ASTM D7954/D7954M-15a(2021)
(Practice)Standard Practice for Moisture Surveying of Roofing and Waterproofing Systems Using Nondestructive Electrical Impedance Scanners
Standard Practice for Moisture Surveying of Roofing and Waterproofing Systems Using Nondestructive Electrical Impedance Scanners
SIGNIFICANCE AND USE
5.1 Excess moisture trapped in roofing or waterproofing systems can adversely affect performance and lead to premature failure of roofing or waterproofing systems and its components. It also reduces thermal resistance, resulting in reduced energy efficiency and inflated energy costs. Impedance scans can be effective in identifying concealed and entrapped moisture within roofing or waterproofing systems.
5.2 This practice is intended to be used at various stages of the roofing and waterproofing system’s life such as: during or at completion of installation of roofing or waterproofing system to determine if there was moisture intrusion into the roofing or waterproofing system or underlying materials; at regular intervals as part of a preventative maintenance program; and to aid in condition assessment, or before replacement or repair work, or combinations thereof, to assist in determining the extent of work and replacement materials.
5.3 This practice alone does not determine the cause of moisture infiltration into roofing or waterproofing systems; however, it can be used to help tracing excess moisture to the point of ingress.
SCOPE
1.1 This practice applies to techniques that use nondestructive electrical impedance (EI) scanners to locate moisture and evaluate the comparitive moisture content within insulated low-slope roofing and waterproofing systems.
1.2 This practice is applicable to roofing and waterproofing systems wherein insulation is placed above the deck and positioned underneath and in contact with electrically nonconductive single-ply or built-up roofing and waterproofing membranes and systems such as coal tar, asphalt, modified bitumen, thermoplastics, spray polyurethane foam, and similar electrically nonconductive membrane materials. This practice is also applicable to roofing and waterproofing systems without insulation placed above moisture absorbing decks such as wood, concrete, or gypsum, that are in contact with single-ply or built-up roofing and waterproofing membranes as described above.
1.3 This practice is applicable to roofing and waterproofing systems incorporating electrically nonconductive rigid board insulation 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 waterproofing systems such as spray-applied polyurethane foam.
1.4 This practice is not appropriate for all combinations of materials used in roofing and waterproofing systems.
1.4.1 Metal and other electrically conductive surface coverings and near-surface embedded metallic components are not suitable for surveying with impedance scanners because of the electrical conductivity of these materials.
1.4.2 This practice is not appropriate for use with black EPDM, any membranes containing black EPDM, or black EPDM coatings because black EPDM gives false positive readings.
1.4.3 Aluminum foil on top-faced insulation, roofing, or waterproofing membranes gives a false positive reading and is not suitable for surveying with impedance scanners; however, liquid-applied aluminum pigmented emulsified asphalt-based coatings shall not normally affect impedance scanner readings.
1.4.4 See A1.4 for some cautionary notes on roofing anomalies and limitations that affect the impedance test practice.
1.5 Moisture scanners using impedance-based technology are classified as EI scanners.
Note 1: The term capacitance is sometimes used when describing impedance scanners. Capacitance scanners are purely capacitive as they do not have a resistive component. Impedance scanners combine both capacitance and resistance for testing; thus, they are well suited to the measurement of different types of materials and constructions found in roofing and waterproofing systems as the combination of both components allows for a more versatile testin...
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Designation:D7954/D7954M −15a (Reapproved 2021)
Standard Practice for
Moisture Surveying of Roofing and Waterproofing Systems
Using Nondestructive Electrical Impedance Scanners
This standard is issued under the fixed designation D7954/D7954M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.4.3 Aluminum foil on top-faced insulation, roofing, or
waterproofing membranes gives a false positive reading and is
1.1 This practice applies to techniques that use nondestruc-
not suitable for surveying with impedance scanners; however,
tive electrical impedance (EI) scanners to locate moisture and
liquid-applied aluminum pigmented emulsified asphalt-based
evaluate the comparitive moisture content within insulated
coatings shall not normally affect impedance scanner readings.
low-slope roofing and waterproofing systems.
