Rafter ties another cause.
Sagging roof ridge beam.
This may have been caused by any number of factors.
The beam is attached to both exterior walls and to the bottom of each sloping rafter to give the roof strength.
Straighten out your old house s sagging roof and get rid of those cracks in the wall with these easy to follow steps.
Ridge beam or ridge board sagging or damaged roofs may sag because a ridge beam or ridge board is cracked or damaged.
The most common cause of sag at the roof ridge is loss of triangulation due to failure of the bottom leg of the triangle which makes the peak of the roof sag and top of the walls spread outward in the area of failure.
If the beam is not properly nailed it can also pull loose and this contributes to.