1 2 inch thick angle iron.
Fixing sagging roof over garage.
Sagging rafters can lead to serious problems with the entire roofing system.
If you notice that there is a visible dip in your roof chances are you have a problem with one or several rafters and you may soon be facing more issues like water leaks bowed out walls or your roof caving in on you.
Use instructions from my page how to fix a sagging floor before you continue trying to fix the roof sagging issue.
The first step is to the basement first.
Any sagging will gradually be lifted and by the time you have finished the garage roof repair your roof should but upright again.
Check the ceiling for sagging by attaching a string on one end of the beam and run it along the bottom edge of the beam.
Step 4 strengthen the beams.
If necessary use something to force the roof up while you work the beams into place and fasten them.
I prefer the term mid span cross tie to collar tie because i associate collar ties with placement high closer to the ridge.