About Fosroc Proofex Sheetdrain

Fosroc Proofex Sheetdrain is a geocomposite drainage and protection membrane engineered to manage groundwater around buried concrete structures. It is built from a high-density polyethylene (HDPE) sheet that is thermoformed into a single layer of cusps (dimples), creating an open three-dimensional void between the cusps. A heat-bonded non-woven polypropylene geotextile is laminated to the cusp tips. The geotextile acts as a filter that lets water and gas pass into the void while holding back soil fines that would otherwise clog the drainage path, and the HDPE core conveys that water down to a perimeter subsoil drain connected to the site drainage system.

The range comes in two thicknesses for two duty levels. Proofex Sheetdrain 80 has an 8mm core and is specified for retained depths up to 6m; Proofex Sheetdrain 100 has a 10mm core, a much higher compressive strength, and is specified for depths up to 20m. In both cases the principle is the same: instead of relying on a 300-500mm thick layer of graded stone behind a wall to drain it, a thin manufactured sheet does the same job in a fraction of the space, with predictable, factory-controlled flow performance.

For Indian projects this product sits firmly in the below-ground waterproofing system rather than replacing it. In a typical Delhi NCR basement or a coastal Mumbai podium, Proofex Sheetdrain is installed over a barrier waterproofing membrane (for example a Proofex sheet membrane or a sprayed/torch-applied system) before backfilling. It performs two jobs at once: it shields that membrane from puncture by angular backfill and shuttering debris, and it depressurises the water table by giving water an easy downward path to the land drain. Space Arc Engineering supplies Proofex Sheetdrain as an authorised Fosroc distributor across Delhi NCR and Pan-India, alongside the compatible Proofex membranes, fixings and detail strips needed to build a complete, warrantable below-ground package.

The technical insight

The product’s value lies in the distinction between waterproofing and drainage. A waterproofing membrane resists water; a drainage composite removes the water pressure that would otherwise test that membrane. By maintaining an air gap of 8-10mm against the wall, Proofex Sheetdrain converts a saturated, full-head condition into a drained condition, so the structure and its membrane see far less hydrostatic load. The two ratings are not interchangeable marketing tiers: compressive strength jumps from 200 KN/m2 (Sheetdrain 80) to 550 KN/m2 (Sheetdrain 100) because at 20m of retained soil the cusps must resist the overburden and remain open for decades. If the cusps crush, the drainage void closes and the product fails silently. Flow capacity to EN ISO 12958 is similarly tiered (1.65 vs 3.5 L/m/s under 20kPa), reflecting both the deeper core and the higher loads of the 100 grade. The geotextile is the other critical element: at 100/85 L/m2/s permeability (EN ISO 11058) it must out-pass the soil while filtering it, which is why Fosroc explicitly excludes very fine uniformly-graded silts, peat, and soils rich in iron oxides/hydroxides where ochre fouling can blind the filter over time.

Where it is used

• Drained protection layer over below-ground waterproofing on basement retaining walls in Type A (barrier) and Type B (structurally integral) systems to BS 8102:2009
• Buried walls of lift pits, service ducts, subways and underpasses where a drainage plane relieves water pressure
• Protection of a sheet or liquid waterproofing membrane against puncture during backfilling operations
• Lost-shuttering drainage liner against directly-cast concrete sub-structure walls that must be drained
• Filtered drainage and protection beneath landscaped podia, plaza decks and elevated slabs
• Roof gardens and earth-covered (green) roofs as a sub-surface drainage and root-protection void
• Drainage behind reservoir and water-retaining structure walls used with Proofex sheet membranes

Key advantages

• Eliminates the up-to-500mm thick graded-stone French drain behind retaining walls, saving excavation width and cost
• High flow rate for both water and gas, reducing hydrostatic and gas pressure against the structure
• Factory-controlled drainage performance to EN ISO 12958, unlike variable site-graded stone
• Doubles as physical protection for the waterproofing membrane during backfill, removing a separate protection board
• HDPE cuspated core with up to 550 KN/m2 compressive strength keeps the drainage void open under long-term backfill loading
• Lightweight rolls (approx 24-25kg) that two operatives can handle, with fast mechanical fixing and simple lapped joints
• Lower environmental impact: no lorry movements to remove spoil and import stone
• CE marked to EN 13252 and chemically resistant to substances found in normal soil conditions

Limitations & considerations

• Not a waterproofing membrane on its own; it manages water but does not stop it, and must work with a dedicated barrier/integral system
• Not recommended in saturated clays beyond 20m (10mm) or 6m (8mm) depth due to long-term loading effects
• Should not be used in soils with high iron oxide/hydroxide content (ochre fouling risk) or in extremely fine uniformly-graded silts or peat
• Drainage performance depends on a functioning, connected perimeter subsoil drain and outfall; without an outlet it cannot relieve pressure
• Backfill must be free of rocks or boulders larger than 50mm and placed in 300mm layers compacted to 85% modified Proctor to avoid cusp damage
• Geotextile orientation matters: it must face the soil and be laid in the direction of flow, or fines can enter and blind the void
• Must not be exposed to direct UV radiation for more than two months in storage before installation
• Some chemicals at certain concentrations can impair drainage; Fosroc technical advice is required for aggressive ground conditions

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Proofex Sheetdrain

Within the Fosroc below-ground portfolio, Proofex Sheetdrain is the drainage-and-protection layer that complements rather than competes with the Proofex tanking membranes (such as Proofex Engage and Proofex sheet membranes) and is fixed using Proofex Detail Strip; for crack-prone construction joints it is often paired with hydrophilic strips or Supercast waterstops on the same structure. It is best understood as Fosroc’s manufactured alternative to a graded-stone French drain and to a plain protection board. Against the wider Indian market, its closest equivalents are dedicated cuspated drainage composites such as Sika’s drainage boards, the geocomposite drainage membranes from STP Limited, and MBS/Dr. Fixit protection-and-drainage boards; specifiers also compare it with imported brands like Delta-MS/Newton (Koster) cavity drainage systems. The honest distinction is that Proofex Sheetdrain is a true two-grade engineered geocomposite with published EN ISO flow, puncture and compressive data and CE certification to EN 13252, which makes it straightforward to specify by depth (6m vs 20m) and to integrate into a single-source Proofex warranty package. Where a project only needs a thin protection board with no real drainage duty, a cheaper plain dimple board may suffice; where the design must demonstrably relieve hydrostatic pressure to BS 8102:2009 at depth, Sheetdrain 100’s 550 KN/m2 core and verified flow capacity are the differentiators. Space Arc Engineering supplies it with the matching Proofex membranes, fixings and technical support across Delhi NCR and Pan-India.

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