Although most cracks are usual harmless, it’s important to make sure to let an expert analyze it.  Toronto has some of the most diverse climate, so it is not uncommon for cracks to arise in concrete.  When temperature changes occur, concrete will either expand or shrink.  The hotter the temperature, the more concrete will expand and put pressure on things in its way, while the colder the temperature, concrete will shrink and press on itself.  These change in temperature put pressure on the concrete which is why we see so many cracks occur on concrete in Canada.  When these cracks get within the concrete, it can severely damage the structural integrity of the concrete leading to very expensive repairs.