A sagging roof line may original from the ceiling s horizontal rafters.
Garage roof trusses sagging.
Finally make sure stored items are securely locked in place.
Even ceiling cracks can be caused by damaged trusses or downward pressures.
To hold them up until the decking of the roof is placed on top a 12 foot 1 inch by 4 inch piece of lumber is used.
This repair will keep the trusses from sagging.
Then slowly allow the trusses down.
If your ceiling drywall is sagging between joists sometimes called pillowing it s probably on the top floor and attached to the roof trusses.
If you have traditional site built roof framing your storage capacity depends on the design of the framing.
Typically they are lapped and then toe nailed together in its center so that the correct length can be achieved.
You may find that several are in need of straightening and that some of the sheathing must be replaced.
One good thing about wood construction is that failures occur slowly and with a crack or split in the wood.
When the framing of the roof is put together quite frequently two of the ceiling rafters will be fixed together as this will create a much longer span.
Sagging rafters may be the result of having framed the roof with lumber of dimensions smaller than current building standards such as using 2x4s or 2x6 s or there may be damage to the framing from insects or rot.
If so i bet the installers used 1 2 in.
If the framing is sound and problems are not found elsewhere but the roof still sags the problem might have originated because of poor installation of the plywood sheathing or shingles.
Are doors sticking or jambs out of square.
When all the trusses are installed and the first row of decking is on this brace is removed.
However a bigger problem is nailing the new web member to the ridge peak of the truss and there will be 2 members nailed in this location.
So you should start by inspecting the roof from the under side or attic.
However it is important to fix the rafters before doing any other work to the roof.
The first step is to find out how many rafters are sagging and if anything else is damaged.
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.
It can be nailed temporarily to each truss as the next truss is put in place.
Usually trusses are put 24 inches apart.