Cementitious and crystalline waterproofing systems sold in India are built around integral waterproofing compounds certified to IS 2645:2003, which BIS licenses separately by powder or liquid form. Around a floor trap, WC outlet or any pipe penetration — the actual failure point in most bathroom and sunken-slab jobs — the plumbing itself carries its own certification: IS 4985:2021 for UPVC water-supply pipe and the IS 2556 series for the sanitary fixture. On GST, cement — the base material in cementitious waterproofing — was cut from 28% to 18% in the September 2025 reform, but no cut has been confirmed for the waterproofing compound, membrane or crystalline product itself.
The compound standard behind cementitious and crystalline systems
BIS's current standard for integral waterproofing compounds used in cement mortar and concrete is IS 2645:2003, licensed under Scheme-I of the BIS (Conformity Assessment) Regulations, 2018 — the same certification framework BIS runs across construction materials. The standard treats powder-form and liquid-form compounds as distinct products: "waterproofing compound of each Type ... shall be tested separately to cover the tested type in the scope of licence," so a manufacturer's licence for the powder version does not automatically cover their liquid version, and vice versa. Ask your contractor which form and which licence number the compound they are using is certified under; a compound described only by brand name ("Dr. Fixit," "SikaTop") without a form and licence number is not a checkable specification.
This is a certification and testing-procedure standard, not a price list — it does not set or imply a rupee figure, so it cannot be used to check whether a quote is fair. What it does let you check is whether the compound in your contract is a real, licensable product category at all.
Where waterproofing actually fails — the plumbing penetrations
A bathroom or sunken-slab waterproofing job is rarely undone by the flat field of the membrane; it fails at the points where a pipe or fixture passes through it. The inlet and outlet pipework embedded in that area is typically UPVC pipe to IS 4985:2021, BIS's current standard for unplasticized PVC pipe for water supply, also licensed under Scheme-I. The fixture that the floor trap or WC pan connects into carries its own certification under the IS 2556 series — BIS confirms at least a dozen active parts of this vitreous-china sanitaryware standard, covering WC pans, squatting pans, wash basins, urinals and bidets separately, each a distinct licensable product.
| Component | Standard to request | Why it matters here |
|---|---|---|
| Waterproofing compound | IS 2645:2003 (state powder or liquid form) | Each form is tested and licensed separately |
| Inlet/outlet water pipe | IS 4985:2021 (UPVC) | The pipe embedded in the treated area is a separate certified product from the membrane around it |
| Floor trap / WC pan fixture | Relevant part of the IS 2556 series | Fixture-to-slab junction is the highest-risk penetration point for a leak |
All three are BIS product manuals administered under Scheme-I of the BIS (Conformity Assessment) Regulations, 2018 — none states a price.
In practice this means asking for the pipe collar or sleeve detail at every penetration in writing — how the waterproofing membrane is dressed up and sealed against the pipe or fixture body — rather than accepting "waterproofing done" as a single line item that assumes the flat field alone.
Sunken slab and terrace treat the same compound differently
A sunken bathroom slab and an open terrace both use compounds certified under IS 2645, but the detailing differs because the failure mode differs. On a sunken slab, the compound sits below the final floor level, sealed in before the fill and the floor trap and WC pan (their own IS 2556-series fixtures) are set in place — once tiled over, any defect can only be found by demolition, which is why the powder-or-liquid licence check matters more here than anywhere else in the flat. On a terrace, the compound sits on top of the slab, exposed to direct sun and monsoon cycling, and can at least be visually inspected and recoated without demolition if it fails early.
This is also why the pipe standard matters twice on a sunken slab: the UPVC inlet/outlet pipe to IS 4985 is embedded in the same pour as the waterproofing compound, so a pipe joint that leaks during the concealed phase saturates the waterproofing from below — a failure mode a terrace, with no embedded plumbing, does not share.
GST: the cement cut does not automatically extend to the compound
The September 2025 GST reform, running under Notification No. 9/2025-Central Tax (Rate), dated 17 September 2025 and confirmed by the Department of Consumer Affairs' FAQ to supersede Notification No. 1/2017-Central Tax (Rate), cut Portland cement from 28% to 18% according to the official PIB rate-change annexure. Because cementitious waterproofing compound is a separate product classification from plain cement, this cut does not automatically transfer to the compound itself — the annexure was searched and no waterproofing-compound, membrane or bituminous-product line item was found among the confirmed changes. Cement used to mix a screed or a cementitious coat may be 18% on the cement component, while the branded compound itself may or may not carry a different rate that this registry could not confirm — ask the contractor to itemise cement and compound separately on the invoice if you want to see each rate.
A second published Consumer Affairs FAQ on the same reform confirms the pattern was selective rather than blanket: most bricks kept their existing composition-scheme rate unchanged (6% without input tax credit, 12% with it), with only sand-lime bricks cut, from 12% to 5%. The same selectivity is the safest working assumption for any specific waterproofing material until its own rate is separately confirmed.
What this registry could not verify for waterproofing specifically
The National Building Code of India is the natural authority for a waterproofing-detailing clause — parapet upturn height, slope-to-drain requirements, membrane lap widths — but its current 2016 edition (NBC 2016) is a paid, multi-volume BIS publication and its live scope page did not surface fetchable clause text in this pass. Bureau of Indian Standards is named here as the authority a reader should check directly for any specific NBC clause on waterproofing detailing; no clause number or requirement text from NBC 2016 is stated on this page because none could be independently verified.
Similarly, no numeric water-absorption percentage or performance threshold for the IS 2645 compound itself was captured in this pass — the product manual confirms the certification scheme and the powder/liquid distinction, not the pass/fail numbers a lab test would report.
Methodology
Standard numbers and certification-scheme mechanics are taken from the IS 2645:2003, IS 4985:2021 and IS 2556 (Part 2):2024 BIS product manuals, none of which state a price. The cement GST rate is taken from the official 56th GST Council annexure; the absence of a confirmed rate for waterproofing compound specifically reflects a full-text search of that same annexure finding no matching line item, cross-checked against notification numbers and the brick composition-scheme mechanics in two Department of Consumer Affairs FAQs.
Sources
- Bureau of Indian Standards — Product Manual, IS 2645:2003, Integral Waterproofing Compounds — accessed 2026-09-21
- Bureau of Indian Standards — Product Manual, IS 4985:2021, Unplasticized PVC Pipes for Water Supplies — accessed 2026-09-21
- Bureau of Indian Standards — Product Manual, IS 2556 (Part 2):2024, Vitreous China Sanitary Appliances — Washdown Water Closets — accessed 2026-09-21
- Press Information Bureau — Recommendations of the 56th GST Council Meeting — accessed 2026-09-21
- Department of Consumer Affairs — Frequently Asked Questions – 3 (GST rate rationalisation, Sept 2025) — accessed 2026-09-21
- Department of Consumer Affairs — Frequently Asked Questions – 2 (GST rate rationalisation, Sept 2025) — accessed 2026-09-21