Geocomposite wall drain, thin where gravel was thick.
A geocomposite wall drain replaces 200-400 mm of granular drainage aggregate behind retaining walls and bridge abutments with a prefabricated 15-25 mm panel: HDPE three-dimensional cuspated core for in-plane flow, nonwoven PP filter face against the retained soil. Transmissivity (ASTM D4716) sized to the project drainage demand, filter AOS sized to native fines, anchored at the top and gravity-hung against the wall back face. We supply StrataDrain through Starwall (sole STRATA distributor) and install with CIDB G7 wall crew across Klang Valley, Penang, Johor, Pahang, Sabah, and Sarawak. The standard back-of-wall drain on tight urban sites, bridge abutments, basement perimeter, landfill caps, and SRW projects above 3 m height.
HDPE 3D core plus nonwoven filter face.
A geocomposite wall drain is two products bonded into one delivery.
- Drainage core. A three-dimensional HDPE sheet stamped or extruded into a cuspated (egg-crate) or pin-array geometry, typically 5-25 mm overall thickness. The cusps create an open in-plane flow path that carries water parallel to the wall face. Compressive strength of the core is the primary design check (the core has to keep its geometry under the design overburden pressure, typically 50-250 kPa at the bottom of a routine wall).
- Filter face. A nonwoven polypropylene geotextile, typically 100-200 gsm, bonded (laminated or stitched) to one side of the core (single-sided product, for use against a hard wall back face) or to both sides (double-sided product, for use in free-standing drainage applications). The filter face passes water into the core while retaining the native fines on the upstream side.
The product is delivered in rolls (typical 1.0-2.0 m wide, 30-50 m long), rolled out vertically against the wall back face, anchored at the top, and outlet-connected at the bottom. For routine retaining wall and bridge abutment applications, the single-sided product (filter face on retained-soil side, bare core on wall side) is the standard configuration; double-sided is used at landfill cap chimney drains and sub-pavement chimney drains where the drain is sandwiched between two soil layers.
The numbers that drive selection.
| Property | Test method | Specification driver |
|---|---|---|
| In-plane transmissivity (litres per second per metre wall width) | ASTM D4716 / BS EN ISO 12958 | Headline drainage capacity at design overburden and gradient; size against project rainfall plus retained-soil seepage demand. |
| Compressive strength (kPa at maximum design overburden) | ASTM D6364 / BS EN ISO 25619 | Core must retain its geometry under design overburden; typical product range 200-1500 kPa, select to wall height plus surcharge. |
| Filter face mass per unit area (gsm) | EN ISO 9864 | 100-200 gsm typical for back-of-wall; 200-400 gsm for landfill cap (puncture protection above geomembrane). |
| Filter face AOS / O90 (mm) | BS EN ISO 12956 / ASTM D4751 | Size to native soil fines; typical 0.06-0.20 mm for routine MY sandy-clay backfill. |
| Filter face permittivity (per second) | BS EN ISO 11058 / ASTM D4491 | At least 10x the soil permeability; typical 1.0-3.0 per second for back-of-wall filter grades. |
| Core polymer | HDPE per ASTM D1505 density | HDPE is the standard core polymer for permanent drainage applications; chemically stable in neutral Malaysian ground. |
| Roll dimensions (width x length) | Product datasheet | 1.0-2.0 m x 30-50 m typical; matches wall lift heights and minimises horizontal joints. |
| Long-term reduction factors (creep, intrusion, biological) | BS EN ISO 12958 | Design transmissivity typically 30-60 percent of manufacturer headline; apply RF_CR, RF_IN, RF_BC per project context. |
Where it goes across Malaysian projects.
1. RC cantilever and gravity retaining wall
Reinforced concrete cantilever and gravity walls (1.5-6 m typical height) routinely use geocomposite drain behind the wall stem to manage retained-soil seepage and prevent hydrostatic pressure buildup. Replaces the conventional 300 mm gravel drainage blanket with a 20 mm panel; saves back-of-wall excavation width on tight urban sites. Outlet through weep holes at 2-3 m horizontal centres at wall toe or to perimeter perforated pipe.
