Jack up that portion of the house and place new footers.
How to lift or jack up sunken floor joists.
Get the jacks under the floor.
After they were in place we hoisted up the 4 x6 x8 beam so that it crossed all four of the new joists sliding the screw jacks underneath.
You cannot jack up a house in one day.
It has to be jacked up slowly over days or even weeks to avoid cracking drywall plaster windows and even structural elements.
Identify the area of the deck that is sagging and locate the support post that needs to be shimmed.
Generally there are posts and beams under the floor joists.
Once the new joists were up we found locations where the concrete blocks could sit flat on the ground so the pressure wouldn t cause them to crack.
Jacking up the deck and shimming the post can resolve deck sag problems.
Step 1 access the area under the deck.
Anything involving 20 ton house jacks will take time.