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.
How to pin up saggy roof.
Next place your piece of plywood and styrofoam foam side up against the damaged roof decking.
This is the most inexpensive way to stop a sagging headliner.
Remove the jack quickly and set the iron onto the entire beam.
Drive the remaining carriage bolts into the two by six rafter and tighten them all up.
These pins have a pointy end that twists into the head.
That s how to fix a sagging roof.
Now add collar ties from one side of the rafter to the other.
Place the jack back underneath the beam but this time under the iron piece.
Additionally if your roofer has used material that is much heavier than your previous roof it can sag for the same reason.
Push up on the plywood until the foam is touching the underside of the roof decking.
Non foundational reasons for a sagging roof.
Two or more roofs on one structure spell trouble.
Depending on the degree of sagging your contractor might need to use jack posts to raise the roof before installing any reinforcement.
Then lower the jack down a little at a time so that the metal can take the weight of the roof.
The home may not be designed to support the weight of this extra roofing material and it will sag.
First perform step 2 except keep the string under your beam and off to the side a bit to make room for some framing.
When you push it against the backboard you need to twist it and the headliner will stick in place.