Using a jack to raise joists

drhowarddrfine

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?

Bonus

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?

drhowarddrfine

That's what I thought but I read an article that gave the impression the bottle jack was good enough. Thanks.

The stupid builders cut about 1/3 of the joist out for a vent. The joist now has a bow in it about 1/3 in from the plate on the foundation. So I guess I have to lift up around the middle.