The height of fashion
With space a real premium in metropolitan areas like London, roof gardens are becoming the buzz word on everyone’s lips – and it’s not as expensive to create one as you might think.

On the up and up
Roof terraces are on the up and up. Rarely has the demand for high-rise horticulture been more intense, particularly in London and other dense urban areas. The reasons are numerous. They range from the economic to the practical: sky-high property values in cities like London mean that traditional gardens are increasingly the preserve of the well-heeled, and the relative ease of maintaining a roof garden suits the lifestyle of workaholic urban professionals. The government’s twin ambition of increasing urban density while simultaneously improving the urban ecological balance, is also having an impact. But the real driver in the roof terrace boom is human ambition.

Regardless of spiralling property prices, it seems we’ll try almost anything in our quest for access to the elements. ‘Most existing roof terraces don’t have planning consent. They evolve gradually,’ says John Rice of London-based consultancy Urbanroofgardens Ltd. ‘First some decking gets put out on a balcony, then some planters are added, and eventually a full-height door replaces the window that’s been used as access.’ The end results are patchy, and in some cases, an accident waiting to happen.

Times are definitely changing
‘People resist investing in a proper roof garden because they assume that getting planning consent will be impossible. Then, once they’ve got it, they think it’ll be nightmare finding the right structural engineers, architects, garden designers, etc,’ says Rice. But it seems times are definitely changing. It appears it’s no longer the case that planning departments will bleat about overlooking and noise pollution before saying ‘no’. The role that roof gardens can play in increasing biodiversity, reducing the cost of heating through improved insulation and recycling rainwater run off, are increasingly taken into consideration.

Invest in your own quality of life
Further good news is that the cost of taking professional advice need not be prohibitively expensive. Assuming that no structural work is required to strengthen the roof, a planned and planted terrace can cost as little as £5,000. And it is generally estimated that outdoor space will add 10-15% to the value of a property. So even if the market’s a little flat, and you’ve no intention of moving for a while, why not invest in your own quality of life?

Of course there’s plenty of scope for spending a great deal of money on a roof garden. One cash drain is the use of high quality materials and top-class craftsmanship. Unlike traditional gardens, roof terraces have no respite from the weather. Wind, rain and sunlight all take their toll. To avoid wind damage, ensure that all surface materials and planters are well-made and securely fastened.

You must seek advice
Another consideration with potentially major cost implications is the strength of your roof. Can it cope with the added weight and permanent load of surface features? Before attempting any major work, it is vital to consult a structural engineer for advice. As a rule of thumb, the roofs of most existing residential buildings can withstand only minimal loads, wind and perhaps a little snow, but not much more. So, structural work may well be required. For former industrial buildings, it is unlikely that you’ll need to strengthen the roof, although you will need planning consent for change of use. Some new-build properties are built to accommodate roof gardens, but not all, so you must seek advice. If your engineer recommends the insertion of bracing or reinforced structural joints, you will need to adjust your budget substantially. It may be expensive, but it is money well spent, offering both peace of mind and the potential for a proper garden, not just a sprinkling of planters around the edges of the terrace.

Timber decking – not the only surface option, but by some distance the most popular – also has a vital role to play in spreading loads. But its most important purpose is lifting the garden off the rooftop to allow for drainage. The strategic placement of plant containers can also assist in vital irrigation. One of the most common ‘hidden’ costs is the complexity of accessing difficult-to-get-to rooftops. Dragging large planters and unwieldy decking up five flights of stairs is not for the faint-hearted. External lifts or pulleys may be your best option, but these don’t come cheap.

It’s tough at the top!
Finally, there’s the issue of what to plant. To a large extent the options are dictated by climatic conditions, but it’s also important to consider your commitment to maintenance-will you want to clamber on to the roof several times a week throughout the year to water and prune? It’s a good idea to find large ‘architectural’ perennials to complement the landscape. Desert species also thrive. They’re used to neglect and the extremes of the weather. It’s tough at the top!