Can I sue a property manager for negligent management of my building in Ontario?

Yes. A property manager engaged to look after maintenance, tenant relations, insurance, or building finances owes a duty to perform those services to the standard of a reasonably competent property manager, and a clear failure - ignoring a known maintenance issue that leads to damage, letting required insurance lapse, or mishandling building funds - can support a professional negligence or breach of contract claim, or both.

As with other professional negligence cases, an unfortunate outcome alone isn't enough; you need to show the manager's conduct fell below what a reasonably careful manager would have done given what they knew or should have known. The management agreement itself matters a great deal here, since it typically defines exactly what the manager was responsible for, what discretion they had, and often includes limitation-of-liability language capping recoverable damages. For a condominium corporation, the board's own obligations under condominium law can also come into play, since the board remains responsible for the building even while a manager is delegated day-to-day tasks. Damages are generally the cost to remedy the harm the negligence caused, supported by repair estimates or financial records.