Siding Stains

[Greg Jenkins]

The siding on this house has what appeared to be dirt stains (similar to what you might find surrounding a air supply register) where the siding joints overlap.
Any thoughts on what might be causing this would be appreciated. I did not see any interior moisture problems.
I did not get the pics rotated before I uploaded - sorry!

[Jerry Peck]

What type of siding? Vinyl?

What is behind the siding?

[Greg Jenkins]

Sorry I did not provide enough info.
wood frame house built in 2003
vinyl siding
osb sheathing
No house wrap or building paper
drywall interior

[Greg Jenkins]

Had a thought - This house has two powered roof vents. The soffit vents were partially obsructed by insulation. Could the vents be pulling air through the wall cavities and dirt is collecting where the air comes in through the joints in the siding?

[Jerry Peck]

vinyl siding
No house wrap or building paper


Had a thought - This house has two powered roof vents. The soffit vents were partially obsructed by insulation. Could the vents be pulling air through the wall cavities and dirt is collecting where the air comes in through the joints in the siding?

That and/or exhaust fans inside depressurizing the house and doing the same thing.

The no house wrap / no felt paper / no WRB to serve as a retarder to air flow could cause that ... at least I would think it could.

That also likely means the OSB could be shot as vinyl siding needs a WRB behind it.

[Brandon Whitmore]

That also likely means the OSB could be shot as vinyl siding needs a WRB behind it.

Without a WRB, that should be pretty easy to spot. Just peek in at the joints.

[Greg Jenkins]

I pulled the joints open and peeked in behind the siding in about a dozen places and the osb was a nice pretty golden color. No stains or problems observed.