rusty nails/water stains

[Greg Jenkins]

What is up with this? During the attic inspection, I noted water stains around the roofing nails. Some of the nails appear rusty. The roof covering is an asphalt shingle and it appeared in good condition with no visible defects. I have seen this condition on roof coverings that were failing but not on shingles that are in good condition. There was only one layer of shingles present. What am I missing?

[John Arnold]

Poor ventilation / condensation on nails?

[Greg Jenkins]

Yes - good call. The soffit vents were partially obstructed by insulation. Still seems like a lot of staining but I guess it doesn't take much.
Thanks

[Jim Robinson]

Sometimes you will also see little rust spots on the top of the insulation, where the water has dripped off the nails. That's a good sign of condensation in the attic.

[Eric Barker]

Greg,

I have such stains in my attic. In the real world I think these can be expected after a period of time and I ignore them when the home has some mileage on it.
This is especially true when all else looks good in the attic. I have a typical 1979 colonial home with 16 soffit vents, 2 gable end vents and 5 roof vents on the main roof and occasionally the plywood decking still can get damp.

As with many things we look at, taking into consideration the age of the house is important when considering the significance of a condition.