1、Designation: D7954/D7954M 15Standard 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 non-conductive 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 incorporatin
6、g 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 sp
7、ray-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 sc
8、anners because of theelectrical conductivity of these materials.1.4.2 Black ethylene propylene diene terpolymer (EPDM)produces false positive readings when tested because of thematerials high dielectric constant.1.4.3 Aluminum foil on top-faced insulation, roofing, orwaterproofing membranes gives a
9、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 affect
10、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 comb
11、ine 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-ment
12、.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 systemat
13、ic 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, mater
14、ial 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 regarded
15、 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 thesafety
16、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 Feb. 15, 2015. Published March 2015. Originallyapp
17、roved in 2014. Last previous edition approved in 2014 as D7954/D7954M 14.DOI: 10.1520/D7954_D7954M-15.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 hea
18、lth practices and determine the applica-bility of regulatory limitations prior to 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 loc
19、ations.2. Referenced Documents2.1 ASTM Standards:2C1616 Test Method for Determining 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
20、Practice for Calculating and Using Basic StatisticsF2659 Guide for Preliminary Evaluation 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 d
21、efinitions of terms used in this practice, refer toTerminology D1079.3.2 Definitions 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, nsma
22、ll specimen of insulation andmembrane having a minimum of 2-in. 50-mm diameterobtained 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 info
23、rma-tion on their condition.3.2.3 detect or detection, v or nfor the purpose of imped-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
24、 that elevatedmoisture is present when it is not.3.2.4.1 DiscussionFor example, a 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
25、 a material by comparing wet weight toover dry weight expressed as a percentage.3.2.6 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, nasse
26、mbly of interacting roof com-ponents including the roof deck, air or vapor retarder, 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 th
27、e components throughout the section.4. Summary of Practice4.1 This practice covers 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 them
28、oisture conditions within low-sloped roofing and waterproof-ing systems by non-destructively 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
29、 Use5.1 Excess moisture trapped in roofing or waterproofingsystems can adversely affect 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. Impedancescan
30、s can be effective in identifying concealed and entrappedmoisture within roofing or waterproofing systems.5.2 This practice is intended to be used at various stages ofthe roofing and waterproofing systems life such as: completionof installation of roofing system to determine if there wasmoisture int
31、rusion into the roofing system or materials forquality control purposes, at regular intervals as part of apreventative maintenance program, and before re-roofing orrepair work to assist in determining the extent of work andreplacement materials.5.3 This practice alone does not determine the cause of
32、moisture infiltration into roofing or waterproofing systems;however, 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
33、and waterproofing systems.6.1.1 Principles of OperationThe EI of a material 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 al
34、ternating electric field thatpenetrates the materials under test. The 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 Cu
35、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.D7954/D7954M 152instrument determines the currents amplitude and converts thisvalue to a comparative moisture value.6.1.1.1 The depth of the signal
36、penetration varies dependingon the sensitivity and signal strength settings 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 sendingsig
37、nals non-destructively into the materials below the surfacingand the scanner.6.1.2.2 The moisture scanner shall have integrated adjust-able calibration ability for the differing composition, thickness,density of materials, and moisture conditions that can beencountered in roofing or waterproofing as
38、semblies.6.1.2.3 The moisture scanner shall have a display givingcomparative 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
39、on a grid system, and6.2.2 Mobile-wheeled scanner, which can be rolled 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 Qualificatio
40、ns and Referenced Materials7.1 The operator shall:7.1.1 Be familiar with 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 a
41、nd under what circum-stances the impedance scanning system can be used, 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 attachm
42、ent;7.1.5 Confirm the composition of the roofing or waterproof-ing assembly 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 incl
43、uding types of roof-ing or waterproofing membranes and materials, decks, 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 sur
44、veying.7.2 Data InterpreterIndividuals interpreting the field datashall have knowledge of: impedance scanner principles ofFIG. 1 Typical Non-Destructive Moisture ScannerD7954/D7954M 153operation, moisture migration transport mechanisms, environ-mental effects, oven dry and equilibrium moisture conte
45、nts(EMC), thermal resistance ratios (TRR), verification methods,and roofing 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 te
46、chnique and anoma-lies.8. Impedance Scanning Techniques8.1 Two techniques, (A) and (B), for conducting moisturesurveys using impedance scanners are:8.2 Technique AContinuous Systematic Scanning andRecordingThis practice involves moving (rolling) the imped-ance scanner in a systematic and continuous
47、row-by-rowmanner when traversing the roof surface.8.2.1 As the scanner 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 conte
48、nt levels areindicated by increased impedance readings displayed on thescanners 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 continu
49、ous reading while traversing the roofsurface (see 6.2.2).8.3 Technique 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 moistu
