1、Designation: D7954/D7954M 14Standard Practice forMoisture Surveying of Roofing and Waterproofing SystemsUsing Non-Destructive Electrical Impedance Scanners1This standard is issued under the fixed designation D7954/D7954M; the number immediately following the designation indicates theyear of original
2、 adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice applies to techniques that use non-destructive electr
3、ical impedance (EI) scanners to locate mois-ture and evaluate the comparitive moisture content withininsulated low-slope roofing and waterproofing systems.1.2 This practice is applicable to roofing and waterproofingsystems wherein insulation is placed above the deck andpositioned underneath and in c
4、ontact with electrically noncon-ductive single-ply or built-up roofing and waterproofing mem-branes and systems such as coal tar, asphalt, modified bitumen,thermoplastics, spray polyurethane foam, and similar electri-cally nonconductive membrane materials. This practice is alsoapplicable to roofing
5、and waterproofing systems without insu-lation placed above moisture absorbing decks such as wood,concrete, or gypsum, that are in contact with single-ply orbuilt-up roofing and waterproofing membranes as describedabove.1.3 This practice is applicable to roofing and waterproofingsystems incorporating
6、 electrically nonconductive rigid boardinsulation made from materials such as organic fibers, perlite,cork, fiberglass, wood-fiber, polyisocyanurate, polystyrene,phenolic foam, composite boards, gypsum substrate boards,and other electrically nonconductive roofing and waterproofingsystems such as spr
7、ay-applied polyurethane foam.1.4 This practice is not appropriate for all combinations ofmaterials used in roofing and waterproofing systems.1.4.1 Metal and other electrically conductive surface cover-ings and near-surface embedded metallic components are notsuitable for surveying with impedance sca
8、nners because of theelectrical conductivity of these materials.1.4.2 This practice is not appropriate for use with BlackEPDM membranes or coatings because of its high dielectriccontent and will give false positives.1.4.3 Aluminum foil on top-faced insulation, roofing, orwaterproofing membranes gives
9、 a false positive reading and isnot suitable for surveying with impedance scanners; however,liquid-applied aluminum pigmented emulsified asphalt-basedcoatings shall not normally affect impedance scanner readings.1.4.4 See A1.4 for some cautionary notes on roofing anoma-lies and limitations that affe
10、ct the impedance test practice.1.5 Moisture scanners using impedance based technologyare classified as EI scanners.NOTE 1The term capacitance is sometimes used when describingimpedance scanners. Capacitance scanners are purely capacitive as theydo not have a resistive component. Impedance scanners c
11、ombine bothcapacitance and resistance for testing; thus, they are well suited to themeasurement of different types of materials and constructions found inroofing and waterproofing systems as the combination of both componentsallows for a more versatile testing, calibration, and measurement arrange-m
12、ent.1.6 This practice also addresses necessary verification ofimpedance data involving invasive test procedures using coresamples.1.7 This practice addresses two generally accepted scanningtechniques for conducting moisture surveys using electricalimpedance scanners:1.7.1 Technique AContinuous syste
13、matic scanning andrecording (see 8.2), and1.7.2 Technique BGrid format scanning and recording(see 8.3).1.8 This practice addresses some meteorological conditionsand limitations for performing impedance inspections.1.9 This practice addresses the effect of the roofing orwaterproofing construction, ma
14、terial differences, and exteriorsurface conditions on the moisture inspections.1.10 This practice addresses operating procedures, operatorqualifications, operating methods, scanning, surveying, andrecording techniques.1.11 UnitsThe values stated in either SI units or inch-pound units are to be regar
15、ded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in non-conformance with the standard.1.12 This standard does not purport to address all of thesafe
16、ty concerns, if any, associated with its use. It is the1This practice is under the jurisdiction ofASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.20 on RoofingMembrane Systems.Current edition approved July 15, 2014. Published August 2014. DOI: 10.1
17、520/D7954_D7954M-14.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to
18、use. Caution should betaken when accessing, walking, or using scanning equipmenton the roofing or waterproofing surfaces, or elevated locations,when using ladders, and when raising and lowering equipmentto elevated locations.2. Referenced Documents2.1 ASTM Standards:2C1616 Test Method for Determinin
