Estimated cost of replacing rotted joists

[Samantha Klein]

Hey all, I looked at a duplex recently where the floors in back section had sunk approx 4-6" and pulled the wall with it in some spots, looks to be sinking towards the middle of the back section. Some of the joists have rot and are weak, the problem is there is only around 12-14" under the house, no crawlspace, they actually had a hole cut in the floor in a closet for access. How difficult is it and how expensive to replace the joists, I would assume they should probably all be replaced, approx 20 of them, would the whole floor need to be removed to work from on top or do you think 12-14" is enough space for someone to work from the bottom? The duplex currently has tenants.

[Samantha Klein]

@Adam Abdel-Hafez Thanks for the reply. The joists are dry-rotted, could be all of them due to no moisture barrier between the dirt floor and subfloor. These joists are 100+ years old. There is only like I said 8-10" of space between the bottom of the joist and the dirt floor. Is filling the empty space in with something hard so the settling stops a possibility?