This can be caused by the action of fungal growth and molds and the affect they have on the tannins in the wood.
Black on sheathing in attic.
I m aware of the cause poorly vented bathroom fans and not well sealed fan fixtures lights wires etc.
When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black.
This summer i cleaned the portion of the black stain with a dry mop as much as i could reach from the hatch opening.
Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest.
If your attic sheathing doesn t look like new construction and is visibly black or white stained like this picture you likely have a ventilation issue that needs to be addressed and mold remediated.
Something else you can do to help is get.
Mold growing on the sheathing in your attic is a serious problem that shouldn t be ignored.
While the black stains are either mould or just black dust from attic insulation settled on the.
In the vast majority of cases the mold growth is caused by condensation.
The mold is likely coming from a condensation buildup along your soffet a good trick would be to get in there and attach cut foam blocks at the top of your wall cavity up to the roof deck to seal the soffet of from the attic space wherever cooler and warmer air mix there will be condensation.
Black or white staining in attic.
Last winter i took a look into the attic and noticed black stains and water marks on a portion of the sheathing material.
In the attic photograph at left we show a mix of green gray and white attic mold.
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.
I have surface mold on the sheathing in my 1982 vintage 12 6 pitched attic.
Mold on attic sheathing.
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.
The photo at page top shows white attic mold on the roof sheathing and rafters and some brown or black mold on the attic side of ceiling drywall where we pulled back insulation.