Help With Adding Floor Joist Support to Cabin

[papakevin]

We have a cabin at our camp which isn’t built on a solid foundation. The front part was constructed on an old concrete pad/driveway. The rear of the cabin has 4x4 posts in concrete for the framing and floor joists are just off the ground (maybe 6-8” of clearance. I have an interior wall with two doors which appears to be sagging because the door frames are no longer square.

Since access is limited underneath, I guess the only option to fix is to remove the finished floor and subfloor to get access to floor joists. Once I get this opened up, what are my options for bracing the joists/wall besides simply putting concrete blocks, bricks, or pressure treated lumber on the ground to build it up and support the wall? Best photos I can get for now are attached.

 

[Snoonyb]

Is the sagging wall, perpendicular or parallel with the floor joists?

 

[papakevin]

Is the sagging wall, perpendicular or parallel with the floor joists?

From what I can tell, the wall in question runs along the beam highlighted in red. I’ve attached a photo without the markup as well. Later this week I’m going to remove the black drain pipe in the photos and clear out some of other junk underneath so I can get a better view of what is going on.

 

[papakevin]

Got to the cabin yesterday and made progress. Found the main support beam is attached to a 4x6” post in the ground. A 2x8 is the attached on both sides of the post to provide a point to attach the additional floor joists.
Since access was limited, I pulled back the bedroom carpet and cut myself a 4x5’ access point along the beam. I used a farm jack to slowly and barely raise up the floor so I could add temp support. I ordered a small specialty screw jack from Ellis, so will be fixing it right later.