Green Roof Questions, Answered

The exact build-up depends on the roof and planting design, but a typical system may include:

1. A suitable structural roof deck
2. Primary waterproofing
3. Root barrier, where required
4. Protection fleece
5. Drainage or drainage-and-storage membrane
6. Filter layer, unless already bonded to the drainage membrane
7. Green roof growing substrate
8. Vegetation
9. Edging and pebble borders

Not every roof requires every separate product. Some drainage membranes combine drainage, water storage and filtration in a single layer.

The right choice depends on how much water the planting needs, the roof build-up and the expected loading.

As a general guide:

• Shallower membranes suit straightforward drainage and lighter extensive systems.
• Drainage-and-storage membranes retain useful water for vegetation while allowing excess rainfall to escape.
• Deeper, stronger membranes suit intensive planting, heavier substrates and more demanding landscaping applications.

Choosing the wrong membrane can leave you with either too little water retention or unnecessary weight and cost. Contact the technical team with details of your roof and planting if you need help comparing options.

Shop green roof drainage products:  https://urbangreenroofs.com/collections/green-roof-drainage-water-storage

A separate root barrier may be required where the primary waterproofing is not certified as root resistant.

It protects the waterproofing and roof structure from roots growing into vulnerable joints or materials. This is particularly important where more vigorous vegetation is planned.

Check the specification of the existing waterproofing rather than assuming it already provides adequate root resistance.

They perform different jobs.

Protection fleece is normally installed beneath the drainage layer to help protect the waterproofing or root barrier from light mechanical damage.

Filter fleece is installed above a drainage membrane to stop growing substrate and fine particles from entering and blocking the drainage spaces.

Some drainage products already include a bonded filter layer, so a separate loose filter fleece may not be required directly above them.

Sedum trays provide an established planted finish and can create a more immediate visual transformation. They are a good option when you want the roof to look complete soon after installation.

Wildflower seed is a lower-cost way to establish varied planting over time. It requires suitable substrate, careful sowing and more patience while the plants develop.

Your choice depends on budget, the appearance you want and how quickly you would like the roof to become established.