We had our roof and sheathing replaced on our townhouse last winter because a roofer believed that condensation had damaged the sheathing and rafters. Melted ice was dripping from the nails and frost covered the sheathing, rafters, and nails. The roofer sistered the water damaged rafters and replaced sheathing before shingling.
This year, before the first snow, I noticed darkening on the top side of several rows of rafters. The board running along the base of the roof behind the gutters is also wet inside the attic on the back side of the house. The roofer is baffled. The new rafter boards sistered with the old wet ones are not wet. Only the previously damaged pieces are wet. The decking is dry. The roofer believes this is due to condensation, but in 30 has never seen this happen before.
I did notice that the roofers did not spread the insulation evenly after replacing the roof. Could this cause only the rafters at each end of the roof to become wet? It is only on the four rows in from each side where our house is attached to another. The center rafters are dry except for the ends at the bottom end of the roof.
Any suggestions as to what it might be or who I need to contact would be most appreciated.