Black Markings On Attic Sheathing

When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black.

Black markings on attic sheathing.

This happens due to trapped damp air often in the late fall or early winter. The new roof doesn t help much most of the moist air is likely coming up from below. Black mold in attics. Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest.

The variety i see most often is fuzzy green when active and goes black like that when dormant or dead. This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. In this photo of very dark mold in an attic in a wet attic mold which we found to be brown in the microscope looked black on the plywood. When this humid relatively warm air cannot escape the attic space before the temperature drops condensation can occur.

In the vast majority of cases the mold growth is caused by condensation. That is a stain caused by mold mould. If the dark surface of the wood smudges it could be mold. In other words you could easily see where most of the joists were located because those areas were darker than the rest of the white ceiling.

Inspected a house today built in 1991. If the wood is soft if it s easily imprinted when you push on it it s probably rotten. The roof had ridge vents as well as soffit vents and. Attic moisture and poor ventilation are the causes.

Mold on attic sheathing. The black attic mold shown here confirms that this attic had a serious venting and moisture problem including moisture from sources lower in the building. The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black.