A complete green roof system, from the substrate to the plants

Whatever the type of system (intensive, semi-intensive or extensive), the different materials making up the green roof build-up are successively laid over a waterproofing membrane serving as a root barrier in a configuration consisting of the following layers, from the bottom up:

  1. A drainage layer (different materials may be used)
  2. A filter layer
  3. A growing medium (substrate)
  4. A layer of vegetation (planted by sowing seeds, cuttings, or laying pre-grown mats)
  5. A sterile (non-vegetated) area must be laid around the edge of the roof, as well as around any features requiring a waterproofing upstand.

végétalisation de toiture - coupe type
The drainage layer and growing medium may be of very different thicknesses from one system to another. Each configuration must specify the thickness required for the different materials, and also the load at maximum water holding capacity (MWC) represented by the system.

Case of extensive green roof systems (lightweight, low-maintenance):

Special configurations may also be proposed by the designers of green roof systems depending on the specific parameters of the project:

  1. Use of pre-grown mats (rolls or tiles) directly on the substrate
  2. Single-layer configuration (a single material serves as the drainage and the growing medium)
  3. Configurations specific to pitches over 20%, requiring retention or anti-erosion systems.

Types of vegetation

sédum acre

sédum album

sedum floriferum

Sedum acre

Sedum album

Sedum floriferum

sedum hispanicum sedum kamtschaticum sedum reflexum

Sedum hispanicum

Sedum kamtschaticum

Sedum reflexum

sedum sexangulare sedum spectabile sedum spurium

Sedum sexangulare

Sedum spectabile

Sedum spurium

The plants generally (but not exclusively) used are plants from the Sedum genus. This genus belongs to the family of Crassulaceans and includes over 400 species of succulent plants. Sedums (or orpines) are entomophilous, pollinated by insects and therefore not listed as allergenic (cf. RNSA). They are rock plants that store water in their leaves and give star-shaped flowers with 5 branches (sometimes 4 or 6). The most common Sedums used for green roofs are: Acre, Album, Floriférum, Réflexum, Sexangulare, Spurium. For more information, visit these sites:

- INPN site (National natural heritage inventory) and the specific page on Sedums

- Telabotanica site

- AIAB site (Association for IT applied to botany) and specific page on Sedums

- RNSA site (National aerobiological surveillance network) concerning pollen allergies