We had a concrete driveway poured on Nov. 13, 2010. In March 2011, it became clear that the job was botched. We met with the contractor in late March and he agreed that the concrete was defective for whatever reason. The contractor and concrete company have been dragging their feet and ignoring us ever since. I mailed a registered letter to the contractor in August, 2011 demanding some action. We also registered a formal complaint with the Better Business Bureau last week. We think that the contractor is dragging this out to get past the statute of limitations for small claims court. Through research, we've learned that the concrete mixture was way too wet, it was poured too late in the season, it wasn't a winter mix and they didn't cover it with thermal blankets.
What is the statute of limitations for poor contractor's work around my house?

Ontario's Limitations Act limits claims to a two year limitation period beginning on the date the claim (an act OR act of omission) would have/did become known/obvious to a reasonable person. That date, obviously, can the subject of a great deal of argument. When should you have known?

I think you are right on the edge and I personally would file as quickly as possible.