We have a sagging beam over the middle of the kitchen that is supporting a heavy roof and wall load above (1983 construction).
Opening kitchen ceiling, we found a substandard beam composed of nine 2X4s (arranged three up and three wide) attached to each other vertically by some metal mesh rectangles. This beam spans 19 feet.
One contractor wants to jack the beam up before reinforcing it.
Another contractor wants to reinforce the beam with steel in its present position. He says he never jacks up a beam because the entire wood structure of a house is sagging along with the beam and you can't move one part of it successfully.
Is there a rule of thumb about jacking up sagging beams or joists?
To remove this beam altogether would mean gutting the kitchen ($$$).
Thanks

First of all, WOW about that header. Luckily all it did was sag.

If the first contractor wants to jack up the beam make sure he goes into the basement directly under the jack position and install a temporary post. For one action there's a reaction. You don't want him doing damage to your floor.

As to my knowledge jacking up a sagging beam or joist should be done over time. Usually with bottle jacks where you will make a few turns a day on the jacks until its (beam) to a place where its acceptable.

Your second contractor has a valid point. You may jack the beam up but that's about it. The rest of the floor system may not go up kindly. Over time the floor sagged so everything in the house sagged with it. You jack up the beam forcefully and you may have more problems elsewhere.

My vote would to be try jacking up the beam slowly and sees what the effects are. There should be a lot of creeking and cracking. Depending how bad it sagged you may be able to get a little bit out of it.