Roof garden design often have a distinct set of practical and aesthetic considerations. Planting is always tricky, as there is no soil to dig into and you need to think about weight and accessibility when choosing plants and planters. You may be able to find details of weight loading limits in the deeds or documents associated with the property, particularly if it is a new build, however if you live in a period property such information may not be available. If you have any concerns it would be advisable to employ the services of a structural engineer or surveyor.
If you are creating a space on a roof or balcony which has not previously been accessed, your local planning department may want to check whether it overlooks neighbouring properties or obstructs their view. To prevent potential problems down the line, it is worth making contact with the council before any building works commence. This is where using a garden designer can be beneficial, as plans and visuals can be created that will help in any planning application.
A safety barrier is an essential part of any roof garden or balcony. If one already exists, it is important to check that it is still sound and complies with current building regulations. If you require a new barrier, it is advisable to get it installed by a professional. It’s also worth thinking about practical and aesthetic considerations. Glass or other transparent materials are preferable if the balcony has a good view. Railings can also be useful for preserving a view, but if the site is exposed a solid barrier would be more beneficial as a wind break.
All plants will need to be in containers and will require their own watering system, unless you are happy to give them lots of attention during hotter, drier months. As there may be weight issues it is prudent to go for a reasonably lightweight container such a fibreglass or metal. Mix LECA (Lightweight Expanded Clay Aggregate) pellets with your container soil to increase its water retention while decreasing the weight.
Choose plant specimens that work well in exposed, elevated environments. There is no point in using plants with a delicate blossom if after the first gust of wind they lose all their flowers. In the garden shown here we used robust Cordyline Australis that lend a strong architectural appeal to the space. Look at coastal plants for inspiration, as these are usually hardy and can withstand extreme conditions. Grasses and perennials are a good choice for maximum impact in the summer when the garden is most likely to be in use.
For this particular garden there were restrictions imposed by the building managers which prevented us from altering or attaching anything to the fabric of the building. The restrictions meant that we had to be creative with our lighting choices, as the majority of light fittings do need installing on or in a surface. We relied heavily on illuminated furniture and planters, which happily have a very dramatic impact in a small space. In your roof terrace, try to use lighting to illuminate individual features. Up lighting works fine, but only to illuminate specific objects – it will be wasted if it is simply shining into the night sky. Accentuate features by edging them with rope lights or weatherproof LED strips. It can be quite effective to install lights in cut-outs in your deck and cover with coloured Perspex panels or a glass mulch.
It is important not to penetrate existing surfaces. Compromising the integrity of a balcony or roof terrace floor could lead to expensive water damage to the building below. There are flooring systems on the market which are designed specifically for roof terraces and will allow dry and elevated installation without creating pockets where water can puddle. Lightweight stone, decking and decorative mulch tend to serve roof gardens the best. Here we mounted Yellow Balau decking on a shallow timber frame, using rubber joist supports to raise the frame slightly off the floor to aid drainage without damaging the surface.
In-built benches help break up the space and define areas without it feeling cluttered. Make them big and luxurious and they can also double as loungers. Box really clever and they could also be hinged allowing space to store cushions or other outdoor items.