garage ridge beam repair

I'm a homeowner, not in the trades, so please bear with me.

The center ridge beam of my two car garage has a noticeable sag of 2-3 inches due to a split near the middle of the 2x8 (it could be a 2x10). The beam goes the width of the garage, about 20 feet. This defect seems common in our neighborhood, a bad design. My roof covering is standard fiberglass shingles although originally it had a (much heavier) rock roof. Roof pitch is low, maybe 1 in 4.5. One neighbor fixed his sag by installing a 2x10 or 2x12 beam about two feet below the original and adding triangular bracing to form a truss. This seems like an excellent fix, and would not be too difficult, so I would like to do it too.

My plan is to place the second beam (making sure its well supported all the way down to the sill) and jack up the center of the ridge beam slowly over several days, then nail in 2x6 diagonal bracing. The supporting beam may have to be spliced with about 4 feet of overlap unless I can get one very long beam.

I have a lot of questions:

Should I jack up the center of the ridge beam higher than its level position before adding the diagonals in order to have it closer to level when the supporting jack is removed? and if so by about how much?

Should I also jack up the center of the reinforcement beam (bottom of the new truss) so it bends upwards the same amount? Is a 2x10 adequate?

Should I try to put epoxy into the crack before I jack up the split beam
or don't bother?

Should I try to attach a reinforcing plywood plate or other repair to the break?

I plan to have four sections of triangles, I think they should form a letter "W" like this:

========= 2x8
\ / \ / 2x6
========= 2x12 (probably with a splice for required length)

rather than the opposite like the letter "M", is this correct?
=========
/ \ / \
=========

Any special nailing tricks to pass on such as what type of nails (or screws) to use?

Thanks for any other advice or suggestions.
Robert

 

Before I went to all that trouble, not knowing FOR SURE if the fix will work or not, I would consider stripping the garage off to the top plates of the walls an installing engineered trusses. They WILL work, and it will be easier, stronger, and probably less expensive than what you are thinking about doing. Go to a local lumberyard or truss mfgr.