7
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:
Drive the contact pins
into the plaster to their full penetration, if possible.
Press read button
and read the reference scale
.
Taking a Reading Below the Surface:
Drive a pair of nails into the plaster
at least
⅓ of the total thickness of the plaster. If you are applying plaster to a
material of doubtful dryness, such as brick or concrete, drive the nails through the plaster and into the brick or concrete.
Touch 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:
Drive 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
Apply the other pin to various parts of the wall
where you suspect the leak originates. If the meter indicates red or
“wet”, the material is wet between the points of contact. If the meter reads green or “dry”, the material along this line is not
in the path of a leak.
To confirm if a brick wall is waterproof:
Perform the following procedure after storms to verify if a brick wall is waterproof, or if waterproofing repairs have been properly
performed:
Drive pairs of nails into the brick
wherever it is necessary to make the tests and leave them in place until after all the
tests are completed.
Take readings after each storm,
and record the readings. The pattern of these readings will indicate if the brick is
gradually drying out or is moistened again by each storm.
Summary of Contents for BD-10
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