About STP ShaliCem EWP AR

Most terrace waterproofing coatings are engineered to fight water. ShaliCem EWP AR is engineered to fight water and roots together, which is a different problem. Once a terrace, podium deck or planter is handed over for landscaping, the membrane underneath stops dealing with rain alone and starts dealing with continuous soil moisture, fertiliser runoff and root hairs probing every seam for years. STP Limited, the 85-year-old major behind the Shalimar Tar Products legacy and the “Shali” product family, built EWP AR for exactly that scenario: a ready-to-use, two-component cementitious elastomeric coating, formulated from graded cement, admixtures, synthetic resins and polymers, applied with a stiff fibre brush in two coats over a primed, damp substrate.

What sets it apart from a generic elastomeric coating is that STP has actually tested it to ANSI/GHHC/SPRI VR-1, the recognised green-roof industry protocol for root-resistance, and it passed. Add 40% elongation, a 2mm crack-bridging rating, 630 N/5cm tensile strength and a reinforced water head resistance of 30 metres, and you get a membrane that stays intact as the slab moves seasonally and the planting above it grows. It’s also UV resistant, with no remarkable change after 500 hours of exposure — relevant on Delhi NCR terraces that bake in direct sun for months before planting even begins. Specifiers use it as the waterproofing layer beneath soil in terrace gardens and planter boxes, then protect it with a 15-25mm PCC screed wherever the area sees foot traffic or heavy planters.

The technical insight

“Anti-root” gets used loosely in this market, often on coatings that are simply UV-stable or thick enough to slow roots for a season. STP backs the claim with an actual recognised test method: ANSI/GHHC/SPRI VR-1 subjects the cured film to sustained root-growth pressure and checks for penetration — a meaningfully higher bar than a marketing line. The coating’s 1.80 mixed density signals a well-loaded, dense cementitious-polymer film rather than a thin paint-like layer, and that density is exactly what a root tip has to fail against. The trade-off is workability: at 30°C pot life is a strict 1 hour, and Delhi summer site temperatures routinely run hotter, shrinking the window further. Crews that mix a full 20kg kit at once in peak summer often end up discarding stiffened material; small-batch mixing timed to the actual coat-and-cover rate, not calendar convenience, is the fix.

Where it is used

• Terrace gardens and roof gardens over RCC slabs
• Planter boxes and raised beds on podium or parking decks
• Landscaped podium decks in residential townships and gated communities
• Waterproofing beneath the growing medium in green-roof systems
• Balconies, sunshades and utility decks with planting elements
• Basement and podium-level green spaces in commercial complexes
• Nursery and horticulture display beds on structural slabs
• Retrofit of terraces where an earlier, non-tested coating failed to root ingress

Key advantages

• Passed ANSI/GHHC/SPRI VR-1 — a genuine, testable anti-root claim, not a marketing label
• 40% elongation with 2mm crack-bridging over hairline slab movement
• UV resistant, no remarkable change after 500 hours of exposure
• High reinforced water head resistance (30m) suited to planters holding standing water
• Cementitious chemistry bonds to damp concrete — no need for a bone-dry slab
• Simple two-coat brush application, no spray rig required
• Can be over-protected with a 15-25mm PCC screed for trafficable, planted areas
• Backed by STP’s pan-India technical advisory cell and 85+ years of local manufacturing

Limitations & considerations

• Pot life is a tight 1 hour at 30°C, shorter still in peak Indian summer heat
• Needs a damp, not wet or dry, substrate and disciplined moist curing — poor prep is the usual cause of field failure
• The VR-1 pass covers the coating; large planters with aggressive or deep-rooted species still need adequate soil depth or a supplementary root barrier
• Not a structural repair product — cracks and honeycombing need Shalimar Dam-It or PlastiSeal first
• Less elongation headroom than fully elastomeric liquid-applied or PU membranes at high-movement joints
• Roughly 24-hour dry-back plus a 3-day minimum moist cure before soil loading, which compresses fast-track handovers

Selection & best practice

Specifications

Industry use cases

How we position STP ShaliCem EWP AR

Within STP’s own Shali family, EWP AR sits alongside ShaliCem EWP, EWP 150 and EWP 200 (general terrace/roof elastomeric coatings without root-resistance testing) and ShaliCem FWP (a related polymer-modified coating for general concrete protection); the priming step pulls in ShaliCrete E as the bonding-slurry partner, and pre-existing cracks route through Shalimar Dam-It or PlastiSeal before EWP AR goes down. Outside the STP range, where a project wants an integral, self-healing waterproofing system rather than a topical anti-root membrane — say, a podium garden where future digging or replanting is likely — Fosroc’s crystalline Brushbond TGP is a genuine alternative for the same terrace-garden and planter use case, worth weighing case by case rather than defaulting to either brand.

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