Copyright
2009, Delmhorst Instrument Co.
Page 10 of 35
If you suspect a problem take a visual inspection. Look for gaps around windows, doors, air
conditioning units, light fixtures, hose bibs, dryer vents and other areas of potential penetration.
Also look for visible signs of water damage. If you feel a problem exists, use the
21-E electrode
.
This electrode uses the
608 -
(4") insulated pins or 608/001 (7”) insulated pins.
Procedure:
Drill two 1/4" holes
about ¾” apart at an upward 45° angle.
Push the 21-E Electrode into the holes
through the polystyrene and into the substrate and
read the moisture content on the meter scale. When used on materials other than wood, the
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 6 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 comparative moisture conditions in concrete slabs.
They can tell you where there may be excess moisture and help determine if you need to conduct
further testing, and identify specific areas on which that testing should be performed. Meters do
not provide quantitative results as a basis for acceptance of a slab for installation of moisture-
sensitive flooring systems. ASTM Test Method F2170 (RH using in-situ probes), F1869 (calcium
chloride), and F2420 (RH on surface using insulated hood) provide quantitative information for
determining if moisture levels are within specific limits.
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
– WOOD scale
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.
Touch the nails
with the contact pins.
If the meter reads less than “28”, the surface is
dry. However, sub-surface tests should be made to verify if the slab is dry throughout.
USING SCAN MODE
First establish a benchmark by takingreadings in areas that you know are dry, or
acceptable.
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