Black On Underside Of Roof

A 10 x 10 area of plywood has been removed to provide air into this area.

Black on underside of roof.

Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest. Warm wet air rises and meets the cold roof and cools. In the vast majority of cases the mold growth is caused by condensation. Mold usually causes a musty odor and may cause staining that may be black brown gray white yellow or green.

Picture a cloud of moisture floating overhead between the rafters. The black mold is on the first 3 truss panels. After several years of this there may be. This can be a problem for many homeowners and needs to be addressed as soon as it is found to avoid the consequences it can bring.

When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black. That excess moisture ends up as drops of condensation on the roof. Black mold growth on the underside of your roof and ceiling can be extremely common in some areas. This can be caused by the action of fungal growth and molds and the affect they have on the tannins in the wood.

This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. The roof has baffles at alternating thusses soffit and ridge vents. The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black. Skips a few trusses and reappears on the next panel or two.

Organic materials to feed off moisture warmth and darkness. This latter phenomenon occurs when the house is too humid and the warm moist air seeps into the attic where it condenses and freezes on cold attic areas. Essentially condensation occurs at night when the temperature inside a building is warmer than outside. These are commonly seen underneath roof vents plumbing stacks vent hoods.

Mold that grows on the underside of roof sheathing due to ideal mold growth conditions being present. At the south end of the roof the ridge changes direction causing an overlay condition. Roof leakage can often be seen as dark black stains concentrated and radiating out from one or more individual locations.