sample of the material into the pan and taking a tester
reading. It may not be possible to obtain 135 PCF dry
material In the pan, however. Any error resultant from
an inadequate compaction of the dry material will be
This curve IS accurate as long as the same 135
PCF is produced in the field. If other weights are desired
for field compaction, then a separate curve should be
produced for each desired field weight. Obviously, It is
desirable to attempt to select only one or two appropriate
field weights to minimize curves and effort
The pan can also be set on legs, anything at least two
feet from the ground and five feet from surrounding
objects Watch out for the tailgate of a pickup truck due to
the presence of the gasoline tank and spare tire, both
heavy in hydrogen.
1-32. ROOF MOISTURE TESTING
The soil tester becomes a most useful tool when it is
used to measure the trapped moisture in a built-up roof.
It is always difficult to locate a leak and to estimate the
area of roof damaged by a leak Built-up roofs generally
consist of a waterproof membrane sandwiching a thick
layer of insulation between it and the roof structure If
insulating value is damaged and the roof structure is
subject to deterioration, dry rot, or other injury.
Any attempt to puncture the roof to investigate the
degree of moisture intrusion is undesirable because of
the additional damage the testing introduces. The non-
destructive nature of the tester provides for rapid,
penetration of the roof.
All roofs are not constructed alike. They vary in
construction, and type of waterproof membrane.
Some will have hydrocarbons associated with the
construction materials and Insulation, others will have
little Internal hydrocarbon structure. The moisture
channel is affected by the internal hydrogen in the same
manner as it is with bound water in soil. Thus, a certain
background reading will be present even though the roof
A roof with wet insulation 4 inches thick will provide a
higher moisture count rate than will a roof with the same
wet insulation, but only 2-inches thick.
Thus, the reading of a moisture tester on a single
location on a roof cannot be used alone as an index of
whether the roof is wet or dry.
A series of readings over a representative sample of the
roof must be taken and readings compared to each other
to produce a profile which can then be interpreted as a
Starting from a corner, take readings on a 10 grid
pattern over the roof. 1/2 minute readings should be
quite adequate. Record the actual counts Do not bother
with computing a ratio and do not attempt to use the soil
It will be noted that a majority of the readings will fall at
some minimum value for this particular roof This will
correspond to the dry readings. Other readings will be
higher. The highest readings should be further explored
with additional readings taken on 5 grid to establish the
boundaries of the higher readings.
These highest readings represent the wettest portion of
the roof It may be necessary to make a test penetration
to determine the actual moisture present at this highest
value By observation this can be classified as an
arbitrary "moist", "wet", or "saturated" value.
Readings in between the dry bottom readings and the
moist high readings can be classified proportionately.
Extra readings should be taken around chimneys, vents,
stairwells, cornices, and other protuberances. Wet areas
should be tracked to their perimeters.
1-35. PLOT ROOF MOISTURE PROFILE
On a drawing of the roof, plot the observed values