1.4.4 SeeA1.4forsomecautionarynotesonroofinganoma-
1.2 This practice is applicable to roofing and waterproofing
lies and limitations that affect the impedance test practice.
systems wherein insulation is placed above the deck and
1.5 Moisture scanners using impedance-based technology
positioned underneath and in contact with electrically noncon-
are classified as EI scanners.
ductive single-ply or built-up roofing and waterproofing mem-
branes and systems such as coal tar, asphalt, modified bitumen,
NOTE 1—The term capacitance is sometimes used when describing
impedance scanners. Capacitance scanners are purely capacitive as they
thermoplastics, spray polyurethane foam, and similar electri-
do not have a resistive component. Impedance scanners combine both
cally nonconductive membrane materials. This practice is also
capacitance and resistance for testing; thus, they are well suited to the
applicable to roofing and waterproofing systems without insu-
measurement of different types of materials and constructions found in
lation placed above moisture absorbing decks such as wood,
roofingandwaterproofingsystemsasthecombinationofbothcomponents
concrete, or gypsum, that are in contact with single-ply or
allows for a more versatile testing, calibration, and measurement arrange-
ment.
built-up roofing and waterproofing membranes as described
above.
1.6 This practice also addresses necessary verification of
impedance data involving invasive test procedures using core
1.3 This practice is applicable to roofing and waterproofing
samples.
systems incorporating electrically nonconductive rigid board
insulation made from materials such as organic fibers, perlite,
1.7 This practice addresses two generally accepted scanning
cork, fiberglass, wood-fiber, polyisocyanurate, polystyrene,
techniques for conducting moisture surveys using electrical
phenolic foam, composite boards, gypsum substrate boards,
impedance scanners:
andotherelectricallynonconductiveroofingandwaterproofing
1.7.1 Technique A—Continuous systematic scanning and
systems such as spray-applied polyurethane foam.
recording (see 8.2), and
1.7.2 Technique B—Grid format scanning and recording
1.4 This practice is not appropriate for all combinations of
(see 8.3).
materials used in roofing and waterproofing systems.
1.4.1 Metal and other electrically conductive surface cover-
1.8 This practice addresses some meteorological conditions
ings and near-surface embedded metallic components are not
and limitations for performing impedance inspections.
suitable for surveying with impedance scanners because of the
1.9 This practice addresses the effect of the roofing or
electrical conductivity of these materials.
waterproofing construction, material differences, and exterior
1.4.2 This practice is not appropriate for use with black
surface conditions on the moisture inspections.
EPDM, any membranes containing black EPDM, or black
1.10 This practice addresses operating procedures, operator
EPDM coatings because black EPDM gives false positive
qualifications, operating methods, scanning, surveying, and
readings.
recording techniques.
1.11 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The
ThispracticeisunderthejurisdictionofASTMCommitteeD08onRoofingand
Waterproofing and is the direct responsibility of Subcommittee D08.20 on Roofing
values stated in each system may not be exact equivalents;
Membrane Systems.
therefore,eachsystemshallbeusedindependentlyoftheother.
Current edition approved Feb. 1, 2021. Published February 2021. Originally
Combining values from the two systems may result in noncon-
approvedin2014.Lastpreviouseditionapprovedin2015asD7954/D7954M – 15a.
DOI: 10.1520/D7954_D7954M-15AR21. formance with the standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7954/D7954M−15a (2021)
1.12 This standard does not purport to address all of the for impedance scanning may be returned when some other
safety concerns, if any, associated with its use. It is the electrically conductive material is present in the roofing
responsibility of the user of this standard to establish appro- system.
priate safety, health, and environmental practices and deter-
3.2.5 gravimetric analysis, n—determination of moisture
mine the applicability of regulatory limitations prior to use.
content by weight of a material by comparing wet weight to
Caution should be taken when accessing, walking, or using
oven dry weight expressed as a percentage.
scanning equipment on the roofing or waterproofing surfaces,
3.2.6 moisture content, MC, n—mass of moisture per unit
or elevated locations, when using ladders, and when raising
mass of dry material.
and lowering equipment to elevated locations.
3.2.6.1 Discussion—The moisture content is usually ex-
1.13 This international standard was developed in accor-
pressed as a percentage by weight and determined gravimetri-
dance with internationally recognized principles on standard-
cally.
ization established in the Decision on Principles for the
3.2.7 roof assembly, n—assembly of interacting roof com-
Development of International Standards, Guides and Recom-
ponents including the roof deck, air or vapor retarder, insula-
mendations issued by the World Trade Organization Technical
tion and membrane, or primary roof covering designed to
Barriers to Trade (TBT) Committee.
weatherproof a structure.
2. Referenced Documents 3.2.8 roof section, n—portion of a roof that is separated
from adjacent portions by walls or expansion joints with no
2.1 ASTM Standards:
changes in the components throughout the section.
