Mitigation Principle: Fulfilling Duty and Creating Opportunity

1. Introduction

In construction projects, adverse events—delays, defects, market changes—are inevitable. How a party responds to such events can determine the size of financial loss, the likelihood of dispute, and the strength of ongoing relationships. The principle of mitigation is central to this response: it governs what steps an injured party must take to minimize the impact of another’s breach.

Drawing on both construction industry practice and contract theory (Goetz & Scott, 1983), this article explains: How contractors can prove they have mitigated, whether mitigation is a legal duty, a contractual obligation, or merely a commercially sensible choice, how the costs of mitigation are treated, and how mitigation operates under law and contract.

2. Defining Mitigation in the Construction Context

In simple terms, mitigation refers to the steps taken to reduce the impact of damage once an event has materialized.
Examples in construction include:

• Resequencing helps maintain progress despite delays in materials.
• Deploying temporary works to allow partial operation of a facility.
• Resequence procurement to avoid further disruption after a variation.

3. Duty vs. Obligation in Mitigation

Term	Meaning in Law/Contracts	Example in Construction
Duty	A responsibility imposed by law (common law, statute). Applies even if the contract is silent.	Under common law, an injured party must take reasonable steps to reduce loss after breach.
Obligation	A responsibility expressly stated in the contract.	Under common law, an injured party must take reasonable steps to reduce loss after a breach.

4. The Doctrine of Avoidable Consequences and the reasonableness of measures

The doctrine of avoidable consequences prevents an injured party from recovering damages for losses they could have reasonably avoided. It has two aspects:

• Negative – You cannot passively incur avoidable loss.
• Positive – You can recover reasonable costs of actively mitigating loss.

This is not about helping the breacher; it’s about avoiding waste. Courts measure reasonableness from the perspective at the time of decision, not with hindsight.

However, the mitigation measures must be commercially reasonable and Plaintiff can afford them. In other words, mitigations become a duty when the plaintiff is financially capable of mitigating.

4. When Does the Duty Arise?

Under common law, the duty to mitigate typically matures after breach or after a clear and unequivocal repudiation. Economic theory supports this—requiring mitigation too early could trigger unnecessary costs and invite opportunism.

In a construction context:

• A mere risk of delay does not yet trigger the duty.
• A formal notice of default or explicit refusal to perform will

4. How Mitigation is Treated Under Law and Contract

4.1. Common Law Principles

• Duty on the injured party: If a contractor suffers a delay due to the employer’s breach (e.g., late site access), they must take reasonable steps to minimize the delay and cost.
• Reasonableness Test: Steps must be reasonable—not heroic or commercially ruinous.
• Burden of proof: The burden is on the claiming party to show they acted reasonably; the burden is on the defending party to prove a failure to mitigate.

4.2. Under Construction Contracts

• FIDIC (e.g., Red Book, Sub-Clause 8.4 & 8.5): The contractor must use “reasonable endeavors” to prevent delay and mitigate its effects.
• NEC3/4 (Clause 61.3 & 63.7): Early warning and risk reduction meetings form part of the mitigation framework.
• CCDC2 (Canada, GC 6.5.3): Contractor to take reasonable steps to minimize the effect of delays.
• JCT: Contractor must proceed “regularly and diligently,” which implies a duty to mitigate.

5. Cost of Mitigation

Scenario	Recoveranble or not	Notes
Mitigation due to the other party’s breach	It may be partially recoverable if the event is a “compensable delay.”	Must be demonstrably reasonable and linked to the breach.
Mitigation due to neutral events (e.g., weather)	The party suffering the loss, unless the contract provides relief	The party suffering the loss, unless the contract provides relief
The party suffering the loss, unless contract provides relief	The party taking the action	Costs beyond “reasonable” may not be recoverable.

The duty to mitigate—or the “doctrine of avoidable consequences”—requires that a harmed party take reasonable steps to minimize their losses. Costs reasonably incurred to reduce damages are typically recoverable as part of the main claim. Conversely, a plaintiff must not exploit the situation to inflate losses or damages through unreasonable or self-serving actions.

6. How Mitigation is Done in Practice

1. Early Detection – Timely identification of the risk (early warning notices, site monitoring, supplier tracking).
2. Impact Assessment – Notify the employer with the potential delay/cost impact and potential recovery measures, and provide recommendations.
3. Considering alternatives: resequencing, changing means and methods, changing subcontractors, changing working hours, and reducing manpower.
4. Consultation & Agreement – Notifying and agreeing with the other party before taking costly steps.
5. Execution & Monitoring – Implementing mitigation, tracking its effectiveness and adjusting to provide the least cost impact.
6. Documentation – Keeping contemporaneous records (meeting minutes, correspondence, cost logs) to demonstrate reasonableness.

7. How a Contractor Can Prove Mitigation

Courts and arbitral tribunals require clear, contemporaneous evidence that mitigation steps were actually taken and were reasonable. Key proof elements include:

• Notices and Correspondence
  • Early warning notices, delay notifications, and records of employer responses.
  • Emails and letters proposing and agreeing to mitigation measures.
• Programme Records
  • Updated schedules showing resequencing, acceleration, or resource reallocation.
  • Baseline vs. mitigation programme comparisons.
• Cost Records
  • Timesheets, invoices, equipment hire agreements, and supplier change orders.
  • Clear segregation of mitigation costs from normal costs.
• Meeting Minutes & Instructions
  • Evidence of collaborative discussions on mitigation.
  • Instructions from the employer or engineer confirming scope and cost responsibility.
• Photographic and Video Evidence
  • Before-and-after site condition documentation.
  • Records of temporary works or alternative access solutions.

9. Risks of Failing to Mitigate

• Damages Reduction: Courts/arbitrators may reduce claim value for avoidable losses.
• Breach of Contract: Failure to follow contractual mitigation obligations may be grounds for default notices.
• Relationship Damage: Perception of inaction can harm trust and collaboration.

10. Strategic Considerations for Senior Managers

• Balance Legal Compliance with Commercial Sense: Avoid measures that cost more than the loss avoided.
• Engage Stakeholders Early: Involve the owner, engineer, and subcontractors before committing to expensive steps.
• Ensure Recoverability: Secure written agreement on mitigation scope and cost allocation where possible.
• Embed Mitigation in Risk Registers: Make it part of proactive project controls, not just a reaction to problems.

11. Conclusion

Mitigation in construction is not an optional courtesy—it is an enforceable expectation grounded in both law and contract. The most successful claims arise when a contractor acts promptly, chooses cost-effective measures, and keeps meticulous records.

References:

The Mitigation Principle: Toward a General Theory of Contractual Obligation

Duty to Mitigate

Reasonable Mitigation Obligation