Sagging Rafters

[Andy More]

I looked at a duplex yesterday that I'm scheduled to buy next week. I mentioned this in another post. I did an inspection of the property on Friday.

There is a section of roof where the rafters appear to be sagging. Its not just sagging between rafters. I took a pic but the sagging it not as noticeable in the pic as it is in person.

flickr.com/photos/9192910@N05/5065380783/

The overhang portion of the roof on the gable end(right side of pic) is not sagging at all. I'm assuming that exterior wall on the right side is keeping the roof from sagging. But, just inside gable overhang is where the rafters are sagging. Sepecifically its sagging towards the lower 1/3 of the roof.

The ceiling below the sagging portion is a vaulted ceiling. There are no cracks or anything in the ceiling or the wall that the rafters rest on. The exterior wall(brick portion in pic) does not seem like there has be any movement.

How common is a section of sagging rafters and is it something I should be conerned about? The property is about 15 years old. I believe the rafters are 2x6 and 24 inches on center. Not sure of the thickness of the roof sheathing