Waterproofing Systems Guide: JS, CCCW, K11, Polymer Mortar — Which One to Use and Why

Quick Answers

1. Waterproofing Classification: Four Systems Under Four Standards

The Chinese market uses four national/industry standards to define waterproofing products. Each standard defines a different material system with different properties and applications.

The Rigid-to-Flexible Spectrum

The rule: Rigid waterproofing bonds well to tiles but cracks under structural movement. Flexible waterproofing absorbs movement but is a poor substrate for tiles. The choice depends on whether you are waterproofing a wall (tiles on top) or a floor (no tiles, or tiles with special preparation).

2. Polymer Waterproof Mortar (JC/T 984)

What Is It?

A single-component dry powder mortar. Mixed with water, applied at 5-8 mm thickness. The most rigid waterproofing system — compressive strength ≥18 MPa, but near-zero elongation.

Why Use It?

This is the standard waterproofing for tiled walls — bathrooms, kitchens, balconies. Because it is cement-based and rigid, tile adhesive bonds to it almost as well as to bare concrete. No screed layer needed.

Formulation

Water: 16-18%

Key Properties

Compressive strength: ≥18 MPa (28 d)

Tensile bond strength: ≥0.8 MPa

Water absorption: ≤6%

No transverse deformation requirement

3. K11 Polymer Waterproof Slurry (JC/T 2090)

What Is It?

A two-component system — powder (cement + sand + additives) mixed with liquid polymer emulsion on site. "K11" was originally a trade name from Davco (德高), but is now used generically across the industry for JC/T 2090 products.

Type I vs Type II

When to Choose K11 over JC/T 984 Mortar

K11 Type I is comparable to JC/T 984 mortar for wall applications. The difference: K11 uses on-site polymer emulsion mixing, which gives slightly better crack-bridging. JC/T 984 is a dry powder — simpler logistics, no liquid component to transport. Formulators choose based on their distribution model and customer preference.

4. JS Waterproof Coating (GB/T 23445)

What Is It?

The most flexible cement-based waterproofing. Two-component: powder (cement + filler) + liquid (polymer emulsion, typically styrene-acrylic or VAE). Applied at 1.5-2.0 mm in 2-3 cross-direction coats.

Type I, II, III — Key Differences

Important: JS-II with 80% elongation is already soft enough that tiles may debond if applied directly. JS-I with 200% elongation is never directly tileable — the membrane deforms under tile weight and thermal movement.

Why Tiles Fail on JS Waterproofing

When flexible waterproofing is applied to a wall and tiles are bonded on top with standard C1 adhesive, three problems occur:

1.The membrane deforms. A 200%-elongation JS-I coating stretches under the tile's weight, creating shear stress at the tile-adhesive interface.

2.The adhesive cannot follow. C1 tile adhesive is semi-rigid. When the substrate flexes 1-2 mm, the adhesive cracks.

3.Water accumulates. Once the adhesive cracks, water enters and the failure accelerates.

The fix: For JS-II or more flexible membranes, apply a 3-5 mm cement mortar screed layer between the waterproofing and the tile adhesive. This creates a rigid, dimensionally stable bridge layer. Alternatively, use C2S1 adhesive with RD 8080F at 30-40 kg/t — this provides enough flexibility to accommodate minor membrane movement.

5. CCCW — Cementitious Capillary Crystalline Waterproofing (GB 18445)

What Is It?

A dry powder containing Portland cement, quartz sand, and active chemicals. When mixed with water and applied to concrete, the active chemicals penetrate into capillary pores and react with calcium hydroxide to form insoluble crystalline complexes. These crystals physically block water passage.

When to Use CCCW

Basement waterproofing (interior/negative side)

Concrete water tanks and reservoirs

Tunnel and underground structure waterproofing

Concrete repair where surface coating is impractical

When NOT to Use CCCW

On brick or block walls — CCCW requires concrete as the substrate

On flexible substrates — it is rigid and will crack

For crack widths >0.4 mm — needs epoxy injection first

On bathroom walls — overkill, use JC/T 984 or K11

The Self-Healing Mechanism

CCCW's defining feature: when a new crack forms (up to 0.4 mm), water entering the crack reactivates the dormant chemicals, triggering new crystal growth that seals the crack. This is why CCCW is specified for structures where access for repair is impossible — it repairs itself.

6. How to Choose Waterproofing by Location

7. Tile Adhesive Selection over Waterproofing

This is the most common failure point in waterproofing systems. The table below maps waterproofing type to required tile adhesive grade.

8. CHARING Products for Waterproofing System

9. Frequently Asked Questions

What is the difference between JS and K11?

JS (GB/T 23445) is a waterproof coating — applied thin, forms a flexible film. K11 (JC/T 2090) is a waterproof slurry — applied thicker, more rigid. JS for floors where flexibility matters. K11 for walls where tile bonding matters.

Can I tile directly over waterproofing?

On rigid waterproofing (JC/T 984, K11 Type I): yes, with C1 adhesive for ceramic, C2 for porcelain. On flexible waterproofing (JS-I, JS-II, K11 Type II): no — apply a 3-5 mm cement screed first, or use C2S1 adhesive.

Which waterproofing is best for a bathroom?

Walls: JC/T 984 polymer waterproof mortar or K11 Type I. Floor: JS Type II. The wall waterproofing must support tiles; the floor waterproofing must be flexible enough to handle thermal changes and minor settlement.

Why did my tiles fall off the bathroom wall?

The most common cause: flexible JS waterproofing was used on the wall under C1 adhesive. The membrane flexes, the adhesive cracks, the tiles fall. For bathroom walls, always use a rigid system (JC/T 984 or K11 Type I).

What thickness should waterproofing be?

JS coating: minimum 1.5 mm dry film (2-3 coats, 0.5-0.8 mm each). Polymer mortar: 5-8 mm. CCCW: slurry coat, approximately 1.0-1.5 kg/m² powder consumption. Too thin and the film is discontinuous; too thick and it cracks during curing.

How long to wait before tiling over waterproofing?

JC/T 984 and K11: 24-48 hours at 20°C, fully cured in 7 days. JS: 24 hours between coats, 3-7 days full cure before tiling. CCCW: keep damp for 7 days, tiling after 14 days. Cold weather (<10°C) doubles all curing times.

What RDP is best for waterproofing?

For rigid systems (JC/T 984): RD 8080F (Tg -8°C) at 15-30 kg/t, or RD W8050 (Tg -11°C, hydrophobic) for enhanced water resistance. For flexible systems (JS): use RD W8050 at 30-50 kg/t. The hydrophobic treatment in RD W8050 prevents the polymer film from softening under prolonged water exposure.

Why does CCCW need wet curing?

The crystalline growth reaction requires water. If CCCW dries out within the first 7 days, the active chemicals never fully react and the waterproofing effect is lost. Keep the surface damp — spray with water 2-3 times daily for 7 days.

Can I use the same waterproofing for interior and exterior walls?

Yes for JC/T 984 — it is inherently weather-resistant. JS coatings (especially Type I with >200% elongation) are not UV-stable and should not be left exposed. If JS is used externally, cover with render or tiles within 7 days.

Note: All waterproofing systems must comply with GB 55030-2022 (General Code for Waterproofing of Buildings and Municipal Engineering), which sets mandatory waterproofing design working life requirements. System selection must consider both the standard for the material and the code for the structure.

For technical inquiries: info@sdcharing.com 

Shandong Charing Industry Co., Ltd. 

www.sdcharing.com