Attic Sheathing Black

White and green fuzzy growth on osb sheathing.

Attic sheathing black.

Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest. The mold itself may have a cottony texture but can also be velvety leathery or. Despite what your roofer would like you to believe roof leaks rarely cause significant mold problems. When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black.

This can be caused by the action of fungal growth and molds and the affect they have on the tannins in the wood. In many cases the continued wetting of the sheathing will cause it to rot but that may take several years or decades depending on the attic ventilation. Mold usually causes a musty odor and may cause staining that may be black brown gray white yellow or green. If the wood is soft if it s easily imprinted when you push on it it s probably rotten.

In old houses you ll usually see some spots that are stained dark or black where there was a roof leak at some point in time which was repaired but the stain remains. Attic mold cleaner attic mold removal how to clean attic mold how attic mold gets there in the first place and what to do to help prevent attic mold. I have surface mold on the sheathing in my 1982 vintage 12 6 pitched attic. Uniform black mold growth on attic sheathing.

Condensation determining the cause of attic mold. The other two possibilities for the stains. Even in this case in our opinion the reasons to remove and replace roof sheathing and framing would normally be based on the condition of the roof framing and sheathing not on the presence of mold or stains. This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate.

The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black. 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.