2. MSE precast panel wall
Tall MSE walls (5-12 m) with concrete panel facing on highway, port, and industrial projects. The geocomposite is placed against the precast panel back face during construction, between the panel and the reinforced fill zone. Standard configuration on JKR highway bridge approach MSE walls and PLUS interchange retaining structures. Outlet to perforated pipe at wall toe, with intermediate outlets every 5 m vertical for walls above 8 m.
3. Segmental retaining wall (SRW) above 3 m
Segmental dry-stacked concrete block walls. Above 3 m, the conventional gravel drainage chimney becomes hard to detail within the block-to-block geometry. Geocomposite drain placed immediately behind the block face provides controlled drainage in a 15-20 mm envelope, allowing the reinforced fill zone behind to be designed without intrusion of a gravel chimney. See our geogrid for retaining wall page for the wall reinforcement detail.
4. Bridge abutment back-of-wall drainage
Highway and rail bridge abutments where access is constrained by the bridge deck above. Geocomposite is rolled vertically against the abutment back face in continuous panels, anchored at the top of the abutment. Particularly valuable on staged construction where the bridge deck is in place before the approach embankment is built; gravel placement under deck is impractical, geocomposite installs cleanly.
5. Basement perimeter wall
Urban building basement walls where back-of-wall excavation is constrained by adjacent property or site boundary. Geocomposite double-sided product is installed against the basement wall waterproofing membrane, providing groundwater drainage to perimeter perforated pipe at the basement slab level. Standard component of urban basement waterproofing scopes alongside the bituminous waterproofing membrane.
6. Landfill cap chimney drain
DOE landfill closure cap profiles use a chimney drain on the cap slope to intercept percolation and convey it to the toe drain. Geocomposite double-sided drain placed in a 25-50 mm slot through the cover soil, anchored at top and toe-connected to the perimeter outlet, provides uniform drainage capacity over the full cap area. Pairs with the landfill liner system at the cap profile.
7. Sub-pavement chimney drain
Highway pavement and airport runway sub-base drainage where the chimney drain replaces a granular drainage blanket below the pavement structure. Geocomposite placed in a vertical slot through the pavement formation, top-connected to the pavement edge drain, manages groundwater intercepts and prevents pavement formation saturation.
8. Tunnel portal and retaining wall toe
Tunnel portal cuts and deep retaining wall toe locations where intercepting seepage at the wall toe is critical. Geocomposite drain placed against the cut face from formation level up to design intercept elevation; collects seepage and directs to perimeter outlet. Particularly used at hillside cuttings and portal approaches.
Total installed cost not unit price.
Geocomposite drain is more expensive per square metre of wall area than graded gravel drainage; on a unit-price basis gravel wins. But total installed cost (material + transport + placement + ancillary works) often favours the geocomposite, especially on the contexts listed below. Send the project brief and we run the comparison.
| Cost element | Graded gravel drainage | Geocomposite drain |
|---|---|---|
| Material unit cost (per m² wall face) | RM 30-60 (gravel + filter geotextile) | RM 60-120 (geocomposite roll, single-sided) |
| Transport to site | Trucks of gravel; 200-400 mm depth = 0.3-0.5 m³ per m² wall | Rolls; less than 0.05 m³ per m² wall |
| Placement labour and plant | Excavator loading, manual placement, compaction in lifts | Crew of 2 unrolls and anchors; no aggregate handling |
| Quality control | Gradation testing per delivery, compaction record per lift | Manufacturer COA per roll; visual inspection at placement |
| Back-of-wall excavation width | Wall plan + 0.3-0.5 m drainage envelope (excavation widens) | Wall plan + 25 mm (effectively the wall plan only) |
| Risk of segregation / compaction loss | Real (gradation drift, oversized cobbles, compaction-induced fines) | None (consistent factory product) |
| Site context that favours this option | Open rural sites with cheap quarry source and generous wall back-of-face envelope | Urban tight sites, bridge abutments, fast-track, tall walls, SRW above 3 m |
The break-even is project-specific but in Malaysian practice the geocomposite usually wins on total installed cost for walls above 4 m height on constrained urban sites, on all bridge abutments, and on all SRW projects above 3 m. See our drainage method comparison for the broader selector.