C1616 Test Method for Determining the Moisture Content
of Organic and Inorganic Insulation Materials by Weight
4. Summary of Practice
D1079 Terminology Relating to Roofing and Waterproofing
4.1 This practice covers a procedure in which a specifically
D7438 Practice for Field Calibration and Application of
developed nondestructive electronic impedance (EI) based
Hand-Held Moisture Meters
moisture scanner is used in conjunction with interpretive data
E2586 Practice for Calculating and Using Basic Statistics
and invasive verification practices to detect and evaluate the
F2659 Guide for Preliminary Evaluation of Comparative
moisture conditions within low-sloped roofing and waterproof-
Moisture Condition of Concrete, Gypsum Cement and
ing systems by nondestructively measuring the electrical alter-
Other Floor Slabs and Screeds Using a Non-Destructive
nating current (ac) impedance.
Electronic Moisture Meter
4.2 This practice is intended to be used in conjunction with
NOTE 2—See A1.3 for other referenced documents.
the impedance scanner manufacturer’s operation instructions
and guides.
3. Terminology
5. Significance and Use
3.1 For definitions of terms used in this practice, refer to
Terminology D1079.
5.1 Excess moisture trapped in roofing or waterproofing
systems can adversely affect performance and lead to prema-
3.2 Definitions of Terms Specific to This Standard:
ture failure of roofing or waterproofing systems and its
3.2.1 comparative moisture, content, n—qualitative charac-
components. It also reduces thermal resistance, resulting in
terization of moisture content in relative terms (that is, low,
reduced energy efficiency and inflated energy costs. Impedance
medium, and high levels of moisture).
scans can be effective in identifying concealed and entrapped
3.2.2 core sample, n—small specimen of insulation and
moisture within roofing or waterproofing systems.
membrane having a minimum of 2 in. [50 mm] diameter
5.2 This practice is intended to be used at various stages of
obtained by cutting through these components down to the
deck and removing them from the roofing section under test. the roofing and waterproofing system’s life such as: during or
atcompletionofinstallationofroofingorwaterproofingsystem
3.2.2.1 Discussion—Core samples are used to verify the
to determine if there was moisture intrusion into the roofing or
membrane and insulation composition and ascertain informa-
waterproofing system or underlying materials; at regular inter-
tion on their condition.
vals as part of a preventative maintenance program; and to aid
3.2.3 detect or detection, v or n—for the purpose of imped-
in condition assessment, or before replacement or repair work,
ance scanning, the condition at which there is a consistent
or combinations thereof, to assist in determining the extent of
indication that an elevated level of impedance reading is
work and replacement materials.
present within the roofing or waterproofing system.
5.3 This practice alone does not determine the cause of
3.2.4 false-positive, adj—readingthatindicatesthatelevated
moisture infiltration into roofing or waterproofing systems;
moisture is present when it is not.
however, it can be used to help tracing excess moisture to the
3.2.4.1 Discussion—For example, a false positive in roofing
point of ingress.
6. Apparatus
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.1 EI Scanner—This apparatus shall be specifically devel-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
oped to detect and evaluate nondestructively comparative
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. moisture conditions within roofing and waterproofing systems.
D7954/D7954M−15a (2021)
FIG. 1Typical Nondestructive Moisture Scanner
6.1.1 Principles of Operation—The EI of a material varies 6.2.1 Handheld scanner designed to be used for point
in proportion with the material’s moisture content. The EI of readings on a grid system, and
materials such as those listed in 1.2 and 1.3 in the roofing or
6.2.2 Mobile-wheeled scanner, which can be rolled across
waterproofing system directly under the footprint of the scan-
the roofing or waterproofing to obtain continuous readings as
ner is measured by creating an alternating electric field that
the scanner moves over the surface.
penetrates the materials under test. The small alternating
NOTE 3—See A1.1 and A1.2 for examples of typical handheld and
current (ac) flowing through this field is inversely proportional
mobile-wheeled types of impedance scanners.
with the impedance of these moisture-absorbing materials.The
instrumentdeterminesthecurrent’samplitudeandconvertsthis
7. Operator Qualifications and Referenced Materials
value to a comparative moisture value.
