This young couple recently bought a home, and wanted to stabilize an upper floor deck, which was sloping due to settlement of the supporting footings. The house is located adjacent to a fairly steep slope, and each time heavy rains occurred, the hillside supporting the footings shifted very slightly, so that the settlement was gradual but continuous. The footings were located too close to the top of the slope. Just looking at the hillside, it was obvious to me that eventually the footings will slip too far and the deck will fall. It might take years, but in the end that is inevitable.
The previous owners had, over the years, tried many sorts of fixes, some of which were not exactly sensible. In any event, we provided recommendations on how to fix the problem permanently. Two options included using diagonal braces back to the homes foundation, and using driven pipe pile foundations. Both of those will let the hillside do what it will, without affecting the deck.