Reinforcing existing ground level deck moving down slope

by Scott
(California )

I have a deck that's settled and moved about an inch and a half laterally over the past 2 years. It's a ground level deck built on a slope and it's moved down the slope progressively. I'd like to drop some more 4x4 posts in to reinforce it. It's ground level so I cannot access it from the bottom/underside. I'd have to add supports from the top.

I have two ideas to do this. My first idea is to add a post in between existing joists and then another joist in between the existing joists so I can get the joist to rest right over the new post. The downside here is that I'd need to remove every floor board to do so.

My second idea was to put the post right next to the join but since I cannot dig right under the existing join due to it being ground level, I would not be able to get the new post to be right under the existing joist. That means that I'd have to tie the joist to the post on the side of the post which is not as strong and supportive. Does anyone know of a better idea or is adding new joists in between existing joists the best bet?

Editor's Commments

This is a tough call. When a deck start drifting down the slope of a hill it means the entire slope is moving. The slope further away from the house will be moving downwards more than the soil close to the house.

Your description of how you plan to solve it is a bit hard to visualize. But usually when this starts to happen you have to focus on the beam furthest down the slope and it may mean digging quite deep with a very wide footing and building an entire new series of footings and beams that the deck can be rested on. If they are deep enough and large enough in diameter they will be harder to move and more likely to resist the forces.

If anyone else has solved this kind of a problem, please share your thoughts and experience.