In most cases your existing framing is sufficient, but you will need to make sure that it can support 11 lbs. per sq. ft dead load. Most lumber companies are usually able to help you with this calculation. You will need to give them the size of the deck joists 2x10, 2x12, 2x8 etc. and the length of joist from the house to the support beam. They should be able to let you know if it can support 11 lbs. dead load. If it can support the tile, then you will just need to add one 2x4 sister joist per main joist. If your existing joists do not have enough weight capacity, then you might have to add a sister joist that is larger than 2x4.
