The cantilever design of a deck building is one that many people are not well versed in. The traditional deck is one where the beams and joists are supported fully by the concrete footings on each corner. With the cantilever design of deck building, the beams can run past the piers. While this is great in some respects, there are also a few drawbacks.
The biggest advantage to the cantilever design is that the beams and joists can run past the concrete piers. Because of this the decks can be up to 4 feet wider without having to change the span ratio or adding more support. When building the deck it is important to remember that the joists should only run past the footings a certain distance according to the width of the joist itself. A general rule of thumb is 4%.
The normal decking configuration is a vertical placement that runs perpendicular to the joists. With the cantilever design you can lay the decking material with an angle that runs across the joists.
A disadvantage to the cantilever design is that since there is no support under certain areas, there is a spring to the floor. This can cause bouncing, and some bending when under a lot of stress. Over time, this stress can cause fractures in the wood leading to structural failure.