Black On Underside Of Roof

Mold that grows on the underside of roof sheathing due to ideal mold growth conditions being present.

Black on underside of roof.

Picture a cloud of moisture floating overhead between the rafters. Black mold growth on the underside of your roof and ceiling can be extremely common in some areas. The roof has baffles at alternating thusses soffit and ridge vents. Mold requires a few key elements in order to grow and thrive.

Essentially condensation occurs at night when the temperature inside a building is warmer than outside. In the vast majority of cases the mold growth is caused by condensation. 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.

Skips a few trusses and reappears on the next panel or two. Mold usually causes a musty odor and may cause staining that may be black brown gray white yellow or green. These are commonly seen underneath roof vents plumbing stacks vent hoods. After several years of this there may be.

The mold itself may have a cottony texture but can also be velvety leathery or. Organic materials to feed off moisture warmth and darkness. That excess moisture ends up as drops of condensation on the roof. This can be caused by the action of fungal growth and molds and the affect they have on the tannins in the wood.

Warm wet air rises and meets the cold roof and cools. The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black. At the south end of the roof the ridge changes direction causing an overlay condition. 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.

A 10 x 10 area of plywood has been removed to provide air into this area. This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. The black mold is on the first 3 truss panels.