6.1.1.1 The depth of the signal penetration varies depending
7.1 The operator shall:
on the sensitivity and signal strength settings of the scanner as
7.1.1 Be familiar with the use of the impedance scanner;
well as the composition of materials, thickness, and moisture
7.1.2 Have knowledge of and available for reference at the
content of the roofing or waterproofing system under test.
roof site a copy of the manufacturer’s operating and calibration
6.1.2 Apparatus Requirements:
instructions for the impedance scanner used;
6.1.2.1 The moisture scanner shall be capable of sending
7.1.3 Have knowledge of how and under what circum-
signals nondestructively into the materials below the surfacing
stances the impedance scanning system can be used, as well as
and the scanner.
its limitations;
6.1.2.2 The moisture scanner shall have integrated adjust-
able calibration ability for the differing composition, thickness, 7.1.4 Have a thorough understanding of the construction
density of materials, and moisture conditions that can be
and components used in the roofing or waterproofing system
encountered in roofing or waterproofing assemblies.
assembly under test, such as types of membranes, roofing
6.1.2.3 The moisture scanner shall have a display giving
insulations, decking, and attachment;
comparativereadingsofmoistureconditionsofmaterialsfound
7.1.5 Confirm the composition of the roofing or waterproof-
in roofing and waterproofing systems.
ing assembly and endeavor to obtain historical data regarding
the construction, age, and performance of the roofing or
6.2 Scanner Types—Two types of impedance scanners are
commercially available: waterproofing assembly; and
D7954/D7954M−15a (2021)
7.1.6 Have a thorough understanding and knowledge of rial. Ensure that materials used for marking are compatible
roofing and waterproofing technology including types of roof- with the roofing or waterproofing systems so damage does not
ing or waterproofing membranes and materials, decks, insula- occur.
tion materials, system assemblies and construction procedures,
9. Preparation
equilibrium moisture content, moisture migration in buildings,
as well as health and safety requirements when carrying out
9.1 Preparation as Applying to Both Technique A and
roofing or waterproofing moisture surveying.
B—Before commencement of nondestructive impedance
testing, the operator shall:
7.2 Data Interpreter—Individuals interpreting the field data
9.1.1 Confirm the composition of the roofing or waterproof-
shall have knowledge of: impedance scanner principles of
ing assembly and obtain any available historical data regarding
operation, moisture migration transport mechanisms, environ-
the construction, age, and performance of the roofing or
mental effects, oven dry and equilibrium moisture contents
waterproofing assembly;
(EMC), thermal resistance ratios (TRR), verification methods,
9.1.2 Obtain a roofing and waterproofing plan drawing, if
and roofing and waterproofing construction as it applies to
available; and
moisture analysis and gravimetric analysis to diagnose and
9.1.3 Prepare drawings (if not available) and survey report
interpret the readings from the roofing or
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7954/D7954M − 15a D7954/D7954M − 15a (Reapproved 2021)
Standard Practice for
Moisture Surveying of Roofing and Waterproofing Systems
Using Non-DestructiveNondestructive Electrical Impedance
Scanners
This standard is issued under the fixed designation D7954/D7954M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice applies to techniques that use non-destructivenondestructive electrical impedance (EI) scanners to locate
moisture and evaluate the comparitive moisture content within insulated low-slope roofing and waterproofing systems.
1.2 This practice is applicable to roofing and waterproofing systems wherein insulation is placed above the deck and positioned
underneath and in contact with electrically nonconductive single-ply or built-up roofing and waterproofing membranes and systems
such as coal tar, asphalt, modified bitumen, thermoplastics, spray polyurethane foam, and similar electrically non-
conductivenonconductive membrane materials. This practice is also applicable to roofing and waterproofing systems without
insulation placed above moisture absorbing decks such as wood, concrete, or gypsum, that are in contact with single-ply or built-up
roofing and waterproofing membranes as described above.
1.3 This practice is applicable to roofing and waterproofing systems incorporating electrically nonconductive rigid board
insulation 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 waterproofing systems such
as spray-applied polyurethane foam.
1.4 This practice is not appropriate for all combinations of materials used in roofing and waterproofing systems.
1.4.1 Metal and other electrically conductive surface coverings and near-surface embedded metallic components are not suitable
for surveying with impedance scanners because of the electrical conductivity of these materials.
1.4.2 This practice is not appropriate for use with black EPDM, any membranes containing black EPDM, or black EPDM coatings
because black EPDM gives false positive readings.
1.4.3 Aluminum foil on top-faced insulation, roofing, or waterproofing membranes gives a false positive reading and is not
suitable for surveying with impedance scanners; however, liquid-applied aluminum pigmented emulsified asphalt-based coatings
shall not normally affect impedance scanner readings.
1.4.4 See A1.4 for some cautionary notes on roofing anomalies and limitations that affect the impedance test practice.
1.5 Moisture scanners using impedance based impedance-based technology are classified as EI scanners.
This practice is under the jurisdiction of ASTM Committee D08 on Roofing and Waterproofing and is the direct responsibility of Subcommittee D08.20 on Roofing
Membrane Systems.
