It s not uncommon for wasp nests to restrict vent screens or for the plywood sheathing at the ridge to not be cut back sufficiently to allow the upper ridge vent to perform its intended purpose.
Black on underside of roof sheathing.
When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black.
Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest.
In our roof interior attic photo at left you can see antique roof framing along with black stains and probably some mold growth from a long history of roof leaks.
The roof was supposedly replaced two years ago.
These are commonly seen underneath roof vents plumbing stacks vent hoods and around chimneys.
This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate.
Does mold on attic sheathing have to be removed.
Mold growing on the sheathing in your attic is a serious problem that shouldn t be ignored.
Dark areas on the underside of roof sheathing can sometimes be tricky to diagnose.
Seeing some stains on the underside of the roof sheathing or framing may not be a cause for serious concern.
Roof leakage can often be seen as dark black stains concentrated and radiating out from one or more individual locations.
This can be caused by the action of fungal growth and molds and the affect they have on the tannins in the wood.
The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black.
The presence of mold inside your home even if it.
Check other attic vents if present e g.
Mold on the underside of roof sheathing is also very common.
Mold that grows on the underside of roof sheathing due to ideal mold growth conditions being present.
Mold on attic sheathing.
Wood will discolor when dampened on a regular basis.
Ridge vents roof vents gable vents and make sure they re unrestricted and properly installed.
In the vast majority of cases the mold growth is caused by condensation.
The east gable wall is black the west gable wall is fine.