Unusual stains on staggered gable ends

[Tim Fuller]

Good day all,
Can anyone help me to identify what is causing this discoloration of the wood in this attic space? This is a mid 1970's house that just recently (2 years ago) had the roof covering replaced and ridge vents installed. Prior to this new roof covering there was a lack of venting. The only vents were the gable end vents on a house that is 70 plus feet long. The moisture readings were low and the white stains around the edges of the dark stains does not easily wipe off.

[chris mcintyre]

OK, here is my WAG:

This has nothing to do with ventilation.

The house originally had (cedar?) siding, the carpenters chose not to put the black board in the small parallel gable space, leaving the siding exposed in the attic, the siding was stained and sealed on the exterior.

When it rained the cut edges against the roof wicked moisture into the siding, since the outside was sealed the moisture evaporated into the attic leaving behind mineral deposits (efflorescence) and faded the siding over the years.

WAG 2:

Vinyl siding has been installed over the original siding.

[Tim Fuller]

Thanks Chris,
WAG 2 is spot on. A couple of years ahead of the roof was vinyl siding. They covered over the western cedar that was the trim and siding at the back of the house. If you take into account the condition of the rest of the house the homeowner probably sealed that siding rather frequently.