Delmhorst Instrument BD-10 - Manual (Page 10)

Testing Plaster Walls, Sheetrock (Gypsum)
Under normal drying conditions and proper application of plaster
(sufficient drying time between coats), surface readings give accurate
results. However, if rapid drying occurs, the surface of the plaster
may be dry, but moisture is still present below the surface and will
eventually affect the paint or wallpaper. This condition occurs when
there is high temperature or exceptionally good air circulation, or
where brown scratch and white coats are applied within a few days.
Take several readings on each wall. Pay special attention near the
base, around doorjambs, electrical and plumbing fixtures, and other
places where the plaster is thicker than normal.
Taking a Surface Reading:
hDrive the contact pins
%
into the plaster to their full
penetration, if possible.
hPress read button
!
and read the reference scale
$
.
Taking a Reading Below the Surface:
hDrive a pair of nails into the plaster at least 1/3 of the
total thickness of the plaster. If you are applying plaster
to a material of doubtful dryness, such as brick or con-
crete, drive the nails through the plaster and into the
brick or concrete.
hTouch the heads of the nails with the contact pins
%
and read
the meter.
The following guidelines may be used to interpret the meter readings
on plaster or sheetrock prior to painting or applying adhesives:
Green or “dry” — < 4% moisture
Red or “wet” — approximately 5%
Yellow — Borderline
Tracing Leaks
The BD-10 can help trace leaks in masonry material. Normally, dry
plaster, brick, or concrete will contain so little moisture it cannot be
detected by the meter. If the meter indicates the presence of moisture
you can trace the moisture to its origin.
To trace the origin of a leak:
hDrive a nail into an area that is known to be wet and attach an
insulated wire between the nail and one of the contact pins
%
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