Design Width
12–25 mm
Function
Separates two different elements (e.g., slab–column)
Material
Neoprene sheet + PU sealant
Movement
Differential
Typical Application Detail
Between dissimilar materials
Typical Locations
Around columns, ramps, machine bases
Waterproofing Approach
Compressible filler + PU sealant edge
1. Introduction
Isolation joints separate two dissimilar materials or structural elements (e.g., column–slab, wall–floor) to prevent stress transfer due to differential movement.
These joints are critical for avoiding cracks and leakage at structural interfaces.

2. Typical Failures
- Missing compressible filler board.
- No edge sealant leading to seepage.
- Debonding between concrete and sealant.
- Inadequate gap width or poor compaction.
3. System Requirements
- Provide physical separation with compressible filler.
- Apply waterproof edge sealant to prevent ingress.
- Maintain flexibility and continuity with adjacent systems.
4. Recommended Systems
Joint Width | System | Material |
10–35 mm | Filler board + PU sealant | Bitumen-impregnated board / Neoprene |
5. Methodology
- Install compressible filler before casting concrete.
- Trim flush after de-shuttering.
- Apply primer and PU sealant over top edge.
- Provide watertight continuity with waterproofing system.
6. Performance Parameters
Property | Requirement | Standard |
Movement capability | ±25% | ASTM C719 |
Adhesion | ≥1.0 N/mm | ASTM C794 |
Compression recovery | ≥90% | ASTM D3575 |
7. QA/QC Checklist
- ☑ Correct filler type and thickness
- ☑ Flush edge finish
- ☑ Sealant cured
- ☑ No visible gaps or discontinuities
Video Masterclass
Masterclass: Raft Waterproofing – Choosing the Right Technology → Coming Soon
