Hi DIYer's!I've got a 2 story brick house from 1915 with a noticeable sag in the kitchen beside the basement door. The problem is pretty clearly centered on the post directly under it. I can take pictures wherever needed to get a good idea of what's going on.The post that's settling and causing the sag is situated at the center of the T between the joist running from my main support beam to the concrete foundation at the basement door, and a 4x4 put in to run under the joists (the sagging one included) along the length of the basement stairs where they were cut off.The post itself is a 4x4, set on a beveled wooden post cap to act as a footing. This footing is rotting into a greasy lump on the floor due to occasional water in the basement. It's allowed the joist to settle about an inch, inch and a half at the worst point; the footing is still there, it's just dying. The sag is gone after about 3 feet, so it only appears to have affected this joist.I've had a structural engineer in; they see no sinking of the concrete footing below the post (if there even is one), so to them it's a 'simple' job that doesn't require the $1700 it would cost me to get a plan from them.The basic plan they gave me; jack up the 4x4 beam directly attached to the post (slowly) to level the floor, shoring on either side of the post along the joist until the sag is unnoticeable, and the rotting post comes free of the floor. I can then remove the post and rotting 'footing'.Then, the plan is to clean the concrete underneath and build a concrete plinth block in to keep the new post out of the water. They said I could either cut down the existing 4x4 to remove the rot, or install a whole new post altogether, but they think a 4x4 is fine due to how little real weight it's supporting.Then, once everything's attached and braced properly, we would slowly back off the shoring posts and let the new post take the weight.My main question (and what brings me to Reddit), is what's the safest DIY method of actually jacking and supporting the job while I remove the post to do the rework?I see a lot of online topics talking about using hydraulic bottle jacks for the actual lift, and shoring with adjustable lally columns/screw jacks. The structural engineers said a 20 ton bottle jack would be overkill for this job, and that I could probably just use a 12.I'm not 100% sure I trust the bottle jack. I've heard a lot of horror stories about them kicking out, and I've seen a lot of comments about how they're not suitable for this kind of work because they could burst. I'm expecting the lift to take a few weeks, and I've read that it's not a good idea to leave these set up, even with additional shoring posts.A lot of people (with varying levels of DIY experience) have suggested getting three screw jackposts rated about 12000 lbs, and setting them up on the 3 supported sides of the post (with spreader boards, steel plates, or patio stones underneath, and turning 1/8th turn per day until the floor above is level, and slip a shim under the rotting post each time to keep things steady. When level, I'd then remove the shims, then do the fix, and then screw down the jack posts a bit at a time.Of course, that brings in the people who then disagree, because screw jack posts are supposed to be for secondary support, and not actually lifting.Fellow DIYer's who've done localized lifts like this before, what did you do? via /r/DIY http://bit.ly/2Gav2S2
