A root-resistant layer limits root penetration towards vulnerable parts of a green-roof system. Its function must suit the selected planting and other roof layers.
What does this mean on your roof?
The term does not mean any loose membrane is suitable. Root resistance may be provided by a suitable waterproofing product or by a separate system layer.
Ask which arrangement is proposed and how continuity is maintained at seams, edges and penetrations. Interruptions particularly need coordinated details rather than assumptions based on the open surface.
For an existing roof, establish which covering is present and whether it can remain within the new system. An unidentified older layer does not acquire root resistance simply because planting is added above it. Record materials and junctions before vegetation conceals the roof. Include access for investigation and repair in the initial arrangements, not only after a problem occurs.
Frequently asked questions
Is every waterproof membrane root-resistant?
No. Check the intended application and product properties within the system.
Can the existing layer remain without investigation?
That cannot be assumed. Material and condition need to be established.
Consulted 19 September 2026. Check requirements for your own address and selected system.