Garden design made easy – Roof terraces and balconies

Whether you live in a house or flat, create a perfect outdoor area on the roof or a balcony by following Matt James' advice for a planting scheme for year-round interest.

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Matt JamesMatt James

Roof terraces and balconies provide a great opportunity to enjoy the surrounding views and extend the living space of your home, however small. It’s important to get the right mix of materials and planting for creating a space with year-round interest.

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Identify a design theme

Sleek and simple is the golden rule when designing a roof terrace or balcony. Cottage or rustic themes rarely work. Go for a simple, linear layout with contemporary materials such as polished stone, rendered walls, Cor-Ten steel or concrete, or traditional ones such as woven hazel and clay pavers using them in a modern way. Choose materials to complement patterns or colours in the surrounding landscape or adjacent buildings so the design blends in.

Whatever layout you choose, take account of the view. Eyesores, like gas towers and motorway flyovers, will need to be subtly screened, but if you have a sea view or attractive cityscape, make the most of it in your design. Organise your area to maximise good views, maybe framing them with tall container plants or pencil junipers.

Use decking

Decking is a good choice for a roof terrace or balcony because it’s warm underfoot, easy to work with and lightweight for carrying up several flights. Find decking at timbertechuk.co.uk. Any joists can be fixed to surrounding walls so the weight gets distributed to the walls and not solely to the roof itself. Choose western red cedar or hardwoods such as ipe or balau (from a sustainable source). They retain their colour, last much longer than softwood decks and look better too. If your roof terrace abuts a room with wooden flooring, use decking of a similar colour to help blur the boundaries between the two.

Most roof terraces are covered in a waterproof membrane, while others have a fireproof layer, so be careful not to puncture them with fixtures and fittings.

Coping with the elements

Wind is a common problem on roof terraces. Many plants can cope with it, but you might need some shelter if you want to enjoy the space all year. Unless there is protection from surrounding buildings, solid windbreaks aren’t a good idea as they block out the view, plus the wind stress on fixings is high. Instead, choose permeable trelliswork, hit-and-miss cedar battens arranged horizontally, or perforated sailcloth that filters the wind so only a subtle breeze is felt on the leeward (downwind) side.

Glass is commonly used as a balustrade and wind buffer on roof terraces as it provides uninterrupted views. Don’t site it across prevailing winds unless there are a few holes in it, otherwise turbulence will smack over the top and down on you with great force. Don’t put yourself at risk by teetering over high edges to fix screening – call in a specialist builder or a rope access company to tackle it for you.

Taller wind-tolerant shrubs offer some protection. Think of them as a living screen. Tough evergreens such as Olearia, Phormium, Pittosporum and Spotted laurel in big tubs are perfect for the job. Bamboo is worth trying too, except on very windswept roof terraces as its large leaves sway too much in the wind, which means the roots will shift about and the plants won’t establish in their new pots.

You’ll need protection from sunshine too. Shade sails are excellent – again, wind-porous materials are the best choice as you don’t want a solid barrier, with the risk of the fabric tearing or flying away. A cheaper solution is to put up a parasol, but make sure it’s securely anchored, otherwise strong gusts might blow it away..

A plain roof terrace transformed into a contemporary Eastern-style garden

Choose a planting scheme

Plants will have to be very tough to cope with difficult conditions. They’ll probably have to be tolerant of high winds and drought as well as strong sunshine or deep shade, depending on the aspect. Dense evergreen plants are good for year-round interest and most have thick, glossy leaves, which prevent them from drying out quickly. Griselinia, Garrya, Viburnum tinus, Escallonia, Euonymus, Fatsia and dwarf fan palms are ideal and provide shelter for colourful-but-tough perennials such as globe thistles, day lilies and Heuchera tucked underneath them.

On open roof terraces, plants must be able to cope with blazing sunshine. Choose plants such as thyme, lemon balm, sage, lavender, Potentilla, Olearia, Caryopteris, Californian lilac and dramatic Yuccas and Agaves. Grasses like hot conditions so they’re a good option as they create subtle texture. Miscanthus (try ‘Morning Light’ or ‘Flamingo’) are robust and stand tall; or for very exposed sites, choose Carex and Festuca varieties which form tight, low clumps.

Dwarf conifers, like pencil junipers and Pinus mugo ‘Mops’, tolerate hot, exposed sites too and couldn’t be better suited to roof terraces or balconies.

Alpines, whose natural habitat are clifftops and mountains, need little water and can bear extreme exposure to intense sunshine and strong winds. Place rows of terracotta bowls full of carpeting Sedum and Houseleeks – elegant and effortless.

Consider materials

Weight is the most important practical consideration. With tiny balconies tacked onto the sides of flats or townhouses, you won’t need to worry as they will have been specifically designed to take the weight of a few pots, containers and a bistro dining set. Roof terraces, however, are a very different matter.

Discovering the load-bearing capacity of a purpose-built roof garden is easy – you simply need to look at the title deeds. When it comes to older properties, chances are the space was originally intended to be somewhere to hang out the washing, or access the roof. How much weight it can take is debatable, and it’s likely you won’t find the information on the title deeds.

In order to be certain, consult a structural engineer who will calculate what you can – but more importantly what you can’t do – on an older-style roof garden. Find structural engineers at. Planters, plus plants, plus compost, plus water, plus paving, plus people can get extremely heavy, so it’s vital to get advice. Find structural engineers at istructe.org.

If weight is an issue, there are obvious things you can do. Plastic planters, along with fibreglass imitations, weigh much less than concrete, stone or terracotta containers. Avoid placing pots in the centre of a roof terrace and don’t have too many (fewer containers look better). Fixing pots to surrounding walls or placing them on cantilevered shelves will help as the walls will be taking the weight, not the roof. Also, choose lightweight collapsible furniture instead of a huge, glass-topped table.

Accessing the site

Access is another key factor that will affect what you can do with a roof terrace. You’ll probably need to bring materials and plants up in a lift and perhaps through the house, so always measure stairwells, corridors and doorways to check that you can easily manoeuvre plants and materials. Hoists, particularly cranes, are often expensive – so bear this in mind if your budget is tight. If access is really tight, you might have to tease apart trelliswork temporarily.

Keeping the space safe

Safety is of course paramount, so avoid hanging anything over the edge or placing pots on ledges, unless they’re firmly secured. Do check with your local authority though – some won’t allow you to do this. Pergolas, trellis, wirework or shade sails should be fixed securely, with the fixings easily accessible so that they can be tightened regularly. The balcony needs to be in good condition too – by law, the sides must measure at least 1100mm high, so you can’t fall over the edge.

Check out the regulations

Most flats are subject to strict covenants and regulations that must be adhered to. New roof gardens are often seen to be an extra floor, and if you live in a conservation area or in a listed building you’ll need to check any plans with the local authority. Even if a roof terrace is already authorised for garden use, many structures need permission from the property management company or local authority. Balconies are also under strict controls – some councils won’t even allow the railings to be painted a different colour. Check your title deeds or tenancy agreement for clarification or visit planningportal.co.uk for more information.

MAIN IMAGE HARPUR GARDEN IMAGES; PHOTOGRAPHS KATE GOULD GARDENS, ALISON HAMMOND