A fascinating opportunity came to us at the end of 2021 to design our first-ever office roof garden.

The brief was to create a commercial breakout space for staff at a corporate headquarters in Berkshire. The five-storey office building was triangular in shape, and the roof area was divided into three spaces: one facing southeast, one southwest and one facing north. Each space had its own climatic and aspect differences, too – not to mention the whole thing was five floors up and therefore very exposed to sun and wind.

When I first visited, the breakout areas were little more than wooden picnic benches and some artificial turf (see below), albeit with a view of Windsor Castle in the distance. The client requested a sustainable, colourful and engaging space to eat lunch or take a break and wanted to include some enclosed pods for business meetings. They also needed outdoor benching and planting.

Office roof garden before shot
Office roof garden before shot

Challenges of building an office roof garden

Planting on a roof comes with lots of challenges – first and foremost – there is no soil.

The weight of the planters and the soil must be considered structurally safe for the building. Careful thought has to be given to the extra loading caused by adding additional frameworks, structures and surfaces, as well as the planting and the people who will use it. So, consulting a structural engineer is vital if you are thinking of creating a roof garden on a flat roof.

All the plants in a roof garden must be self-contained. We used lightweight soil substrates over a filling layer of expanded polystyrene or clay particles. When wet, the water can run out quickly and does not create damp soil within the planting zones (which is good for the plants) and keeps the weight down (which keeps the structural engineer happy).

Being used by up to 40 people at a time, the surfaces and benching needed to be hardwearing and fixed so that they were good to go for years to come.

On this project, we were lucky to work with a very experienced team at Hedera Screens, who have completed many such projects before.

office roof garden
custom designed rooftop breakout spaces
Bespoke rooftop meeting pod with living roof
The Hedera Screens team installing the office roof garden

The roof garden design scheme

Working with Hedera Screens, we chose composite deck board and cladding for the bespoke meeting pods, with hardwood timber cladding for the walkways and Hedera’s own green screens and walling, which provide interest, protect from the wind, and screen from the neighbouring buildings. The bespoke planters were of fibreglass construction, produced in the company colours.

Hedera fitted the meeting pods with living roofs – sedum matting with an irrigation system hidden inside one of the bleacher-stepped seats.

When choosing plants for roof terraces, they must be tough and wind hardy. We chose the small tree Amelanchier lamarkii in a multistem form, a mix of herbs, evergreen Libertia grandiflora and Liriope muscari, Pinus mugo, Polystichum setiferum ‘Herrenhausen, Euphorbia ‘Humpty Dumpty’, Stipa tennuissima, Phormium ‘Tricolour’ and Heuchera ‘Obsidion’, flowering Geum ‘Totally Tangerine’, Geranium ‘Rozanne’ and Penstemon ‘Garnett’ to bring long-lasting colour and interest to the planters.

The vertical planting included ivy green screens, and in the vertical planter boxes: Heuchera species in different colours, Alchemilla mollis, Bergenia, Carex, ferns, Pachysandra and Helleborus.

Overall the effect has been worth all the hard labour, including difficulties with planning and access. We know the clients are thrilled with the result.

Since this project, we have designed another roof terrace closer to home in Leicester, which is currently under construction. We’ll show you that one once it’s completed.

If you are looking for an innovative solution to your commercial space, whether on the roof or the ground, we’d be happy to help. Call us on 01530 449 400 or use the contact form below.

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