"Rudy" wrote in message
...

There is no detectable moisture that comes through the walls or the
floors.
I tested this using the "tape and seal a piece of aluminum foil" trick on
the walls and the floor. After a few days, when the taped and sealed
foil
is removed there is no moisture there. Despite all of this, there is a
VERY
SLIGHT musty smell in the basement -- it is almost undetectable, but it's
there.

Check for a basement "floor drain"..often nearby the water heater. I
think they' re mandated by code so there should be one there somewhere.
There's supposed to be a trap in these drains but they need water inside
the trap to be effective. (Some are installed with a small waterline to
keep them "filled" but most are not). See (smell) if the odor is coming
from the drain. Take the screen/grille off. It may need a cleaning in
the event its been left unattended/neglected with crud in it for years as
is usually the case. It may need a rinsing and refill of the trap..water
with a little bleach has worked for me.

There is no floor drain or open sewer line/vent. In fact the sewer line
from upstairs goes out to the outside at the ceiling level of the basement.