You would not really have a service disconnect to an outbuilding,since what you are describing is a branch circuit off your main panel. What you may require, depending on how much power you are bringing to the outbuilding, could be some kind of sub-panel. Be sure to read CEC 10-208. You are allowed two 15 amp circuits to the outbuilding without a subpanel-but I cant find that rule, be sure to talk to your local AHJ to check local rules also.