From roll to outlet, five steps.
- Prepare wall back face. Clean loose material, check for sharp protrusions (rebar ends, formwork tie offcuts) that could puncture the filter face. Verify the wall back face is acceptable for direct geocomposite contact.
- Unroll vertical panels against the wall. Standard rolls (1.0-2.0 m wide, 30-50 m long) are unrolled vertically against the wall back face, filter face oriented toward retained soil, core toward wall. Cut to length at top and bottom.
- Anchor at top. Mechanical anchors (concrete anchors, insulation pins, or proprietary clips per the geocomposite supplier instruction) through the top of the panel into the wall face at 0.3-0.5 m horizontal centres. The geocomposite hangs by gravity once fixed at the top; no continuous fixing required down the wall face.
- Overlap adjacent panels. 100-200 mm overlap between adjacent vertical panels, with the upslope panel filter face overlapping the downslope panel core (so retained-soil fines cannot bypass into the core through the overlap joint). Secure the overlap with adhesive tape or zip ties through the core.
- Connect bottom to outlet. The bottom 0.3-0.5 m of the geocomposite is wrapped into a perforated PVC or HDPE pipe (typical 100-150 mm diameter) inside a small filter-wrapped granular pocket at the wall toe. The pipe connects to positive outlet via wall toe weep holes (2-3 m horizontal centres) or to perimeter perforated pipe at the wall toe drainage trench.
For tall walls (above 8 m) intermediate outlet collection at 5 m vertical intervals reduces vertical head buildup in the drain; intermediate outlets connect to through-wall weep pipes or to intermediate perimeter pipes. For multi-tier walls (terraced walls with intermediate berms), each tier gets its own geocomposite + outlet at the berm level.
BS EN 13252 product, BS 8006 application.
Two reference standards anchor Malaysian geocomposite drain submissions.
- BS EN 13252 (Geosynthetics: characteristics required for use in drainage systems). Product-level conformance standard. Covers in-plane water flow capacity, compressive strength at design overburden, filter face AOS and permittivity, and long-term creep. Manufacturer certificate of conformance per delivery is normally required; we provide it on every StrataDrain roll.
- BS 8006-1 (Code of practice for strengthened/reinforced soils and other fills). Application-level reference for back-of-wall drainage on reinforced soil walls and reinforced soil slopes. Provides the drainage zone sizing approach and outlet detailing requirements.
- AASHTO LRFD bridge design specifications + FHWA-NHI-10-024. Reference for bridge abutment back-of-wall drainage on highway projects (JKR, PLUS, MRT/LRT viaduct abutments).
- JKR specification SPJ/2008/S4 (Earthworks). Provides the working-level Malaysian highway specification for back-of-wall drainage where geocomposite is the specified material; supplier datasheet pinned to the JKR clause.
Site-specific design typically runs a transmissivity demand calculation (project rainfall infiltrating retained backfill plus any in-soil seepage from groundwater, divided by drainage panel width) against the reduced design transmissivity of the geocomposite product (manufacturer value reduced by RF_CR, RF_IN, RF_BC per ASTM D4716 / BS EN ISO 12958). Outlet detailing is sized so the toe drain pipe capacity exceeds the drainage panel discharge.
Drainage + wall scope.
Drainage design reference →
All drainage systems.
Drainage with geocomposite →
Detailed reference.
Compare drainage methods →
Gravel vs geocomposite selector.
Geotextile for drainage →
Filter applications.
Geogrid for retaining wall →
Wall reinforcement.
MSE wall →
Service hub.
Retaining walls →
Sector page.
Landfill liner design →
Cap and base drainage.
Wall drain spec or back-of-wall brief?
WhatsApp the wall cross-section, design height, surcharge, and target drainage zone. Same-day transmissivity sizing, filter-face AOS, anchor / outlet detail, and price from PJ HQ. National coverage including Sabah and Sarawak.