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Aug. 03, 2026
RDP is the most expensive additive in ETICS. Choose wrong and you pay twice — once in money, once in performance. This guide gives you the real test data, so you choose right the first time.
Quick Answers
| Question | Short Answer |
| Which RDP has the best bond and impact? | EVA. But it absorbs too much water |
| Why can't I use EVA alone? | Water absorption hits 900–1000 g/m², way over the 500 limit |
| Why can't I use hydrophobic RDP alone? | It resists water but fails the impact test (2–3 J) |
| What is the industry answer? | EVA + silane powder. Best of both |
| How much RDP do I need? | 2–2.5% standard, 3–3.5% reinforced |
1. The Four Options
In an ETICS base coat, four RDP approaches are common. Tested under the same standard formula (28% cement, 0.2% HPMC, 3% RDP):
| System | What it is | Verdict |
| A. EVA only | VA/E copolymer, 3% | Best bond + impact. Water problem |
| B. EVA + silane | EVA 2.5% + silane 0.3% | Best balance |
| C. VA-VeoVa | VA/VeoVa copolymer, 3% | Moderate, expensive |
| D. Hydrophobic RDP | Hydrophobic VA/E, 3% | Water-resistant but weak |
2. The Three Tests That Matter
Bond to EPS board
| System | Dry (14d) | Wet (14d+2d water) |
| A. EVA | 0.14–0.16 MPa | 0.10–0.12 MPa |
| B. EVA + silane | 0.13–0.15 MPa | 0.10–0.11 MPa |
| C. VA-VeoVa | 0.10–0.12 MPa | 0.07–0.09 MPa |
| D. Hydrophobic | 0.08–0.10 MPa | 0.06–0.08 MPa |
Requirement: ≥0.10 MPa. System D barely passes dry and fails wet.
Impact resistance
| System | Impact | Meets standard? |
| A. EVA | 10–12 J | Exceeds reinforced (≥10 J) |
| B. EVA + silane | 8–10 J | Standard, near reinforced |
| C. VA-VeoVa | 3–4 J | Barely standard |
| D. Hydrophobic | 2–3 J | FAIL (below 3 J) |
Water absorption (24 h)
| System | Absorption | Meets standard? |
| B. EVA + silane | 200–400 g/m² | Yes |
| D. Hydrophobic | 300–500 g/m² | Borderline |
| C. VA-VeoVa | 600–800 g/m² | No |
| A. EVA | 900–1000 g/m² | No (far over) |
3. The Dilemma, in One Picture
EVA gives the best bond and impact, but absorbs 900–1000 g/m² of water.
Hydrophobic RDP resists water, but fails the impact test.
Neither one works alone. That is the trap most formulators fall into.
4. The Answer: EVA + Silane
Add a small dose of silane powder to EVA, and you get both:
| Property | EVA only | EVA + silane |
| EPS bond (dry) | 0.14–0.16 MPa | 0.13–0.15 MPa |
| Impact | 10–12 J | 8–10 J |
| Water absorption | 900–1000 g/m² | 200–400 g/m² |
The silane (0.2–0.3%) cuts water absorption by 60–80% — without hurting the bond or impact much. EVA forms the tough, flexible film. Silane blocks the water.
This is the industry standard choice, and it is what CHARING recommends: RD 7015H (EVA) + a silane hydrophobic powder.
5. How Much RDP? Dosage vs Impact
| EVA RDP dosage | Impact |
| 1% | 2–3 J (fails) |
| 2% | 5–6 J (standard) |
| 3% | 10–12 J (reinforced) |
| 4% | 13–15 J (premium) |
Standard grade: 2.0–2.5% (20–25 kg/t)
Reinforced (ground floor, public areas): 3.0–3.5% (30–35 kg/t)
Premium (schools, hospitals): 3.5–4.0% (35–40 kg/t)
Going from 2% to 3% roughly doubles impact resistance. The extra cost is small next to a failed impact test on site.
6. The Mistakes to Avoid
1. EVA alone. Great bond, but the base coat absorbs 900 g/m² of water. It fails the water requirement and the facade will not last.
2. Hydrophobic RDP alone. It resists water but fails the impact test. Never use it as the only polymer in a base coat.
3. VA-VeoVa for everything. It costs more and gives less. Only worth it where UV and weather resistance are the top priority.
4. Cutting RDP to save money. From 3% to 1.5% halves impact resistance. The system passes a visual check, then fails the first hailstorm.
7. CHARING Recommendation
| Role | Product |
| Base polymer (EVA) | RD 7015H |
| Water resistance (silane) | CHARING Hydrophobic Powder, 2–3 kg/t |
| Hot climate (HPMC) | HK 100M / HK 200M |
Note: The test data above comes from international industry research, not CHARING's own lab. Use it as a reference, then test in your own system with your own cement and sand.
For technical inquiries: info@sdcharing.com
Shandong Charing Industry Co., Ltd.
E-mail: sdcharing@sdcharing.com
Phone: +86 131 7667 0070
WhatsApp: +8615066133527
Add.: No.605-606,NO1 BUILDING,WANGYUE ZHIGU INDUSTRY PARK,NO.1919 WANGYUE ROAD, SHIZHONG AREA,JINAN CITY, SHANDONG PROVINCE,CHINA
