1. Inspect Product Labeling and Packaging
High-quality products have clear packaging with the following information: manufacturer's name, address, contact information, product model (e.g., K11, JS, polyurethane), executive standards (e.g., GB/T 23445-2009 Polymer Cement Waterproof Coatings, GB/T 19250-2013 Polyurethane Waterproof Coatings), production date, shelf life, and net weight.
Inferior products often lack clear models or executive standards (e.g., only labeled "waterproof coating" without specific categories), contain typos, or use shoddy packaging materials that are easily damaged.
2. Request "Two Reports": Test Report + Factory Qualification Certificate
Ask the supplier for a third-party authoritative test report (valid within the past 1–2 years, not expired). Focus on key performance indicators in the report:
| Core Test Item | High-Quality Standard (Taking Common K11 Waterproof Coatings as an Example) | Issues with Inferior Products |
|---|---|---|
| Water Resistance (7 days) | No blistering, no peeling; tensile strength retention rate ≥ 80% | Peeling, cracking, sharp drop in strength |
| Tensile Strength | ≥1.8MPa (Type I), ≥1.5MPa (Type II) | Below standard, easy to break |
| Elongation at Break | ≥300% (Type I), ≥200% (Type II) | ＜100%, easy to crack after film formation |
| Water Impermeability (0.3MPa, 30min) | No water seepage | Water seepage within 30 minutes |
The factory qualification certificate must be stamped with the manufacturer's official seal and marked "Qualified". Products without a certificate or only with a handwritten "Qualified" label should be avoided.
3. Identify Brand and Reputation
Prioritize brands with recognition and stable market reputation (e.g., Oriental Yuhong, Davco, Keshun). These brands have standardized production processes and reliable after-sales support.
Avoid "three-no small-factory products" (no brand, no manufacturer, no standards). Such products are mostly "workshop-style production" using inferior raw materials (e.g., waste engine oil, low-quality resin). Their waterproof effect only lasts 3–6 months, and leakage is likely to occur.
II. Second, Conduct "Visual Judgment": Preliminary Screening Through Sensory Experience
No professional tools are needed-you can quickly eliminate obviously inferior products through "visual inspection, smell test, and touch check":
1. Visual Inspection: Observe Appearance and State
Liquid coatings (e.g., JS, polyurethane): High-quality products are uniform without stratification, sedimentation, or caking (slight stratification is normal and can be restored to uniformity after stirring). Inferior products show obvious "oil-water separation" (e.g., oil floating on top of polyurethane coatings, caking at the bottom) or contain impurity particles.
Paste/powder coatings (e.g., cement-based capillary crystalline coatings): High-quality products have uniform color and fine powder without coarse particles; after mixing with water, there are no "lumps". Inferior products are easy to cake, and after mixing, there are undissolved hard particles that affect film formation.
2. Smell Test: Be Alert to "Pungent Odors"
High-quality coatings:
Water-based coatings (e.g., JS, K11): Only have a slight "emulsion smell" or "cement smell" without irritating odors.
Solvent-based coatings (e.g., polyurethane): Although they have a certain odor (due to solvents), the smell is "mild and non-irritating" and leaves no residual odor after volatilization.
Inferior coatings: Mostly contain harmful substances such as formaldehyde and benzene. They have a strong, pungent odor (e.g., "paint smell" or "sour smell") that causes dizziness and nausea after inhalation, and long-term exposure is harmful to health.
3. Touch Check: Test Film Formation Effect (Small-Scale Trial Application Recommended)
Apply a small amount of coating to a cement board and wait for it to fully cure (per product instructions, usually 24–48 hours). High-quality coatings will form a film that is smooth and flat, without cracks or bubbles; it has "flexibility" when pressed with fingers (e.g., the film does not break when the cement board is bent), and no obvious scratches are left after being scratched with a fingernail.
Inferior coatings form brittle, crack-prone films that break when pressed; some remain sticky (incomplete curing) and peel off when scratched with a fingernail-their waterproof effect is naturally poor.
