9
The LEDs are a visual aid to help quickly determine the moisture level that each reading
indicates. Readings that activate the green light indicate a sufficiently dry moisture level,
those that activate the yellow light indicate a borderline situation, and those that active the red
light indicates material that is too wet for most applications.
TESTING PLASTER WALLS
Under normal drying conditions and proper application of plaster (sufficient drying time
between coats), surface readings give ac curate 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 the read button (#1) and read the reference scale.
Taking a reading below the surface:
Drive a pair of nails into the plaster at least ⅓of 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.
TESTING CONCRETE SLABS FOR FLOORING APPLICATIONS
Moisture meters are an effective tool to check moisture in concrete. They can tell you where
there may be excess moisture and help determine if you need to conduct furt her testing.
It is important to test both the surface and mid-section of the slab, especially if the slab is on
or below grade. This will help determine if there is continuous moisture migration toward the
surface. If this condition exists, the moisture movement may be so slow that once it reaches
the surface, moisture evaporates and causes a “dry” reading when a surface test is made.
However, if a sub-surface test is made, the meter may read “wet” indicating the presence of
moisture. When the slab is covered and the upward movement of moisture continues,
moisture will move into a hygroscopic (wood) floor, or build-up pressure under a non-
breathing synthetic floor, causing delamination.
Taking a surface reading:
Drive two hardened-steel masonry nails about 19mm (¾”) apart into the finish
coat of concrete floor. Drive them about 3.2mm (⅛”) deep so they make firm contact
with the concrete and do not move when touched.
Touch the nails with the contact pins.
Press read button (#1) and read the scale. If the meter reads in the red or “wet”
area, it shows the floor is not satisfactory for covering. If meter reads in the green or
“dry” area, the surface is dry. However, subsurface tests should be made to verify if
the slab is dry throughout.
