When is an amendment to a claim a new cause of action?

Dee Ferraro Limited v. Pellizzari, 2012 ONCA 55 deals with when an amendment to a claim pleads a new cause of action.  Basically if the necessary facts are already before the court a claim based on those facts is not a new cause of action.  The Court writes:

 

[5]          The distinction between pleading a new cause of action and pleading new or alternative remedies based on the same facts is set out in one of the seminal cases, Canadian Industries Ltd. v. Canadian National Railway Co., [1940] O.J. No. 266 (C.A.), affd. [1941] S.C.R. 591. The plaintiff sued for damages following the destruction of a cargo of sodium cyanide due to a derailment on the defendant’s railway line. He pleaded that the defendant was a common carrier and that the goods had been damaged. The trial judge allowed an amendment, at trial, to plead negligence. Middleton J.A., writing for the court, held at para. 18 that the amendment was properly allowed – it was not the institution of a new cause of action, but simply an alternative claim with respect to the same cause of action: “The amendment relates to the remedy sought upon facts already pleaded.”