III. Key "Performance Testing": Verify Core Waterproof Capability
If conditions permit, simple tests can be conducted to further verify performance (especially for coatings used in critical areas such as bathrooms and roofs):
1. Adhesion Test
After the film is fully cured, use a utility knife to score a "crosshatch pattern" on the film (1mm spacing, deep to the substrate). Stick tape to the crosshatch, then tear it off forcefully:
High-quality coatings: No film peeling off the tape, and the edges of the crosshatch are neat.
Inferior coatings: The film is easily peeled off by the tape, indicating poor adhesion-bubbling and peeling are likely to occur later.
2. Simple Water Resistance Test
Small-scale trial application: Apply 2–3 coats of the coating to a cement board (per standard construction thickness, usually 1.5–2mm). After curing, place the cement board with the "film side up", pour a small amount of water (or place a basin of water), and let it stand for 24 hours:
High-quality coatings: No water seepage or moisture penetration (the reverse side remains dry).
Inferior coatings: The reverse side shows "watermarks" or even direct water seepage.
For roof coatings, an additional "temperature difference simulation" can be done: Freeze the test board in a refrigerator (around -5℃) for 2 hours, then place it at room temperature. Repeat 3 times. High-quality coatings will not crack or seep water, while inferior coatings will crack easily due to poor weather resistance.
IV. Align with "Scenario Requirements": Adaptability Matters More Than "Superior Parameters"
Even the best coating will "malfunction" if it does not match the usage scenario. Choose the right coating type based on the area-this is also a hidden criterion for judging "quality":
| Usage Scenario | Core Requirement | Characteristics of High-Quality Coatings | Inferior Misconception (Wrong Selection = Waste) |
|---|---|---|---|
| Bathrooms/Kitchens | Strong impermeability, good flexibility (to avoid leakage from substrate microcracks) | Choose K11 or JS waterproof coatings; the film has elasticity | Using rigid coatings (e.g., pure cement-based) that crack when the substrate shifts |
| Roofs/Exterior Walls | Strong weather resistance (UV resistance, freeze resistance, anti-aging) | Choose polyurethane or acrylic waterproof coatings; UV and temperature-resistant | Using water-based coatings (e.g., ordinary JS) that age and crack under long-term sun exposure |
| Basements/Water Tanks | Strong water pressure resistance, good crystalline penetration | Choose cement-based capillary crystalline coatings or polymer sheet-matching coatings | Using ordinary coatings with insufficient water pressure resistance that easily leak |
V. Avoid 3 Common "Misconceptions"
Misconception 1: "The thicker, the better"
Coating thickness does not equal performance. Some inferior products add fillers like talc or heavy calcium to increase thickness, but this reduces the film's tensile strength and waterproofness-cracking is more likely.
Misconception 2: "The cheaper, the more cost-effective"
High-quality coatings have higher raw material costs (e.g., high-quality emulsions, imported additives), usually priced at 50–150 RMB per square meter (after construction). Products cheaper than 30 RMB per square meter are likely "cutting corners"-they may not leak in the short term but will fail within 1–2 years, leading to higher repair costs later.
Misconception 3: "Only focus on waterproofness, ignore environmental protection"
Inferior coatings contain large amounts of harmful substances (formaldehyde, VOCs). Even if their waterproof effect meets standards temporarily, they release toxic fumes long-term, affecting indoor air quality. Prioritize "low-VOC" and "formaldehyde-free" products (check the "VOC content" index in test reports-national standards require ≤120g/L).
By following these methods, you can comprehensively judge the quality of waterproof coatings from four dimensions: compliance, sensory experience, core performance, and scenario adaptability. Ultimately, choosing a product with "complete qualifications, no pungent odor, good film formation, and scenario adaptability" ensures long-lasting waterproof effects (high-quality coatings, when applied properly, have a waterproof lifespan of 10–15 years or more).
