Delmhorst Instrument BD-10 - Manual (Page 9)

Testing Brick or Concrete for Paint Application
Brick, stucco, or concrete surfaces must be dry at the time of
application and must remain dry after paint is applied or failure
of the paint film may occur. These materials are frequently
exposed to unusual moisture conditions that allow them to absorb
moisture through some exposed surface or some structural defect.
This is why it is important to check the moisture content of the
brick or concrete when it has been exposed to conditions that
permit it to absorb moisture.
Procedure:
hDrive two hardened steel masonry nails about 3/4” apart into
the brick or concrete. Drive them about 1/4” deep so they
make firm contact and do not move when touched.
hTouch the nails with the contact pins
%
.
hPress read button
!
and read the reference scale
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.
Normally, dry concrete or brick will read in the green or “dry”
portion of scale, indicating a safe condition to apply paint.
Meter readings should be evaluated in relation to other factors —
knowledge of the structure, type of paint used, expected weather
conditions in the near future, etc. Paint should not be applied if
readings are in the red or “wet” portion of the scale.
Do not be misled by surface appearance of masonry materials.
Short exposure to rain may thoroughly wet the surface while
the interior is still dry. In this instance, we recommend repeating
the test on the masonry
below the surface as mentioned above.
Key Areas to Check:
hThe rear side of brick parapet walls — generally are not
waterproof above the flashing line and frequently absorb
moisture during rains.
hPainted concrete floors on ground — subject to peeling as
they absorb moisture from the earth, unless an effective
vapor barrier has been installed.
Tests on these materials should be made a day or so after they
have been exposed to rain or other high moisture conditions to
verify to what extent they absorb moisture.
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