Protecting buried basement walls against permanent moisture without the hydrostatic pressure of the ground water degrading the waterproofing over time, shielding retaining walls against mechanical damage during backfilling with earth and stones, and creating a ventilation chamber for breathable walls, requires a dimpled HDPE drainage membrane with calibrated dimples and compressive strength for buried use. This dimpled drainage membrane —also called a dimple sheet, or studded membrane— is manufactured by MOLTEXO in 700 g/m² HDPE, in 2×20 m rolls, designed for buried walls, foundations, basements, tunnels and civil construction projects with problems of capillary moisture or groundwater.
Key benefits
- Air gap between wall and ground: the dimples create a circulation space between the wall and the backfill, where infiltrated water flows freely to the lower drainage without putting pressure on the structure, eliminating the hydrostatic pressure that ruins traditional walls.
- Mechanical protection of the waterproofing: the smooth outer face absorbs impacts from stones and compaction of the backfill, preventing damage to asphalt paint, bituminous felt or chemical waterproofing, which, with mechanical damage, loses its watertightness and allows permanent moisture to enter.
- Inert and durable HDPE: polyethylene is chemically resistant to moisture, biological attack (fungi, bacteria), soil alkalis and acids, plant roots and rodents, conditions for decades of service life when buried.
- Wall ventilation against capillary moisture: the air gap allows the wall to breathe and eliminate moisture accumulated by rising capillary action, a critical condition for basements in areas with high water tables in the Caribbean where capillary moisture is a chronic problem.
- Water reserve in green roofs and planters: the "cups" formed by the dimples retain small amounts of water available for the upper substrate between waterings, an additional technical advantage when the membrane is used as a combined drainage-retention layer in green roofs.
Typical applications and uses
- Buried basement walls, stair walls and retaining walls with permanent ground moisture.
- Deep foundations, footings and retaining walls in hydraulic works with hydrostatic pressure.
- Tunnels, underground works and service galleries with perimeter drainage.
- Green roofs and planters with a dual drainage-water retention function for the upper substrate.
Quality and durability
An economical drainage membrane fails in two points: the HDPE is low-grade recycled (which produces dimples that flatten under the weight of the backfill and lose the drainage air gap) and the actual grammage is lower than declared (which produces a thin membrane that tears during backfilling with stones). MOLTEXO works with verifiable virgin 700 g/m² HDPE, which separates a professional construction drainage membrane from a decorative membrane that fails after a few years under the buried wall.
The dimples (studs) face the wall or the waterproofing layer, not the soil. This orientation creates the air gap between wall and membrane, the space where infiltrating water flows freely down to the drainage system at the base without putting pressure on the wall. If the orientation is reversed (dimples toward the soil), the membrane sits flush against the wall with no gap and loses its essential function. The smooth outer face stays in contact with the backfill soil and acts as a mechanical barrier. Always verify orientation before starting fixing.
No. The dimpled drainage membrane is complementary to waterproofing, not a replacement. Its role is to protect the waterproofing layer (bituminous paint, asphalt sheet, water-repellent mortar) against mechanical damage during backfilling and to relieve hydrostatic pressure from groundwater. The wall must already be waterproofed by chemical system before the membrane is installed. The combination of bituminous paint + drainage membrane + base drainage is the professional standard for basements and buried walls; just one of the three does not solve the problem of permanent moisture.
Yes. In planters and green roofs (planted roof systems) it serves a double role: it protects the waterproofing layer of the roof or planter against plant roots and impacts during backfilling with substrate; and the \
High compressive strength thanks to its 700 g/m² HDPE construction with calibrated dimples. The dimpled structure spreads the weight of soil and gravel backfill over the full set of contact points, preventing point crushing and keeping the air gap intact for decades. For greater depths (basements, buried walls several meters tall, green roofs with heavy substrate) the specific load capacity should be verified against the project design. The strength holds up for decades when buried, an auditable condition for the declared service life of the drainage system.
Three complementary accessories that are essential. Top edge profiles in metal or plastic that close the upper zone between membrane and wall, preventing soil and rainwater from entering from above. Mechanical fasteners with steel nails or screws combined with washers or sealing buttons that seal the perforation point and prevent leaks through the hole. A drainage pipe at the base of the membrane (perforated, surrounded by gravel and geotextile) to carry collected water to a drain or pumping pit. Without these three accessories the membrane partially loses its function and the system fails in the medium term.
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| Material | High-density polyethylene (HDPE) |
|---|---|
| Weight per area (specification) | 700 g/m² (20.65 oz/yd²) |
| Sheet height with embossing (dimple) | 8 mm (0.315 in) |
| Tensile force at 10% elongation | ≥350 N/100mm (≥240 lb/ft) |
| Maximum tensile force | 600 N/100mm (≥411 lb/ft) |
| Elongation at break | 25 % |
| Tear strength | 100 N (≥22.5 lbf) |
| Compressive strength | 100 kPa (≥14.5 psi) |
| Appearance after 50% compression | No damage |
| Thermal aging 80°C, 168 h — compressive strength retention | ≥80 % |
| Drainage area (cross-section) | ≥30 cm² (≥4.65 in²) |
| Thermal aging 80°C, 168 h — elongation at break retention | ≥70 % |
| Alkali resistance — compressive strength retention | ≥80 % |
| Alkali resistance — elongation at break retention | ≥80 % |
| UV protection | Yes (high) |
| Roll: Width | 27.0 cm (10.63 in) |
|---|---|
| Roll: Height | 42.0 cm (16.54 in) |
| Roll: Depth | 200.0 cm (78.74 in) |
| Roll: Weight | 28.0 kg |
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