Step 1 - Foundation

Here perhaps the most important thing is weight.

Roof gardens can weigh anything from around 80kg/m² saturated for a very basic EXTENSIVE roof garden build up to several tons for an elaborate INTENSIVE build up, so the supporting structure has to be carefully designed.

Always work on saturated weights.

As a rule of thumb most timber and metal roof decks will be suitable for a basic extensive roof garden and will either have to be reinforced or changed to concrete for the heavier intensive roof gardens, but a structural engineer should provide confirmation.

Another important factor to consider at this stage is the design falls to allow rainwater to run off.

The temptation is to cut back on the drainage requirements as it is assumed quite correctly that the roof garden will absorb much of the rainwater, indeed this is one of the benefits, but it is considered good practice to design to the worst case scenario where the roof garden is completely saturated and the roof therefore needs to be able to discharge the excess water normally, otherwise damage could occur due to the extra load or water discharging where you don't want it to.

There are exceptions to this where zero falls one designed as part of the irrigation system. See Step 7.

We provide rainwater outlet requirement calculations. See technical services.

Next Steps to Construction

• Step 2 - Root Barrier
• Step 3 - Protection Fleece
• Step 4 - Drainage/Reservoir Boards
• Step 5 - Filter Fleece
• Step 6 - Growing medium and planting
• Step 7 - Irrigation
• Step 8 - Finishing Components
• Step 9 - Roof Garden Safety