Jacking + Supporting a Sagging Beam

[gscallon]

Kevin,
My garage is 20 feet wide and has 2x6s running across on 24" centers. No center beam. Just 20' 2x6's running across. Even though the shallow roof pitch meant that there wasn't much attic space up there, I wanted to strengthen everything and put a plywood floor in to store stuff. I knew that the span tables would suggest that 2x6's are way too light for going 20" across, especially with stuff stored on them, but I wanted to see if I could strengthen things up to make it work.

If you look up to the graphic that ez-duzit posted, I'll explain what I did. I added vertical hangers to every one of my joists, about 4 feet in from the wall ends. I used liquid nails and screws to secure them flat to the joists on the bottom and the rafters on the top. Secondly I added some of what the graphic calls "ridge collars". These held the upper part of the rafters together. These two things strengthened my joists a huge amount. So much so that I now have a 1/2" plywood floor installed and am storing stuff up there. (and it's rock solid, even with me crawling around up there)

Now I'm aware that the span tables frown on this but it worked really well for me and didn't take a ton of work. In your case, since you don't even want to store stuff up there, it seems like a viable option.

Because your main joist is sagging, you may also want to jack it up and sister some parts of it to help with the sag. I can't help you there. I would suggest however that while it's jacked up, you consider doing the strengthening I did and then see how it sits. You may find that you don't need any center posts, i-beams or anything else.

Good luck.
-Greg

 

[DekeT]

After removing all the weight of the OSB, shore each cross tie to level, one at a time. And install a hanger, in the center, tied to a ridge collar, before removing the shoring.

Simply a bad idea to adjust the pieces individually. You will likely subject the members to an overstressed condition if not done as a whole. You should have all the members to undergo uniform stresses and movement while restructuring.

 

[DekeT]

Dimensional lumber, being most affordable, has sufficient thickness to place many extreme fibers where they will carry the loads. A thin sheet of metal does not.

You needn't take my word for it--look it up: an I-beam vs a flitch beam.

Ignoring for the moment that a flitch beam has a continuously supported steel center, you need to locate your strength of materials notes from class.

 

[PugetDude]

Stick to what you know.

I did.

And, so you can broaden the depth and breadth of your engineering expertise, here are a couple of handy flitch beam design links:

http://dcstructural.com/pdfs/technical/1997_design_guides_for_flitch_plate_beams.pdf

https://books.google.com/books?id=_...f07D_k#v=onepage&q=flitch beam design&f=false

Not saying that a flitch beam is better than a W, I or S -beam, just that a properly sized flitch beam may be a viable alternative for the OP, since he can probably handle the fab and install himself.