Fixing a sagging roof by bolstering the beams bolstering the beams of your roof is another solution to repairing a sagging roof however it is often something that requires assistance from another able bodied person since beams can be extremely heavy.
Fixing saging roof obver garage.
Should the bottom cord of one or more trusses be sagging or damaged it may be reflected in a sagging ceiling or if the roof is over loaded to heavy then the downward pressure may cause the sagging.
Now add collar ties from one side of the rafter to the other.
First perform step 2 except keep the string under your beam and off to the side a bit to make room for some framing.
Gradually work along all the beams pushing the roof up as you go.
Once you have established how much the roof sag needs to be jacked up lay a 2x4 plate across the ceiling joists and nail directly under the ridge of the roof.
Sagging ceiling could be an indication of framing issues some of which could be related to the roof.
Step 4 strengthen the beams.
If necessary use something to force the roof up while you work the beams into place and fasten them.
Any sagging will gradually be lifted and by the time you have finished the garage roof repair your roof should but upright again.
With the joist back in its original position place one section of the angle iron on the uppermost section of the rafter just before the area where it is sagging or broken.
With a pair of rafters pushed apart to straighten the sagged roof a new mid span cross tie will be nailed in place.
You will need to remove the shingles and the old decking however which means there will be an exposed hole in the roof.
If the sagging roof is due to rotting or warping roof decking the repair will be much easier.