Waterproofing green walls
Waterproofing is project-dependent; in some cases there will be a sufficient air gap between the back of the planting system and the wall, making waterproofing treatment unnecessary. The air gap prevents movement of water between the wall and the planting system, and air-prunes pl
ant roots to reduce the risk that they will directly contact the wall and provide a path for movement of moisture. Provision for an air gap between the planting system and the building wall will also prevent growth of mould. Where waterproofing is necessary, it will prevent damage to the wall from moisture and dissolved salts from fertilisers. In some cases the supporting wall might be considered waterproof as is; for example, a preformed concrete wall may be thick enough to be rated as fully waterproof, or a wall constructed from marine-grade plywood will have some degree of waterproofing from the glues used within the ply. Consideration must be given to waterproofing penetrations to the wall as well as junctions between surrounding fascia (if used) and junctions between wall waterproofing and drip trays (see box). Roller-applied liquid waterproofing treatments can be used on internal and external green walls. When considering waterproofing for any green wall, seek advice from a waterproofing consultant to ensure the most suitable treatment is chosen.
The manufacturing and installation of waterproofing membranes should comply with the Australian Standard for membranes used to waterproof exterior areas of buildings (AS 4654.2-2012 Waterproofing membranes for external above ground use – Design and installation). Waterproofing membranes used for internal walls should be manufactured and tested to AS/NZS 4858:2004 Wet area membranes. Waterproofing treatment should follow the procedures used in other internal areas of residential buildings, such as bathrooms, kitchens and laundries. These are specified in AS 3740-2010 Waterproofing of domestic wet areas.