Look for any kind of damage including rot cracks breaks and more.
Home roof sag.
Also inspect the metal or plywood gusset plates used where your wood meets on a truss.
Grab a flashlight and head up to your attic to inspect your roof rafters and decking specifically those where your roof is sagging.
Installing new rafters directly alongside the weak or damaged ones is often enough to correct this problem.
Some roofs sag because of decay to the inside beams and sheathing.
Then inspect the metal or plywood gusset plates.
Using a flashlight inspect the rafters and decking in your attic especially in the areas where your roof is sagging.
Two or more roofs on one structure spell trouble.
This is the easiest problem to repair.
Cracked rafters and trusses can cause sagging.
In a stick frame non truss sloped roof these issues usually cause the roof ridge to sag in the middle giving it a swayback look but can also cause one side of the roof to sag.
The home may not be designed to support the weight of this extra roofing material and it will sag.
If the framing is sound and problems are not found elsewhere but the roof still sags the.
Decay can occur over time due to a number of reasons including leaks in the roof or leaks from guttering or downpipes wet rot or even insect attacks such as termites damaging the ends of the bearings.
Go outside of the house and determine where the sag on the roof would be in your attic.