Every reason I have been reluctant to weigh in on this thread , and others like it in the past, has been touched on in the above well said replies.
As strait forward and as common sense driven as such an effort is, when stripped down to what it is you are doing…
Lifting a compromised building, which might well be a deck of cards, can sometimes be, extremely dangerous. The key to understanding the danger and how to deal with it, is understanding how the building works, that, and how it is working in the condition it is currently in.
Common sense is a powerful tool, but might not be enough. Experience not only counts for much, but constantly hones that sense, not always so common.
Pete’s point about shimming off, is right on, more than that, following your jacks with shims is key.
You can’t just bed a jack, put a timber post on it and start jacking…
Hydraulic jacks are subject to catastrophic failure, even top dollar ones, cheap ones are a recipe for disaster, if a jack fails with 8” of ram out, and you are not shimmed off , the building is not likely to stop falling at that eight inches. And where are you, under the building, right next to that jack.
Cribbing, and knowing how to use it is how this works, you follow the frame up with the crib, and you shim off till there’s room for another pair of crib block…
There are ways to grab a post low and minimize the cribbing, but that’s another whole discussion.
Often as not, the frame wants to fall together, listening is a huge part of it, it’ll tell you what it wants, withdrawn tenons might well want to go home, a little lateral nudging can be part of it, but unless a building has a serious list, it’s often simpler than first glance might suggest.
Which is not to say, Dan doesn’t have this in a nutshell, do be super careful -
Pete, I don’t know how our paths haven’t crossed before now, I’m working out in your neck at the moment, on the Contoocook RR Bridge, swing by
