jacking up joist FAQ

Get rid of the antiquated trap and lead bends, install a proper tub trap, and sister on a full depth joist that's glued and screwed to the existing compromised joist, that sits on the wall plate and extends ~2' minimum past the notched area. Drill holes or notch as per code as necessary.

A 2x4 might work. You could also try using a 2x6, 2x8, 4x4 or 6X6. If hammering doesn't work out well you could try putting a jack under it. Perhaps a bumper jack would allow you to stabilize the assembly by wrapping some rope around the board and the top of the jack. The best technique would to place cribbing on the floor until you are high enough to put a jack under the joist. You can look here for pictures and methods.

I understand that jacking up a joist has to be done over time (weeks) to allow everything to equilibrate. 1/4" doesn't seem like a lot, so you'll probably be okay.

That might work. 2x4's will bend though. I have a small bottle jack as well as a floor jack. You can get a bottle jack pretty cheap. If you use a 4x4 it won't bend.

RicodJour wrote the following:

And change those copper pipes using proper pipe fittings. The one on the left looks almost flat

only

Just because the plumbing is old school doesn't mean it all needs to be replaced. That's soft copper pipe, not rigid. Bending it is ok.

Make sure you bolt the angle iron on at multiple locations. And run it several feet out from the cut in the joist. You can't transfer a lot of load to it and then expect one bolt hole near the edge of the joist to carry it without splitting the joist where you attach the angle iron.

s only

might be better off sistyering a couple 1/2 steel plates on either side of the sagging joist, clamp both steel plates together drill holes thru both so they match, then put in place and bolt together

Attaching the steel angle, if it would give enough support, would be the least complicated way. 2"x2"x 1/8" L beams on each side of the joist.

I'm a little worried that if I put too many bolt holes in that thin 2" x

I have looked into the other methods and they have problems. If the joist were headered off, the header would have to have like 4 holes drilled through it for the copper water supply pipes. I can't sister it, I talked to the plumber this morning and he said he can't find bathtub drain plumbing that would leave the hole in that joist clear. Apparently they used to make plumbing that would put the drum trap in the space between joists, but he said he can't find it. If anyone knows otherwise, please tell me of it. That was my first thought of course - sister the joist and use drain plumbing that would involve only a small cut in the sister.

Laura

I get the impression that the leg of the angle adds strength. The joist is both bending where it was cut, and shearing a bit at the edge of the sill plate. I'm not sure whether the leg of the angle adds shear strength or bending strength, but both seem to be needed.

I would have to clamp the steel angles on. Drilling one hole through both angles seems like a good idea. Since the joist is 2" wide, I would need clamps with at least 6" gap.

Could it be straightened out with a jack, though? Or since it's a small area that's bent a lot, is it permanently like that now? I guess I could try jacking it up a bit and see what happens.

Laura

Oh, you mean 1/2" steel plates - say, 2" wide? That would also be strong enough? That seems reasonable.

Laura

You don't need to bolt the iron to the joist where the joist has been cut. And if you use angle iron you don't need to bolt it to the joist where the joist sits on top of the sill plate either. The horizontal side of the angle iron will sit on top of the sill plate. Carry the angle iron a good several feet past the cut and use 3 or 4 bolts along that part. As another poster suggested angle iron on both sides bolted so it clamps the joist would be good. If you can't do that use good sized washers.

the vertical bit of the steel provides the most strength in the sense of keeping the joist from bending and the floor from sagging. So if you can get an asymmetrical L-channel it should be installed with the long leg lagged to the joist. C-channel would be another option. But Bob is right in that for strengthening an existing joist, a plate is almost as good...

nate

Again - *can the sag be taken out of the joist by jacking it up* ? It's bent over such a short length, it's likely permanent deformation rather than elastic bending. I know people take sag out of joists by jacking them up. But maybe that works when the sag is over a greater length and it's elastic bending. Maybe jacking up my joist at the bend - the cut place - would just make it crack. Laura

Here's how I would proceed. Jack it up so that the top of the joist is just a little higher than level. Then attach angle iron to both sides of the joist with the angle iron firmly against the sill plate. Sandwich the joist tightly. Let the jack down. Basically transfer the floor load from the good section of the floor joist to the angle iron then to the sill.

Borrow or rent a jack-post.

DO NOT use a bumper jack or Jack-all on a 2X4 for this job. There is a tool made for the job, called a jack-post. It has a screw-jack built into the one end, and is (generally) adjustable for rough height bu telescoping and installing a big pin. Any contractors equipment rental place should have them available - or worst case you buy one from home despot, lowes, or who-ever.

Probably doesn't matter if the joist cracks since you plan on adding steel to it. 1/4" is not much in houses.

That's what I was going to say. Knocking a 2x4 into place is okay for something that won't crack if you push it too far, or something that can crack and it's okay, but Laura needs a lot more control about how high she lifts it. None of those jacks give enough control either. With a jack-post she'll be able to lift a millimeter at a time when it's getting near the right spot.

I don't think it's okay if the joist cracks, plust there is other stuff around it which has never flexed in the opposite direction.

By 2" wide, you mean 2" vertical? Why limit it to 2" and not 4 or 6? Because the pipes are in the way?

I don't know if a full 1/2" is necesary, but ther's an awful lot I don't know.