Repair Systems — Protection & Overburden
Filter fabric systems — planter boxes and podiums
Technical product reference for geotextile filter fabric systems used in planter box, green roof, and podium slab waterproofing remediation on Australian Class 2 strata apartment buildings.
What are filter fabric systems?
Non-woven geotextile filter fabrics sit over a drainage cell or gravel layer to let water through while holding back the soil fines that would otherwise clog the drainage void. They also separate the growing medium from the drainage layer and can cushion / protect the membrane and drainage layer from the build-up above. A filter fabric is a geotextile, not a waterproofing membrane or a root barrier. Selection turns on the geotextile grade (by mass) for the soil, flow and protection duty, matching the fabric to the drainage layer it sits over, and adequate overlaps at the joints.
Product Reference
Individual products — one card each — scroll to view all
Geofabrics
bidim Geotextile
Non-woven needle-punched geotextile (filter / separation)
bidim is an Australian-made non-woven needle-punched continuous-filament geotextile used for filtration and separation over drainage layers, available in graded ranges (A14, A19, A24 and up) by mass. Specify the grade for the soil, flow and protection duty with Geofabrics.
Geofabrics
Polyfelt TS Geotextile
Non-woven geotextile for filtration & separation
Polyfelt TS is a non-woven polypropylene geotextile for filtration, separation and protection over drainage layers, available in graded ranges by mass. Specify the TS grade for the filtration and protection duty with Geofabrics.
Global Synthetics
Global Synthetics Non-Woven Geotextile
Non-woven geotextile for filter & separation duties
Global Synthetics supplies non-woven needle-punched geotextiles for filtration, separation and drainage protection across civil and landscape applications, in graded ranges by mass. Specify the grade for the duty with Global Synthetics.
Elmich
Elmich Filter Fabric
Non-woven filter fabric for VersiDrain / VersiCell build-ups
Elmich filter fabric is a non-woven geotextile used as the filter layer over Elmich VersiDrain / VersiCell drainage cells in green-roof and podium build-ups, keeping growing medium out of the drainage void. Confirm the fabric specification to match the drainage cell and growing medium.
Atlantis
Atlantis Geotextile Filter Fabric
Non-woven filter fabric for Flo-Cell build-ups
Atlantis supplies non-woven geotextile filter fabric used as the filter layer over Flo-Cell drainage cells in podium and planter build-ups, separating the soil / growing medium from the drainage void. Confirm the fabric specification to match the Flo-Cell and the soil.
System Comparison
Filter fabric systems — confirm all selections against the current manufacturer TDS before specifying.
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FILTER FABRIC WITHOUT A FULL PERIMETER WALL LAP WILL FAIL — SOIL BYPASSES THE FABRIC AT THE EDGES
Filter fabric placed flat across the floor of a planter box without lapping up the walls will be bypassed by soil at every edge — fine particles migrate around the perimeter of the fabric and into the drainage cell void below. This progressive edge bypass defeats the entire purpose of the filter fabric, clogging the drainage void from the perimeter inward over time. Filter fabric must be lapped up all four planter walls to a minimum height of 150mm above the top of the drainage cell layer. Secure the fabric to the wall at the top of the lap with tape, staples, or mechanical fixings before growing medium is placed — once growing medium is placed against an unsecured lap, the lap cannot be corrected without removing the growing medium.
DO NOT USE WOVEN GEOTEXTILE AS FILTER FABRIC IN PLANTER BOX OR GROWING MEDIUM APPLICATIONS
Woven geotextiles have a regular grid aperture that progressively blinds under the fine particle load of growing medium, potting mix, and soil — fine particles become lodged in the regular openings and seal the fabric over time, eliminating drainage function. Non-woven needle-punched geotextiles have a randomised three-dimensional fibre structure that resists blinding under fine particle loading. All filter fabric specified above drainage cells in planter boxes and roof gardens must be non-woven. Do not substitute woven geotextile — shade cloth, landscape fabric, or similar products — for non-woven geotextile filter fabric in drainage cell applications.
ADJACENT ROLLS MUST OVERLAP MINIMUM 300MM — BUTT JOINTS ALLOW SOIL BYPASS
Where two adjacent rolls of filter fabric meet, the rolls must overlap by a minimum of 300mm — not butt-jointed edge to edge. A butt joint between two rolls creates an unsealed line gap through which fine particles can migrate from the growing medium directly into the drainage void below. Overlapping rolls by 300mm ensures that fine particles cannot find a path through the lap regardless of how the fabric settles under the growing medium weight. Mark the 300mm overlap line on the first roll before placing the second roll — do not rely on visual estimation to achieve the required overlap.
FILTER FABRIC IS THE FINAL LAYER BEFORE GROWING MEDIUM — CONFIRM THE FULL DRAINAGE SYSTEM IS COMPLETE BEFORE PLACING FABRIC
Filter fabric is the last installed component before growing medium is placed. Once the filter fabric is in position and growing medium is placed above it, all layers below — drainage cells, protection board, and waterproofing membrane — are permanently inaccessible without full removal of the growing medium and fabric. Confirm that the waterproofing membrane has been flood-tested and passed, the drainage cells are correctly positioned and cover the full floor area, the drainage outlets are correctly installed and unobstructed, and the filter fabric is correctly lapped at all walls before growing medium placement commences. Do not place growing medium over filter fabric until every lower layer has been inspected and confirmed correct.
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer technical data sheet, project specification, growing medium particle size distribution, hydraulic design flow rate, loading conditions, GSM requirements, landscape architect specification, and NCC requirements. Filter fabric must be non-woven — not woven. Filter fabric must be lapped up all planter walls minimum 150mm above the drainage cell layer. Adjacent rolls must overlap minimum 300mm. Once growing medium is placed, all layers below the filter fabric are permanently inaccessible. Do not rely on this reference as a substitute for professional hydraulic engineer, landscape architect, or waterproofing consultant advice.