Repair Systems — 01
Drainage cell systems — planter boxes and podiums
Technical product reference for modular polypropylene drainage cell systems used in planter box, green roof, and podium slab waterproofing remediation on Australian Class 2 strata buildings. Covers depth selection, void ratio, compressive strength, water retention cups, passive irrigation, filter fabric pairing, and brand comparisons.
What are drainage cell systems?
Drainage cells (and cuspated drainage membranes) create a high-void sub-surface drainage layer over the membrane in planters, podiums, green roofs and behind retaining walls. The modular cells channel water to an outlet while a filter fabric over the top keeps soil fines out of the void; some cells also retain water for green-roof irrigation. They are a drainage layer, not a waterproofing membrane, and need a protection layer between the cell and the membrane below. Selection turns on the cell height (drainage void and any water storage), the compressive load capacity for the build-up above, and the filter / membrane interface.
Product Reference
Individual products — one card each — scroll to view all
Atlantis
Atlantis Flo-Cell
Modular drainage cell for podiums, planters & green roofs
Atlantis Flo-Cell is a modular recycled-polypropylene drainage cell that creates a high-void sub-surface drainage and water-storage layer over the membrane in planters, podiums and green roofs. Confirm the cell height and compressive capacity for the build-up with Atlantis.
Elmich
Elmich VersiDrain
Drainage & water-retention cell for podiums & green roofs
Elmich VersiDrain (and the VersiCell range) are recycled-polymer drainage and water-retention cells for green roofs, podiums and planters, providing a drainage layer over the membrane with optional water storage. Confirm the model, height and load capacity with Elmich.
Geofabrics
Geofabrics MegaFlo
Geocomposite / strip drain for sub-surface drainage
Geofabrics MegaFlo is a geocomposite drainage product combining a polymer drainage core with a bonded geotextile filter, used for sub-surface and sub-soil drainage behind walls, in planters and under landscape build-ups. Confirm the product and flow capacity with Geofabrics.
Newton Waterproofing
Newton Geodrain
Cuspated drainage membrane for walls & decks
Newton Geodrain is a cuspated (dimpled) HDPE drainage membrane, typically with a bonded geotextile filter, providing a combined drainage and protection layer over structures and membranes on walls, decks and planters. Confirm the model and the Australian distributor for the application.
Cordek
Cordek Cellcore / Drainage Cell
Void former / drainage cell for structural build-ups
Cordek supplies drainage cells and void formers in recycled polymer for drainage and void layers in structural and landscape build-ups over the membrane. Confirm the product, cell height, load capacity and the Australian distributor.
System Comparison
Drainage cell systems — confirm all selections against the current manufacturer TDS before specifying.
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Filter fabric is mandatory above every drainage cell installation — without it the cells will clog and fail
Geotextile filter fabric must be placed over the full surface of the drainage cell layer — covering every panel and lapping up the planter box walls — before growing medium is placed above. Without filter fabric, fine particles from the growing medium migrate down into the drainage cell void with each irrigation and rainfall event, progressively clogging the drainage paths. Once clogged, drainage cells cannot be cleaned or restored — the growing medium and cells must be completely removed and replaced. Filter fabric is not optional and is not a value-engineering reduction — it is a mandatory component of every drainage cell installation. See the Filter Fabric page for geotextile filter fabric specification and selection.
Drainage cells must be installed above a correctly waterproofed and inspected membrane — not as a substitute for waterproofing
Drainage cells are a subsurface drainage product — they sit above the waterproofing membrane and manage the movement of water within the planter box system. They are not waterproofing products and do not protect the structural slab from water ingress. The waterproofing membrane below the drainage cells must be correctly specified (root resistant where plants are to be grown above), correctly installed, flood tested, and confirmed defect-free before the drainage cells are placed above it. Placing drainage cells over an uninspected, defective, or non-root-resistant membrane will not prevent long-term water ingress into the structure below. Confirm the waterproofing membrane specification on the Root Resistant Membranes page before specifying drainage cells.
Confirm structural loading with the engineer before specifying a planter box system on an existing podium slab
On existing Class 2 strata podium slabs and roof decks, the structural capacity for a new or replacement planter box system must be confirmed with a structural engineer before the system is specified. The combined dead load of the waterproofing membrane, protection board, drainage cells, filter fabric, growing medium, and plant material must be within the slab's design load capacity. Even with drainage cells substituting gravel (98% weight saving in the drainage layer), the growing medium and plants impose significant dead loads — particularly where deep-rooted plants or trees are specified. Older podium slabs may have been designed for minimal or no planting load. Do not assume an existing slab can carry a new planter box system without engineering confirmation.
Drainage cell depth selection — confirm with the hydraulic engineer and landscape architect before ordering
The correct drainage cell depth (20mm, 30mm, or 50mm) must be confirmed against three criteria before ordering: the hydraulic design flow rate required for the drainage area and rainfall intensity, the available build-up height within the planter box (membrane surface level to the top of the planter wall), and the compressive strength required for any machinery access. These three criteria are rarely all equal — the deepest available cell is not always the correct specification. A 50mm cell that exceeds the available build-up height leaves insufficient depth for growing medium. A 20mm cell that cannot handle the design rainfall flow rate will cause waterlogging above the cells. Confirm depth selection with the hydraulic engineer and landscape architect before placing the order.
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer technical data sheet, project specification, hydraulic design flow rate, drainage cell compressive strength requirements, available build-up height, structural loading confirmation from the engineer, landscape architect planting specification, and NCC requirements. Geotextile filter fabric is mandatory above all drainage cell installations. Drainage cells are subsurface drainage products and are not waterproofing — the waterproofing membrane below must be correctly specified, installed, and flood tested before drainage cells are placed above. Do not rely on this reference as a substitute for professional hydraulic engineer, structural engineer, landscape architect, or waterproofing consultant advice.