A roof is no longer just a roof. It is usable floor area — but only if the load, the drainage and the irrigation are solved before the first plant arrives. Most failed green roofs failed at the build-up, not at the planting.
Seven green roof build-ups, chosen by what the roof has to do
We specify the system against structural capacity, water strategy, access and the planting you actually want on top:
- Standard extensive green roof — lightest build-up, sedum, no regular access
- Premium extensive green roof — deeper substrate, herbs and grasses, more biodiversity
- Water retention extensive green roof — buffers rainfall before discharge
- Standard intensive green roof — a real garden: shrubs, small trees, walkable
- Water retention intensive green roof — intensive planting plus stormwater buffering
- Standard parking deck — green over trafficked structure
- Water retention parking deck — trafficked, planted and buffering
What a rooftop garden earns its owner
Rooftop planting cuts the urban heat island effect, insulates the building in both directions, buffers stormwater away from the sewer at peak, extends the life of the waterproofing by shielding it from UV and thermal cycling, and adds habitat in places where ground-level space is gone.
The part clients tend to value most is the least technical one: it turns dead square metres into somewhere people want to be. The rooftop garden at Ebben Inspyrium in Cuijk is a working example.
Designed with the structural engineer, not after them
Saturated substrate weight, wind uplift at height, root barriers, drainage layers, fall protection, irrigation supply and winter maintenance access all have to be agreed with the building's engineer before the planting plan is fixed. We do that first, then design the garden inside the envelope that survives it.
Wind is the factor most often underestimated. Conditions on a sixth-floor terrace are not the conditions in the street below, and a planting scheme drawn at ground level will shred in its first winter. Species selection, staking, substrate stabilisation and shelter planting all change with height and exposure.
Planting that lasts on a roof
- Species chosen for wind exposure, drought stress and shallow root runs
- Substrate specified by weight and water-holding capacity, not by the bag
- Irrigation with a reliable supply and a controller someone will actually use
- Root barriers and drainage layers that protect the waterproofing beneath
- Edge detailing, fall protection and safe maintenance access
- Containers, raised beds and structural planters where the deck cannot carry a full build-up
- A maintenance regime handed to the building manager in writing
Roof, terrace, deck or campus
The same principles scale from a single roof terrace to a whole site. At the Trespa® campus in Weert the green strategy ran across roofs, ground level and the spaces between buildings as one plan, which is usually where a green roof stops being a compliance item and starts being worth the money.
Frequently asked questions
What is the difference between an extensive and an intensive green roof?
Extensive roofs have a shallow, light substrate, low-growing planting such as sedum, and are not designed for regular access. Intensive roofs carry deeper substrate, larger planting and people — they are gardens, and they weigh considerably more.
Can any roof carry a rooftop garden?
No. Structural capacity for saturated substrate weight is the first check, and it decides which of the build-ups is available to you. That assessment comes before any design work.
Do you supply the system as well as the design?
Yes — design, material supply and realisation, including irrigation and planting.
Projects we have delivered
- Rooftop garden Ebben Inspyrium, Cuijk (Netherlands)
- Green campus design Trespa®, Weert (Netherlands)
Send us the roof
Structural drawings and the load capacity are enough for a first answer on which build-up your roof can carry.