Type IV


CSI Specification: Type IV (DOCX)  -----------------
CSI Specification: Type IV (PDF)

waterproofing system

This three-course assembly involves a layer of fine growing media over two layers of a granular mineral drainage media. A root-permeable separation fabric separates the growth media from the granular media layers and keeps the growing media fines from mixing with the granular media. The roof drains and pitches are manipulated to pond water inside the lower layer. The depth to which water may accumulate in this zone is typically 1 to 3 inches ( 2.5 to 8 cm). During the growing season, a constant water level is maintained by an automated valve. The retained rain or irrigation water in this lower granular layer performs just as a perched water table does in nature. The upper granular layer (above the water storage layer) facilitates drainage. Typical assembly thicknesses range from 6 to 10 inches (15 to 26 cm). Type IV assemblies are ideal for supporting turf and biodiverse meadow and woodland landscapes. Type IV green roofs promote strong plant growth by draining and distributing water efficiently and concentrating the root mass in a stable temperature and moisture zone. Irrigation is provided by a highly efficient base flood system that introduces water at the root level, an approach that minimizes water loss due to evaporation and promotes deep root development.

Typical Type IV profile:

  • wind erosion stabilization system
  • growth medium
  • root-permeable separation fabric
  • thermal shield (for semi-arid climates)
  • light-weight granular drainage media
  • light-weight granular drainage media (water storage layer)
  • protection fabric
  • root barrier membrane (when required)
  • waterproofing system

Data Sheet

Type IV Data Sheet

Case Studies

Oaklyn Branch Library, Evansville, IN