Executive Summary: Key Legal and Evidentiary Issues

• The court considered whether to authorize the late filing of a supplementary expert report in a construction defect case.

• Pro-Tec sought to file an updated engineering report after deadlines had passed and without prior notice to the opposing party.

• The Tribunal applied the discretionary criteria established in Quebec case law to assess the fairness and necessity of allowing the evidence.

• Despite procedural lapses by Pro-Tec’s legal team, the court emphasized the importance of complete expert testimony in a technically complex dispute.

• The risk of prejudice to the defendant was mitigated by procedural safeguards, including the right to file a responsive report.

• The court allowed both the late expert report and a responsive modelling calculation, prioritizing the integrity of the trial process.

Facts and procedural background

In Constructions Pro-Tec-Toit inc. v. Rénovation 418 inc. (Garage Expert), the plaintiff, Pro-Tec, sued its subcontractor, Garage Expert, for construction defects related to roof trusses installed as part of a building renovation project. The dispute centered on alleged structural malfunctions and the quality of work delivered by Garage Expert. Prior to filing its claim, Pro-Tec retained an engineer who issued an initial expert report in November 2023.

The case was set for trial, and procedural timelines were established during a case management conference in October 2024. Garage Expert submitted its expert reports in February 2025. Despite this, Pro-Tec filed a twelve-page supplementary expert report in April 2025—well after the prescribed deadline—without having informed the court or opposing counsel in advance of its intention to do so.

Garage Expert opposed the filing, citing surprise and procedural unfairness. Pro-Tec filed a motion requesting permission to include the new report, relying on article 248 of the Code of Civil Procedure.

Judicial analysis and findings

The court, presided over by Justice Dominic Roux, reviewed the request under well-established discretionary criteria for late filings. These include the reason for the delay, potential prejudice to either party, the responsibility of counsel, and whether the evidence is essential for justice to be served.

The court found that although Pro-Tec’s counsel failed to mention the possibility of filing an updated expert report during prior conferences, and although no record supported their claim of prior notice, the delay was not attributed to bad faith by the party itself. Miscommunications and changes in legal representation contributed to the delay.

Importantly, the court noted that the supplementary expert report was necessary for Pro-Tec to present a complete technical argument at trial. Its exclusion would seriously prejudice Pro-Tec, while the prejudice to Garage Expert—though real—could be mitigated by allowing it to file a responsive engineering model. Both parties’ experts were already scheduled to testify, and the additional evidence would not delay trial or disrupt the proceedings.

The court emphasized that expert reports serve the function of helping judges understand complex technical issues and that the integrity of this process outweighs the procedural missteps. Allowing the supplemental evidence aligned with the principles of proportionality, fairness, and the pursuit of truth.

Conclusion and outcome

The court authorized Pro-Tec to file the supplementary expert report within ten days and permitted Garage Expert to respond with its own engineering model within thirty days. No costs were awarded. The ruling highlights the flexible and discretionary nature of procedural management in civil litigation, especially when expert technical evidence is critical to resolving the dispute. The court balanced procedural discipline with the broader imperative to render an informed and fair decision based on a complete evidentiary record.