where the challenges are entirely different to those lower down. Roofs are flat and are usually set within an urban environment. They do not undulate or have much open ground and are inaccessible to most wildlife - a pretty static situation. Positively, in the urban setting, the design of a roof garden will strive to relate not only to the interior of the residence but also to the landscape beyond. However, many roof gardens are situated in difficult to reach spaces and require an understanding of the basic limitations in order to enhance usage and maximise the outdoor experience.

1. Access 2. Wind 3. Planters 4. Plants 5. Drainage 6. Irrigation 7. Weight 8. Furniture 9. The sky 10. Landmarks.

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  1. ACCESS.

Always consider access. It may not be possible to get long items into the site such as wood and tall trees. The lift should always be checked for size and all openings en route to the terrace measured for width and height. An external furniture lift is a good solution in tight London turnings though parking bay suspension may be required from the local council.

roof garden access

Southwark, SE London

  2. WIND.

Many roof terraces will be exposed to high winds. Plants should be selected for their tolerance of wind – small leaves tend to cope better with wind and grey leaves tend to cope better with hot sun.

roof garden wind

St George Wharf roof garden


Larger planters are preferable on roof terraces as they are well balanced and the compost tends to retain moisture for longer. Where the look might call for taller or narrower planters it is advisable to use some kind of an anti-topple device at the back of the planter and secure to it to a wall, handrail, etc. I find that this kind of architectural design is one of the best ways to personalise a contemporary urban terrace, particularly in London, where the ever-changing skyline provides new inspiration and opportunities to link the space further out.

roof garden planters

Thames Barrier roof garden   Planters relate to the shape of the barrier below

Hundreds of planters, over 10 years of design - explore the
shapes, colours and prototypes

  4. PLANTS.

Roof terraces will generally accommodate better those Mediterranean species that can endure wind, sun and drought. Garden favourites such as maples, bamboo and ferns are tempting but should be avoided in most exposed situations as their performance will be hindered. Pine, Olive, Birch and Ginkgo are good selections, not only for their added resilience to pollution but their architectural qualities in enhancing a contemporary terrace. With the abundance of specimen nurseries around London and the use of a furniture lift, immediate scale can be added to a terrace.

roof garden plants

Grosvenor Waterside roof garden  pine tree


Drainage for terrace planters and containers tends to get overlooked and this means that limescale from the water gathers on surfaces tarnishing their appearance. It is far more preferable to have drainage outlets at the bottom of the rear elevation of the planter rather than the base. This way water excess can be diverted elsewhere. Light weight material such as hydroleca is ideal to use at the bottom of the planters.

roof garden drainage

Canary Wharf roof terrace


Automatic irrigation not only eradicates the need for manual watering and saves a great deal of water but is paramount in sustaining growth on roof terraces. The right programming for the different seasons promotes good performance. In this contemporary building, the maple is sheltered within an overhang so irrigation is crucial is providing moisture all year round.

roof garden irrigation

Timer is set onto a tap extension

  7. WEIGHT.

Most new build roof terraces across London benefit from a steel and concrete fabric allowing a great deal of weight to be loaded. In older buildings and conversions it is advisable to consult a structural engineer to ascertain how much can be loaded and how it should be distributed. Most roof terraces would have the weight loaded along the edges, but where heavy loads such as bodies of water (pools, spas, etc) are to be incorporated this should be considered in the design.

roof garden weight

Milan roof garden


On windy roof terraces the right furniture must be considered. Too light and it will levitate into the sky… Where there is no eye contact directly from the property into the roof terrace, it is perhaps better to have stackable chairs that can be tied securely in a corner. In this central London terrace the fierce westerly wind along the river is tackled by using a heavy solid wood and steel furniture set.

roof garden furniture

St george Wharf roof gardens

Exquisite furniture sets to ponder on

  9. THE SKY.

The sky is a big feature in many roof terraces. Certain features will look great in sharp relief against the skyline. Colours should be chosen carefully to blend harmoniously with the sky – not only for when it is blue but also for the many days that it is grey. In London, where most of the backdrop is solid architecture, sculptural trees compliment geometrical forms effectively.

roof garden sky

Covent garden roof terrace   Cordyline palms against the evening sky


Allowing access to enjoy a great landmark in the view is what makes roof terraces such great places in the urban environment, particularly in a city such as London. Framing the landscape with appropriate scale and shape; the use of sculpture and lighting; leading the eye across by creating an interesting vista are all important elements that can help enhance the drama of a contemporary urban roof terrace.

roof garden landmarks

St. Paul's roof garden   Ginkgo tree framing St. Paul's Cathedral

See the most prominent London landmarks as seen
from our roof terraces

One of the most thrilling aspects of a London roof garden is how to create viewing points to the landscape beyond. An effective design for a roof garden will create a new topography from the flat surface. Layered foliage groupings, split level decks, eye level focal points, positioning of trees, sculpture and seating are all paramount in manipulating the spectator’s eye along the sequence.

amir   Written, photographed (unless indicated) and posted by Amir Schlezinger.

roof garden view

King's Cross roof garden   

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