19、g the Moisture Contentof Organic and Inorganic Insulation Materials by WeightD1079 Terminology Relating to Roofing and WaterproofingD7438 Practice for Field Calibration and Application ofHand-Held Moisture MetersE2586 Practice for Calculating and Using Basic StatisticsF2659 Guide for Preliminary Eva
20、luation of ComparativeMoisture Condition of Concrete, Gypsum Cement andOther Floor Slabs and Screeds Using a Non-DestructiveElectronic Moisture MeterNOTE 2See A1.3 for other referenced documents.3. Terminology3.1 For definitions of terms used in this practice, refer toTerminology D1079.3.2 Definitio
21、ns of Terms Specific to This Standard:3.2.1 comparative moisture, content, nqualitative charac-terization of moisture content in relative terms (that is, low,medium, and high levels of moisture).3.2.2 core sample, nsmall specimen of insulation andmembrane having a minimum of 2-in. 50-mm diameterobta
22、ined by cutting through these components down to thedeck and removing them from the roofing section under test.3.2.2.1 DiscussionCore samples are used to verify themembrane and insulation composition and ascertain informa-tion on their condition.3.2.3 detect or detection, v or nfor the purpose of im
23、ped-ance scanning, the condition at which there is a consistentindication that an elevated level of impedance reading ispresent within the roofing or waterproofing system.3.2.4 false-positive, adjreading that indicates that elevatedmoisture is present when it is not.3.2.4.1 DiscussionFor example, a
24、false positive in roofingfor impedance scanning may be returned when some otherelectrically conductive material is present in the roofingsystem.3.2.5 gravimetric analysis, ndetermination of moisturecontent by weight of a material by comparing wet weight toover dry weight expressed as a percentage.3.
25、2.6 moisture content, MC, nmass of moisture per unitmass of dry material.3.2.6.1 DiscussionThe moisture content is usually ex-pressed as a percentage by weight and determined gravimetri-cally.3.2.7 roof assembly, nassembly of interacting roof com-ponents including the roof deck, air or vapor retarde
26、r, insula-tion and membrane, or primary roof covering designed toweatherproof a structure.3.2.8 roof section, nportion of a roof that is separatedfrom adjacent portions by walls or expansion joints with nochanges in the components throughout the section.4. Summary of Practice4.1 This practice covers
27、 a procedure in which a specificallydeveloped non-destructive electronic impedance (EI) basedmoisture scanner is used in conjunction with interpretive dataand invasive verification practices to detect and evaluate themoisture conditions within low-sloped roofing and waterproof-ing systems by non-des
28、tructively measuring the electricalalternating current (ac) impedance.4.2 This practice is intended to be used in conjunction withthe impedance scanner manufacturers operation instructionsand guides.5. Significance and Use5.1 Excess moisture trapped in roofing or waterproofingsystems can adversely a
29、ffect performance and lead to prema-ture failure of roofing or waterproofing systems and itscomponents. It also reduces thermal resistance, resulting inreduced energy efficiency and inflated energy costs. Impedancescans can be effective in identifying concealed and entrappedmoisture within roofing o
30、r waterproofing systems.5.2 This practice is intended to be used at various stages ofthe roofing and waterproofing systems life such as: during orat completion of installation of roofing system to determine ifthere was moisture intrusion into the roofing system ormaterials for quality control purpos
31、es, at regular intervals aspart of a preventative maintenance program, and before re-roofing or repair work to assist in determining the extent ofwork and replacement materials.5.3 This practice alone does not determine the cause ofmoisture infiltration into roofing or waterproofing systems;however,
32、 it can be used to help tracing excess moisture to thepoint of ingress.6. Apparatus6.1 EI ScannerThis apparatus shall be specifically devel-oped to detect and evaluate non-destructively comparativemoisture conditions within roofing and waterproofing systems.6.1.1 Principles of OperationThe EI of a m
33、aterial variesin proportion with the materials moisture content. The EI ofmaterials such as those listed in 1.2 and 1.3 in the roofing orwaterproofing system directly under the footprint of the scan-ner is measured by creating an alternating electric field thatpenetrates the materials under test. Th
34、e small alternatingcurrent (ac) flowing through this field is inversely proportionalwith the impedance of these moisture-absorbing materials. The2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
