Unbalanced Rafter Dead Load

[TOLstryk]

I have been asked to provide an opinion on a residential roof project where the insurance company only wants to replace half the roof singles. The home is a 4:12 gable with 2x8 rafters at 16" O.C right at the current IRC maximum span. There are ceiling joists acting as rafter ties and no upper collar tie. The half reroof will result in a 2 psf increase on the new side.

Besides just generally being a bad idea to do half a roof, I am trying to think of any implications a permanent unbalanced dead load would cause. My concern is the heavier side "pulling" rafter ties towards it from thrust and pulling the upper walls slightly out of plumb.

Is there any code commentary for this in NDS or IRC?

 

[XR250]

I do not share your concern. The tension in the rafter tie (or ceiling joist will increase due to the additional load but the walls will move outwards equally (albeit unlikely to be noticeable). The moment and deflection in the loaded rafter will increase however. A 2 psf unbalanced should not be an issue for most properly constructed roofs.