I need to sister some joists in the basement. I have a 20-ton Husky bottle jack that can do the job. Most people say to only raise the joist 1/4 inch and leave it that way for a day before raising it again. Will the bottle jack be able to maintain that for the day or do I need to get another post to hold it in place?
If the jack doesn't creep (has good seals) it will stay where you put it. But no harm in putting a post under it too. Are you just jacking the centre of the joists trying to take some sag out? Or are you lifting things up above as well?