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Inverted System

Firestone EPDM Inverted System


The Firestone EPDM Inverted System is a variation of the conventional Ballasted System. It is ideal for roofs with regular traffic or in severe weather climates. It can be applied on any building that can accommodate the extra load of the ballast and where the roof slope does not exceed 10%.


  • Low installation cost
  • Use of large EPDM sheets
  • Fewer seams
  • Fast installation
  • Large choice of compatible substrates
  • Extra durability
  • Flexibility for upgrading of insulation in reroofing projects


EPDM sheets are loose laid over an acceptable substrate. Adjoining sheets are overlapped a minimum of 100 mm and the seams are spliced with Firestone QuickSeam Splice Tape. Once roof perimeters and penetrations are flashed in accordance with Firestone specifications (PDF), a layer of extruded polystyrene and a geotextile are placed over the membrane. The total system is held in place using one of the following materials as ballast:

  • Gravel in form of round, smooth, river washed aggregate without broken pieces (nominal 16 to 32 mm).
  • Concrete pavers with smooth trowel finish (min. 50 mm thickness).
  • Crushed gravel that must be graduated.

Prior to selection of this system, the specifier should evaluate structural conditions of the building to verify its load bearing capacity. Roof slopes and wind requirements should also be investigated.