TM 5-6635-386-12&Psample of the material into the pan and taking a testerreading. It may not be possible to obtain 135 PCF drymaterial In the pan, however. Any error resultant froman inadequate compaction of the dry material will benegligible.h.This curve IS accurate as long as the same 135PCF is produced in the field. If other weights are desiredfor field compaction, then a separate curve should beproduced for each desired field weight. Obviously, It isdesirable to attempt to select only one or two appropriatefield weights to minimize curves and effortThe pan can also be set on legs, anything at least twofeet from the ground and five feet from surroundingobjects Watch out for the tailgate of a pickup truck due tothe presence of the gasoline tank and spare tire, bothheavy in hydrogen.1-32. ROOF MOISTURE TESTINGThe soil tester becomes a most useful tool when it isused to measure the trapped moisture in a built-up roof.It is always difficult to locate a leak and to estimate thearea of roof damaged by a leak Built-up roofs generallyconsist of a waterproof membrane sandwiching a thicklayer of insulation between it and the roof structure Ifmoisture becomes trapped In the insulation, theinsulating value is damaged and the roof structure issubject to deterioration, dry rot, or other injury.Any attempt to puncture the roof to investigate thedegree of moisture intrusion is undesirable because ofthe additional damage the testing introduces. The non-destructive nature of the tester provides for rapid,accurate determination of roof moisture withoutpenetration of the roof.1-33. ROOF MOISTURE IS A RELATIVEMEASUREMENTAll roofs are not constructed alike. They vary inthickness, type of insulation, type of underlyingconstruction, and type of waterproof membrane.Some will have hydrocarbons associated with theconstruction materials and Insulation, others will havelittle Internal hydrocarbon structure. The moisturechannel is affected by the internal hydrogen in the samemanner as it is with bound water in soil. Thus, a certainbackground reading will be present even though the roofis "dry".A roof with wet insulation 4 inches thick will provide ahigher moisture count rate than will a roof with the samewet insulation, but only 2-inches thick.Thus, the reading of a moisture tester on a singlelocation on a roof cannot be used alone as an index ofwhether the roof is wet or dry.A series of readings over a representative sample of theroof must be taken and readings compared to each otherto produce a profile which can then be interpreted as amoisture profile.1-34. PROCEDUREStarting from a corner, take readings on a 10’ gridpattern over the roof. 1/2 minute readings should bequite adequate. Record the actual counts Do not botherwith computing a ratio and do not attempt to use the soilmoisture chart to determine actual moisture inengineering units.It will be noted that a majority of the readings will fall atsome minimum value for this particular roof This willcorrespond to the dry readings. Other readings will behigher. The highest readings should be further exploredwith additional readings taken on 5’ grid to establish theboundaries of the higher readings.These highest readings represent the wettest portion ofthe roof It may be necessary to make a test penetrationto determine the actual moisture present at this highestvalue By observation this can be classified as anarbitrary "moist", "wet", or "saturated" value.Readings in between the dry bottom readings and themoist high readings can be classified proportionately.Extra readings should be taken around chimneys, vents,stairwells, cornices, and other protuberances. Wet areasshould be tracked to their perimeters.1-35. PLOT ROOF MOISTURE PROFILEOn a drawing of the roof, plot the observed values1-22
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