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Up on the roof: How to design the perfect roof garden

By John Wyer of Bowles & Wyer. Imagine yourself up on the roof, surrounded by buildings, but somehow slightly removed from the hustle and bustle of life below: scanning the city from your own secret haven.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

I have been designing and building roof gardens for over 25 years and what I find most fascinating is the paradoxical sense of both inclusion yet separateness from the city. You are both part of, and apart from, the city. Of it, but above it. The sense of escapism is a critical part of the appeal of roof gardens, as well as the incredible vantage point they offer. From the roof, you can see a different side of the city, quite literally. And you can see the sky as well in a way that almost never happens at street level.

But creating a roof garden is complex. Aspects such as microclimate, planting and technical elements, such as weight-loading and drainage, all need to be carefully considered. Here I share some advice on the key design elements to create a successful roof garden.  

PLANTS & PLANTING

As a general rule, Mediterranean and coastal plants cope well on an exposed, sunny rooftop as well as plants normally found on rocky south-facing slopes.  When choosing plants bear in mind the environment that the plant originated from and the characteristics it has developed to help it survive in dry, hot and windy conditions. 

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

For instance, hairy leaved plants have the ability to block out too much sunlight and avoid drying wind, while plants with thick waxy leaves, such as euphorbias, tend to avoid water loss.  Other useful varieties are yuccas and pines which have narrow, pointy leaves which have a much smaller surface area from which to lose water.  Also, silver-leaved plants which reflect the sunlight to avoid drying out.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

Grasses tend to do well on roofs, but choose the varieties that flourish in cool seasons rather than warm ones. Other popular, and surprisingly hardy species, are agapanthus, olive and heather - all ideal for rooftop planting.  Finally, fragrant plants with essential oils, such as lavender and rosemary, are very drought tolerant, so a great choice for roof gardens. 

STRUCTURES & SHELTER

On a hot sunny day, an exposed rooftop can be almost unbearable without shade and, lacking the protection of surrounding buildings, rooftops are often windier, wetter or dryer than a domestic garden.  Ideal for providing shade, and with the added benefit of supporting plants, are pergolas and other vertical structures such as screens.  If you are incorporating these, remember permeable screens are much more effective at dissipating wind than solid screens, such as glass, which can create turbulence.  And while shaded areas are highly desirable for dining, don’t forget you might want a sunny space for lounging and sunbathing too.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

CONTAINERS & PLANTERS

Containers are an important part of the furniture of your outdoor room, so do give them some thought.  There is a wide variety of new materials on the market to choose from so don’t automatically go for terracotta pots.  Fibreglass or powder-coated steel planters often feature in our designs. We also like to use ceramic planters for feature trees to add impact. 

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

Other materials to consider are lead, zinc, bronze or ceramic, but whatever you choose, make sure containers are of sufficient size to stop them blowing over.  If you are grappling with a tight or awkward space and want to make the best use of it, or if you want to create 'zones' within the plot,  you could try bespoke planters.  One final tip for placement - to make the most of views from important windows try siting containers, specimen plants and even sculpture on the same axis.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

FURNITURE & SEATING 

As a general rule, try and avoid large or bulky furniture as it can dominate the space and feel somewhat overwhelming on a roof.  We often create built-in seating systems for our clients.  This allows us to make the seating area a central design feature and to position it to make the most of any views. You could also try combining planting with seating.  We often use tall plants in raised beds behind the seating to create a calming atmosphere and also to provide privacy from neighbouring properties.  Whichever style of furniture you choose, make sure it is strong and stable enough not to blow away. 

PHOTO CREDIT - Allan Pollok-Morris

PHOTO CREDIT - Allan Pollok-Morris

HEATERS & FIREPITS

Firepit and heaters are particularly magical on a roof, creating a natural gathering place on cooler evenings and allowing use of the garden well into the Autumn. They also add a wonderful focal point to a plot.  We use firepits and heaters fuelled by gel or gas for roof gardens.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

LIGHTING

As night falls, use lighting to create dancing patterns of light against the city skyline. Lighting is perfect for highlighting architectural specimen trees and geometric planters.  It can also add depth, drama and a terrific atmosphere to the space. Like heaters and firepits, lighting will naturally extend the length of time you can enjoy the garden throughout the year.

How to Design the Perfect Roof Garden by John Wyer at Bowles & Wyer

IRRIGATION & DRAINAGE

Plants can risk drought on a roof terrace.  The unique micro climate and the combination of increased exposure and the lack of access to groundwater means that an irrigation system is almost a necessity for a roof garden, even if you don’t use it all of the time.  Just as important is drainage – all that water needs to go somewhere!  There are different systems you can use for both irrigation and drainage depending on the situation and your budget, so do consult an expert.

PLANT LIST - TOP 10 ROOF GARDEN PLANTS

 

Arbutus unedo
Trachycarpus fortunei
Stipa tenuissima
Pittosporum tobira 'Nanum'
Prunus lusitanica
Nandina domestica
Perovskia atriplicifolia 'Little Spire'
Pittosporum tenuifolium 'Golf Ball'
Agapanthus (any variety)
Pinus 'Marie Bregeon'
By Bowles & Wyer

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