Delmhorst Instrument TechCheck PLUS - Manual (Page 10)

Copyright  2009, Delmhorst Instrument Co.
Page 10 of 33
meter’s PIN mode will give relative readings only, not %MC. The numbers displayed
represent the relative dryness or wetness of the material on a scale of 5 to 60. In order to
accurately interpret your readings, first establish a baseline reading by taking a reading in an
area you know to be unaffected, then take a reading in the affected area and compare the
two readings.
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 further 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:
USING PIN MODE
Ø Drive two hardened-steel masonry nails about 3/4" apart into the finish coat of
concrete floor. Drive them about 1/8" deep so they make firm contact with the concrete
and do not move when touched.
Ø Touch the nails with the contact pins. Remember that when used on materials other
than wood, the meter’s PIN mode will give relative readings only. Establish a baseline
reading by taking a reading in an area you know to be unaffected, then take a reading in
the affected area and compare the two readings.
USING SCAN MODE
Ø First establish a benchmark. Take readings in areas that you know are dry, or
acceptable.
Ø Take readings on areas that are wet. These “dry to wet” readings can be used as
reference points against which subsequent readings are compared. Understanding the
meter’s behavior on a particular material, along with these comparative readings, your
experience, and visual clues will all help determine the overall condition. All readings
should be evaluated in the light of factors such as type of paint, type of construction, and
climatic conditions.
Subsurface test:
Ø Drill two 1/4" holes, 3/4" apart and 1/2" to 2" deep.
Ø Drive the masonry nails into the bottom of the holes and make the tests as described
above. Nails must not touch sides of drilled holes.