What is a Cold Joint? (And How to Avoid It)

What is a Cold Joint? (And How to Avoid It)

A cold joint is a weak seam formed when pouring new concrete against concrete that has already started to set. It creates a weak point in the concrete. Avoid cold joints by pouring continuously. Understanding cold joints helps ensure strong, monolithic concrete.

What is a Cold Joint?

A cold joint is:

• Weak seam: Boundary between two pours
• Different ages: New concrete poured against older concrete
• Weak bond: Poor bonding between pours
• Potential failure point: Weak area in concrete

How Cold Joints Form

Cold joints happen when:

1. First pour starts setting: Concrete begins to harden
2. Pause in pouring: Pouring stops for too long
3. New concrete added: Fresh concrete poured against set concrete
4. Weak seam forms: Poor bond creates weak joint

Why Cold Joints Are Problematic

Cold joints create problems:

• Weak area: Seam is weaker than monolithic concrete
• Potential failure: May crack or fail at joint
• Water penetration: Water can penetrate along joint
• Reduced strength: Overall strength reduced

How to Avoid Cold Joints

Pour continuously to avoid cold joints:

• Plan ahead: Ensure enough concrete and workers
• Pour continuously: Don't stop pouring once started
• Work efficiently: Move quickly but carefully
• Have help ready: Enough workers to complete pour

If You Must Stop

If you must stop:

• Stop at control joint: If possible, stop at planned joint
• Roughen surface: If continuing later, roughen first pour
• Use bonding agent: Apply bonding agent before continuing
• Avoid if possible: Continuous pour is always better

The Bottom Line

A cold joint is a weak seam formed when pouring new concrete against concrete that has already started to set. It creates a weak point and potential failure area. Avoid cold joints by pouring continuously—plan ahead, have enough concrete and workers, and complete the pour without stopping. Continuous pouring ensures strong, monolithic concrete without weak seams.

Need help planning your concrete pour? Contact Local Concrete Contractor. We plan pours carefully to ensure continuous placement and avoid cold joints.