A practitioner can be sued in contract, in tort, or both. Central Trust Co. v. Rafuse (1986 SCC) confirmed concurrent liability: where a duty in tort arises independently of the contract, a plaintiff may sue in either contract or tort (subject to any contractual limitation of the duty) and choose whichever is more advantageous. Often the limitation period or scope of recoverable loss differs.
Central Trust call-out: A professional owes duties both under the retainer (contract) and in tort. The client can frame the claim either way unless the contract validly limits the tort duty.
Other liability-spreading doctrines:
- Vicarious liability: an employer is liable for the negligent acts of employees committed in the course of employment. This is why firms, not just individuals, are sued, and why employers carry insurance.
- Joint and several liability: where two or more defendants cause a single indivisible loss, the plaintiff may recover the full amount from any one of them; that defendant then seeks contribution from the others. A "deep-pocket" engineer can thus pay more than its share and chase reimbursement.
Note that being incorporated or employed does not shield an engineer from personal liability in negligence for their own professional work. Professional duty attaches to the individual practitioner who does or seals the work.