Our design team share their insights into what you need to consider when installing a roof garden…
1. WHAT TYPE OF ROOF GARDEN DO YOU WANT?
In horticultural terms, there are intensive and extensive roof gardens. Extensive gardens are essentially ‘green roofs’ – they have very thin soils and are not intended for human use. Meanwhile intensive roof gardens have much deeper soils, along with irrigation, a variety of plant types, and the possibility for paving and seating areas. You’ll need to think carefully about which type would best suit your space and your needs.
2. KNOW YOUR RIGHTS
Don’t fall into the easy trap of assuming that you have automatic usage rights for your roof garden. Planning consent may well be required to use a roof space – especially when it hasn’t been designed with access, or where it’s a flat surface, or where it’s been newly created. Local authorities are particularly focused on the issue when the property is in a conservation area or if there are potential issues of overlooking or noise.
3. CHECK THE ENGINEERING
If you opt for an intensive roof garden, we’d recommend getting a qualified engineer involved to calculate the load-bearing weight potential – this is something you don’t want to get wrong! Engineers will make an allowance for the weight of people and furniture on the terrace, as well as allowances for wet compost and the weight of the plants themselves.
4. KEEP IT SIMPLE
In terms of design – keep it simple! The tendency is always to try and stuff too much into these spaces. Consider how the roof terrace will be used and plan accordingly – and as flexibly as possible. Use high quality features and materials, then position and light them carefully.
5. LOGISTICS ARE KEY
As you might expect, the logistics of constructing a roof garden is more challenging than one on ground level and access for construction can be a key constraint on the build. If you’re building at 1st, 2nd or 3rd storey, a furniture lift could be a useful method for moving materials in and out of the space. If you’re constructing higher than this, then you’re most likely looking at the crane option, which can be very expensive.
6. A ROOF GARDEN HAS A UNIQUE MICRO-CLIMATE
The combination of increased exposure and lack of access to groundwater means that plants frequently risk drought. Therefore, irrigation is almost always a necessity – even if you don’t use it all the time, it would be wise to seek the advice of an expert on this. Just as crucially, all that water then needs to go somewhere! Drainage is an important issue on roof gardens – and again one that requires expert advice to avoid problems in the future!
7. ROOF TERRACES ARE EXTREME ENVIRONMENTS
Sunny, windy, dry – a roof garden is generally very exposed and not unlike a seaside micro-climate. Whilst maritime plants don’t suit every space, the point is to ensure the planting works with the environment, rather than against it. Whilst olives or tamarisk can survive fairly radical exposure, beware of the ‘windsail’ effect of trees and make sure the containers are sufficiently sized to stop them blowing over.
Now we’ve shared a little of our expertise – but we’d be happy to help you with any roof garden projects you might have in mind. You can find out more about what we offer here!