- At a glance
- 1. Introduction
- 2. Why Are Joints Required?
- 3. Types of Joints in Concrete
- 4. Special Case: Injection & Joint Leakage
- Sealants & Tapes
- Selection Matrix
- Disclaimer
How to use this page
- Use the table of contents to jump to joint types, selection matrices, and detailing notes.
- Start with the Selection Matrix to shortlist solutions by movement and exposure.
- Review rules on backer rods, bond‑breakers, and width:depth before finalizing specs.
At a glance
- Joint types: movement, construction, contraction, expansion, isolation
- Solutions: elastomeric sealants, preformed tapes/bands, waterstops, injection grouts
- Key rules: avoid three‑side adhesion, maintain width:depth ≈ 2:1 for joints > 10 mm, use backer rod or bond‑breaker
- Critical checks: substrate dryness, primer compatibility, movement class, shore hardness, service temperature
How to use this hub
- Browse by joint type in the left column.
- Open a sealant card to view the full spec page.
- Use the Selection Matrix to match joint conditions with the right system.
1. Introduction
Concrete joints are created to control movement, prevent cracks, and ensure watertightness when structures expand, shrink, or move due to temperature, drying, or loading conditions. They are intentional weak planes or separations that absorb thermal, structural, or shrinkage stresses, preventing random cracking.
2. Why Are Joints Required?
- Concrete is not ductile — it cannot stretch or bend without cracking.
- It shrinks and expands with moisture and temperature changes.
- When restrained by another structure, these movements cause tensile stresses and cracks. Hence, joints are needed to relieve these stresses and maintain structural integrity.
3. Types of Joints in Concrete
4. Special Case: Injection & Joint Leakage
Injection & Joint Leakage
- Inject low‑viscosity polyurethane (PU) grout — see Injection Grouting Technology — for moving or running leaks.
- Use hydrophilic PU foam where active water flow exists — details in Injection Grouting Technology.
- Inject vinyl acrylate grout for micro‑porosity and damp areas — methodology in Injection Grouting Technology.
This forms a watertight barrier behind the joint.
Sealants & Tapes
Selection Matrix
Disclaimer
Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.