Q I have vaulted ceilings in
my house in central Minnesota.
What would cause these
two stains?
Jeff Brooks, Alexandria, MN
A You almost certainly have condensation
occurring in the wall,
probably near the peak of the cathedral
ceiling. An air leak is probably allowing
moist interior air to flow into the wall
cavity, where it’s condensing and freezing
on the inside of the exterior sheathing.
During warmer periods, the ice
melts and water seeps out through joints
in the plywood sheathing, creating stains.
Remove a few siding panels near the
peak where the moisture starts. If our
hunch is correct, joints in the sheathing
will correspond with the moisture, and
the sheathing will be damp.
If the sheathing has begun to rot,
replace it. This will allow you to examine
the framing and the wall/ceiling/
roof junction to spot the problem. If
you have a small attic space above the
cathedral ceiling, adding roof vents
may help flush out moist air.
