We’ve had the wonderful experience recently of designing a series of penthouse roof terraces at Chelsea Creek in London for London’s leading developer St George.   We thought we would share with you some of the key issues facing landscape designers when working on roof gardens. In essence many of the issues are identical to those facing ground floor garden designs, but there are a whole host of additional and quite technical issues that need to be considered when designing on an elevated level.  It’s a vast subject, so I plan to do a regular blog covering different aspects of roof garden design, in bite size chunks that are easily digestible.

It would appear at first that designing for roof gardens is very similar to normal garden design, however ultimately we found this just wasn’t the case.  One of our usual starting points in the creative design process would be to consider the views and vistas in and out of the garden, and how the garden will sit within the architecture of the building.  Straight away there were key differences to be understood.  We found a brand new dimension to consider: that of the view from street level up to the roof garden!  Of course this depends on whether it’s a 1st floor or a 20th floor roof garden, but either way, deep consideration needs to be given to the boundaries especially and the placement of any key features close to, or on the boundaries themselves.  Placement of a hardwood pergola close to the boundary needed to be rethought and re positioned further away, so as to avoid any issues that the planners might have had.  Hardwood slatted fencing which we introduced into parts of the boundary needed consideration to both sides of the fence, not just the internal aspect.  We had also positioned a green wall on a boundary, and once again we needed to efficiently design the back of this (without costing our client too much money), so that it wasn’t an eye sore when viewed from either street level, or an adjacent block.

Roof gardens are often (but not always) in urban locations with a heavy density of buildings, and another key issue we found was privacy and screening of ugly views to domineering buildings close by.  As landscape designers we feel that spatial design is one of the most important aspects of what we do and for this series of roof gardens it was essential that we carefully controlled the space, the views and the overall ambience of these terraces.  One of these roof gardens was sandwiched between a 7th floor garden and a 24th floor tower, and was on a slightly lower level, positioned on the 6th floor.  As you can imagine the space felt like a corridor, with a huge and potentially domineering tower on one boundary and totally overlooked on the other.  Spatially this garden was hugely challenging: we wanted the space to feel private and inviting and to feel as if it was a wonderful space in its own right, not a left over bit that was sandwiched between two others.  How did we overcome this?  We introduced horizontal screening at ‘ceiling’ level, we used a mix of topiarised ‘umbrella trees’ with flat horizontal canopies and introduced various styles of pergola.  One of the pergolas was designed in a beautiful hardwood with horizontal narrow slats to provide a ‘ceiling’ and block out the adjacent 24th floor tower.  The second pergola was a mix of hardwood and steel rigging which was designed with canvas sections that could be pulled across as necessary, to provide shade and privacy as required.  We also incorporated a stunning three metre high green wall which spanned the full length of one boundary. Centrally positioned within this green wall was a magnificent steel and Corten water feature. By introducing such a dynamic feature statement the eye was naturally held within the garden space and not allowed to travel upwards and out of the garden.  Usually with Roof Terraces we like to encourage the views up and out of the garden to the sky and beyond but the challenging nature of this space meant that we had to work hard to focus the attention to directly within the garden space itself.  It was only on the narrow boundaries (NW and SE), where there were some pretty stunning views out across London’s skyscape, that we positioned lounge seating and funnelled the users view out across this magnificent view.

On another of the roof gardens, we incorporated a fully automated louvred aluminium pergola, of sizeable dimensions, to provide a really cosy private space.  Ultimately we called it ‘the snug’ – it became a real outdoor lounge that included an outdoor limestone fireplace providing not only a focal point, but also warmth and ambiance to boot.

If the roof garden isn’t heavily overlooked by neighbouring buildings or gardens, it is well worth exploiting the proximity of the roof terrace to the sky.  We had a lot of fun designing ‘The Tower’ on the 24th floor as it commands such breath taking views down across London and provided us with plenty of scope to be innovative. We also loved the connection with the sky and used this as an inspiration for the material choices and colour scheme that ran throughout this garden.  During the day the roof terrace is full of neutrals, and the materials are a blend of off white and steel, with white and blue contemporary planting.  At night we designed a magical midnight blue lighting scheme which connects visually with the night sky above and provides a very dramatic backdrop to the penthouse itself.  If you can use the sky within the design of the roof terrace then do; for us it had a feeling very much akin aesthetically to the design of a coastal garden. 

It probably goes without saying, but the one thing you can’t do on a roof garden is excavate – the only way is up!  The challenge here is that we didn’t want to end up with a roof garden that looked like it was paving with a series of planters just sat on top.  We wanted a unified and fully integrated design so that the planters were not separate and standalone items – we designed the roof gardens so that the planters became an integral part of the scheme.  For the first series of roof terraces we designed the planters in Corten Steel, we incorporated other features using this material (outdoor fireplaces, sculpture, water features etc) and then in addition also included rust coloured planting to provide true cohesion.  The planters have been designed in a very linear style and this has then been continued across all of the paving and decking details. It is this linearity that we believe finally gave the scheme a totally unified look.

Roof gardens are pretty much always in close proximity to the building itself, and it becomes therefore even more important than usual to integrate well the garden scheme with the interior space.  Views from inside out leave little space to hide so considered spatial planning becomes a little like completing a Rubik’s cube: trying to ensure good flow and movement externally whilst still ensuring that the views out are attractive and continually exploring the best maximisation of space while providing the optimum aesthetic is both time consuming and requires well-honed design skills.  Roof terraces, by nature, tend to be relatively small spaces and it is an art in itself to be able to incorporate a mix of features without ending up with a real mess!  There are no ‘left over spaces’ every inch of the roof garden is spoken for and has to earn its keep. Then again, trying to create ‘space’ that provides a breather, and a backdrop to the features included is an essential requirement.  Without this space it can all appear a little overcrowded and crammed in.  The Chelsea Creek Roof terraces had a wide range of features that had to be incorporated regardless of whether the terrace was 100 metres or 300 metres square and this proved challenging to say the least.  Introduction of ‘screens’ to divide areas allowed us to compartmentalise the space, thus allowing more to happen in a smaller space.  These screens were a combination of planted screens such as hedges, green walls and taller evergreen planting combined with slatted hardwood panels.  The roof terraces were zoned into lounge, kitchen, hot tub and open areas and it was necessary to carefully consider and control the flow and views as one moved from one area to another.

Finally, level changes which are so sought after in ground level gardens prove highly expensive on roof terraces and on balance are probably not worth exploring unless there is plenty of roof build up naturally to work with.  An increase in level within the garden provides issues on the boundaries (minimum 1100mm) and ultimately we gave it a miss, and used other design elements to provide the interest and impact that we were seeking.



Images from Chelsea Creek Dockside Roof Terraces, project by Aralia and Central St George PLC