Underside Of Roof Sheathing Is Wet

When this phenomenon occurs the sheathing or framing may become slightly wet on the surface.

Underside of roof sheathing is wet.

The sheathing at the peak of the roof was saturated with moisture. Does mold on attic sheathing have to be removed. The following picture is of a long standing moisture condition in an attic where much of the roof sheathing has turned black. Mold on attic sheathing.

When moisture condenses on plywood roof sheathing repeatedly or continuously the wood will turn black. Mold growth provided it is not just cosmetic mold which can simply be left alone can be cleaned from wood surfaces by blasting scrubbing or even simple surface wiping depending on the surface accessibility and. Those often are the underside of 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.

In the vast majority of cases the mold growth is caused by condensation. There were also several issues with the intersection of the roofs where the 2 apartments meet. On going back inside the attic the frost had melted and the underside of the sheathing was wet not so much that it was dripping but enough that it was damp. Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest.

The osb and in fact any wood panels must be allowed to dry completely depending on how wet the panels are this could be a few days before any roofing material is applied to avoid trapping moisture under the roof material that could cause edge swell and buckling. The ventilation is needed not only for moisture control but also to reduce by 20 40 high summertime attic and roof sheathing temperatures which are bad for roof trusses rafters and the roof sheathing as well as the shingles and underlying waterproofing membrane which can reach 160 180 degrees over an unventilated attic. This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. Installation tips osb roof sheathing the ol sage builder trubord.

Trapped water will boil when the sun heats the roof and the shingles will then have small pits where. It is never a good idea to install a roof over wet plywood or any type of roof sheathing. If the temperature drops below the freezing point often at night after the sun goes down this moisture will freeze.