35、volume information, refer to the standards Document Summary page onthe ASTM website.D7954/D7954M 142instrument determines the currents amplitude and converts thisvalue to a comparative moisture value.6.1.1.1 The depth of the signal penetration varies dependingon the sensitivity and signal strength s
36、ettings of the scanner aswell as the composition of materials, thickness, and moisturecontent of the roofing or waterproofing system under test.6.1.2 Apparatus Requirements:6.1.2.1 The moisture scanner shall be capable of sendingsignals non-destructively into the materials below the surfacingand the
37、 scanner.6.1.2.2 The moisture scanner shall have integrate adjustablecalibration ability for the differing composition, thickness,density of materials, and moisture conditions that can beencountered in roofing or waterproofing assemblies.6.1.2.3 The moisture scanner shall have a display givingcompar
38、ative readings of moisture conditions of materials foundin roofing and waterproofing systems.6.2 Scanner TypesTwo types of impedance scanners arecommercially available:6.2.1 Handheld scanner designed to be used for pointreadings on a grid system, and6.2.2 Mobile-wheeled scanner, which can be rolled
39、acrossthe roofing or waterproofing to obtain continuous readings asthe scanner moves over the surface.NOTE 3See A1.1 and A1.2 for examples of typical handheld andmobile-wheeled types of impedance scanners.7. Operator Qualifications and Referenced Materials7.1 The operator shall:7.1.1 Be familiar wit
40、h the use of the impedance scanner;7.1.2 Have knowledge of and available for reference at theroof site a copy of the manufacturers operating and calibrationinstructions for the impedance scanner used;7.1.3 Have knowledge of how and under what circum-stances the impedance scanning system can be used,
41、 as well asits limitations;7.1.4 Have a thorough understanding of the constructionand components used in the roofing or waterproofing systemassembly under test, such as types of membranes, roofinginsulations, decking, and attachment;7.1.5 Confirm the composition of the roofing or waterproof-ing asse
42、mbly and endeavor to obtain historical data regardingthe construction, age, and performance of the roofing orwaterproofing assembly; and7.1.6 Have a thorough understanding and knowledge ofroofing and waterproofing technology including types of roof-ing or waterproofing membranes and materials, decks
43、, insula-tion materials, system assemblies and construction procedures,equilibrium moisture content, moisture migration in buildings,as well as health and safety requirements when carrying outroofing or waterproofing moisture surveying.7.2 Data InterpreterIndividuals interpreting the field datashall
44、 have knowledge of: impedance scanner principles ofFIG. 1 Typical Non-Destructive Moisture ScannerD7954/D7954M 143operation, moisture migration transport mechanisms, environ-mental effects, oven dry and equilibrium moisture contents(EMC), thermal resistance ratios (TRR), verification methods,and roo
45、fing and waterproofing construction as it applies tomoisture analysis and gravimetric analysis to diagnose andinterpret the readings from the roofing or waterproofing systemsurveyed.NOTE 4See A1.4 for additional information on technique and anoma-lies.8. Impedance Scanning Techniques8.1 Two techniqu
46、es, (A) and (B), for conducting moisturesurvey susing impedance scanners are:8.2 Technique AContinuous Systematic Scanning andRecordingThis practice involves moving (rolling) the imped-ance scanner in a systematic and continuous row-by-rowmanner when traversing the roof surface.8.2.1 As the scanner
47、is rolled along each run or row in asystematic fashion, continuous impedance readings shall bedisplayed on the scanners meter. These readings shall bevisually observed by the operator.8.2.2 All areas where elevated moisture content levels areindicated by increased impedance readings displayed on the
48、scanners meter shall be referenced, recorded, and marked onthe roof surface or the appropriate position on the roof drawingor both by the operator.8.2.3 This technique is applicable to the mobile-wheeledunit as it gives a continuous reading while traversing the roofsurface (see 6.2.2).8.3 Technique
49、BGrid Format Scanning and RecordingThis practice involves the scanning the roof using a grid formatwhere the scanner is moved within the grid pattern.8.3.1 Scanning is done with a grid pattern layout system inwhich the scanner is moved in a uniform fashion within thegrid pattern. Readings are taken and recorded at each gridintersection point or at regular similar spaced intervals on orbetween grid lines; additional readings are taken and recordedin areas where elevated moisture levels are indicated byincreased impedance readings.8.3.2 See 9.3 for i
