How to design a rooftop garden

Live in a high-rise block and dreaming about a garden? Follow our expert practical advice and design your perfect roof garden

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If you live in the city, it's more likely than not that you don't have a garden. Having an outside space always comes at a premium in urban areas, and if you live in a tall building or block of flats, you may simply be too high up to be anywhere near a garden. Unless you live on the top floor and have access rights to the roof. Or perhaps you have your own roof terrace you're yet to put to use? 

Roofs provide excellent opportunities for creating a garden, and can be made as attractive and relaxing as their ground floor counterparts. Follow our advice on everything from structural considerations to planting and lighting schemes, and become the proud owner of a chic rooftop retreat. 

Is my property suitable for creating a rooftop garden?

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 the Institution of Structural Engineers

Planters, plus plants, plus compost, plus water, plus paving, plus people can get extremely heavy, so it’s vital to get advice. 

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 garden furniture instead of a huge, glass-topped table.

Read more about container gardening for small spaces.

Are there building regulations for rooftop gardens?

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.

Planning access and safety of your rooftop garden

Access is another key factor that will affect what you can do with a rooftop space. 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.

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.

Factor in wind when designing a rooftop garden

Wind is a common problem in rooftop gardens. 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.

Choosing a rooftop garden design scheme

Sleek and simple is the golden rule when designing a rooftop garden. 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.

Outdoor lighting can be a very effective addition to a rooftop garden design scheme. Plan your lighting with the specifics of the rooftop location in mind, avoiding designs that are lightweight and flimsy, as they will most certainly be ripped off by strong winds. Consider built-in wall lights instead; if you still want the dreamy ambience of fairy lights, choose ones that are on the heavier side, and position them in a sheltered corner above seating, or attach them to a wall. 

Lakeview Rooftop + Garden project by dSpace design studio

Different types of outdoor lighting are used to create lit-up zones as part of the Lakeview Rooftop + Garden project by dSpace design studio

(Image: © dSpace Design Studio)

Choosing the best flooring material for a rooftop garden

Choosing the flooring material for your rooftop garden can be approached in much the same way as choosing flooring for other outdoor spaces; the choice should be dictated by the size and style of the space, as well as your personal preference. Stone or terracotta paving will work in smaller spaces – tiles are your best bet for ease of transporting on to the roof and installation. 

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. 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 create a link between inside and outside.

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.

Find out how to install decking

Lakeview Rooftop + Garden design project by dSpace

Decking is used as part of the stunning Lakeview Rooftop + Garden project by dSpace Studio

(Image: © dSpace design studio)

Choosing 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.

Walk on glass rooflights by Roof Maker

A container garden on a rooftop terrace featuring Walk On Glass Rooflights by Roof Maker

(Image: © Roof Maker)

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