Portion of new roof sagging

I recently had a full roof replacement on an approximately 100 year old house. During the job, the contractor indicated that if he removed and replaced the wood decking as per the contract (to replace all wood), there would be a visible gap between the roof and the siding so my only option was to add a new layer of 1/2 plywood over the old wood. A small section of the house, over a back mudroom, had a visibly sagging roof. I expected a “full replacement” would fix this issue. After the replacement, the new roof still sags. I asked the contractor about this and he indicated the roof rafters are misaligned causing the sag but that the problem was aesthetic only and not structural. I am concerned that this section of the roof was not done properly and I will have problems at a later date. I also am unsure how they know that the rafters are misaligned without having removed the wood decking (there is no attic on this part of the house so no interior access to the rafters) and that the rafters could actually be damaged. I don’t know much about roofing (besides some amateur online research before this project) and relied on the contractor to give me accurate information and now I’m afraid I may be being misled. Any advice or information anyone can share would be greatly appreciated! Thanks in advance!

The roofer is correct.
Hes already explained it to you
But i will explain it again.

He did a “full replacement”
He installed all new wood.
Now the decking is a smooth as can possibly be.
Ten times better than before.
He doesnt change out your trusses.
That is there to stay.
Our New wood decking/sheeting can only lay as flat/plain as the trusses on the house.

Any wave that was there is the wave that stays.
A roof job would not change that and make your roof members/trusses all straight again.

You paid him to replace your roof
And all the wood the “roofing” fastens into
Not to tear half your house down to make it perfectly plain from 100 years ago.
You would need a general contractor and Thousands more to do that.

I apologize if i am sounding crass or insensitive.


Agree with roof_lover. Perhaps misaligned wasn’t the right term. I would guess sagging was more accurate but I wasn’t on your roof. If the rafters were as good as new and it was the decking sagging, you’d see a series of valleys and humps, the humps being where the rafters are. Other than that, the new decking is installed on top of the existing rafters and is going to follow how they are.