What causes this?

[Jim Hintz]

31497

House is only two years old, I suspect it's on the north side of the house and possibly related to a bit of heat loss? Is it a form of mold or just crud?

Thanks Everybody -
Jim

[Lon Henderson]

Hard to tell scale or context in your photo. A three holer in the out house?

But seriously folks, can you give us a little more info?

[Raymond Wand]

Lon

I believe its a soffit vent with some sort of algae growth.

[stanley frost]

Looks like soffit vents that are not working properly. They appear to be working as an exhaust vent as opposed to intake vents. Warm air is flowing out and causing condensation to form on the soffit material. My bet is that the attic ventilation is not properly balanced/working.

- - - Updated - - -

Looks like soffit vents that are not working properly. They appear to be working as an exhaust vent as opposed to intake vents. Warm air is flowing out and causing condensation to form on the soffit material. My bet is that the attic ventilation is not properly balanced/working.

[Vern Heiler]

My guess is, that was a piece of scrap that had been laying in the wet dirt and used as blocking. Painters slapped a coat of paint on and not long after the crud came through.

[Jerry Peck]

Looks like soffit vents that are not working properly. They appear to be working as an exhaust vent as opposed to intake vents. Warm air is flowing out and causing condensation to form on the soffit material. My bet is that the attic ventilation is not properly balanced/working.

Soffit vents, when only soffit vents are installed, as is the case in many Florida houses, especially in South Florida where high wind events would blow ridge vents off, function as both intake and exhaust for the attic ventilation ... the function of intake or exhaust depends on which way the wind is blowing and which side of the roof has high pressure (intake) and which side has low pressure (exhaust/discharge).

With ridge vents or off ridge vents, the soffit vents are primarily intended to serve as intakes for the attic ventilation in that the air enters the soffit vents at the eaves and exits the ridge/off ridge vents higher up.

[Lon Henderson]

Lon

I believe its a soffit vent with some sort of algae growth.

Rarely see that here. My guess is some sort of crud not associated with its current location. If humid air was exiting those vents to promote mold, I would expect to see mold on the soffit above them.

[Ian Page]

Damp/ wet wood painted over with latex paint. Seen that kind of thing many times while house painting. If just around one hole, access egress for insects (wasps, bees etc) or rodents. Wipe off, prime/seal and reapply top coat.

[John Kogel]

If it's only in the one rafter bay, which the one pic doesn't tell us BTW ;), my guess is, what Raymond said, there is an exhaust vent pipe shoved into the soffit.

And yes, in the Pacific NW, warm moist air promotes that kind of algae or mould to grow.

I have a pic of one of those holes that has a dirt smear around it. That was definitely a rat hole. They were clawing their way right up the side of the house, 10 feet to the hole.