Current edition approved June 1, 2015Feb. 1, 2021. Published June 2015February 2021. Originally approved in 2014. Last previous edition approved in 2015 as
D7954/D7954M – 15.D7954/D7954M – 15a. DOI: 10.1520/D7954_D7954M-15A.10.1520/D7954_D7954M-15AR21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7954/D7954M − 15a (2021)
NOTE 1—The term capacitance is sometimes used when describing impedance scanners. Capacitance scanners are purely capacitive as they do not have
a resistive component. Impedance scanners combine both capacitance and resistance for testing; thus, they are well suited to the measurement of different
types of materials and constructions found in roofing and waterproofing systems as the combination of both components allows for a more versatile
testing, calibration, and measurement arrangement.
1.6 This practice also addresses necessary verification of impedance data involving invasive test procedures using core samples.
1.7 This practice addresses two generally accepted scanning techniques for conducting moisture surveys using electrical
impedance scanners:
1.7.1 Technique A—Continuous systematic scanning and recording (see 8.2), and
1.7.2 Technique B—Grid format scanning and recording (see 8.3).
1.8 This practice addresses some meteorological conditions and limitations for performing impedance inspections.
1.9 This practice addresses the effect of the roofing or waterproofing construction, material differences, and exterior surface
conditions on the moisture inspections.
1.10 This practice addresses operating procedures, operator qualifications, operating methods, scanning, surveying, and recording
techniques.
1.11 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values 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-conformancenonconformance with the standard.
1.12 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Caution should be taken when accessing, walking, or using scanning equipment
on the roofing or waterproofing surfaces, or elevated locations, when using ladders, and when raising and lowering equipment to
elevated locations.
1.13 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C1616 Test Method for Determining the Moisture Content of Organic and Inorganic Insulation Materials by Weight
D1079 Terminology Relating to Roofing and Waterproofing
D7438 Practice for Field Calibration and Application of Hand-Held Moisture Meters
E2586 Practice for Calculating and Using Basic Statistics
F2659 Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement and Other Floor
Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter
NOTE 2—See A1.3 for other referenced documents.
3. Terminology
3.1 For definitions of terms used in this practice, refer to Terminology D1079.
3.2 Definitions of Terms Specific to This Standard:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D7954/D7954M − 15a (2021)
3.2.1 comparative moisture, content, n—qualitative characterization of moisture content in relative terms (that is, low, medium,
and high levels of moisture).
3.2.2 core sample, n—small specimen of insulation and membrane having a minimum of 2-in. [50-mm]2 in. [50 mm] diameter
obtained by cutting through these components down to the deck and removing them from the roofing section under test.
3.2.2.1 Discussion—
Core samples are used to verify the membrane and insulation composition and ascertain information on their condition.
3.2.3 detect or detection, v or n—for the purpose of impedance scanning, the condition at which there is a consistent indication
that an elevated level of impedance reading is present within the roofing or waterproofing system.
3.2.4 false-positive, adj—reading that indicates that elevated moisture is present when it is not.
3.2.4.1 Discussion—
For example, a false positive in roofing for impedance scanning may be returned when some other electrically conductive material
is present in the roofing system.
3.2.5 gravimetric analysis, n—determination of moisture content by weight of a material by comparing wet weight to overoven
dry weight expressed as a percentage.
3.2.6 moisture content, MC, n—mass of moisture per unit mass of dry material.
3.2.6.1 Discussion—
The moisture content is usually expressed as a percentage by weight and determined gravimetrically.
3.2.7 roof assembly, n—assembly of interacting roof components including the roof deck, air or vapor retarder, insulation and
membrane, or primary roof covering designed to weatherproof a structure.
3.2.8 roof section, n—portion of a roof that is separated from adjacent portions by walls or expansion joints with no changes in
the components throughout the section.
4. Summary of Practice
4.1 This practice covers a procedure in which a specifically developed non-destructivenondestructive electronic impedance (EI)
based moisture scanner is used in conjunction with interpretive data and invasive verification practices to detect and evaluate the
moisture conditions within low-sloped roofing and waterproofing systems by non-destructivelynondestructively measuring the
electrical alternating current (ac) impedance.
4.2 This practice is intended to be used in conjunction with the impedance scanner manufacturer’s operation instructions and
guides.
5. Significance and Use
5.1 Excess moisture trapped in roofing or waterproofing systems can adversely affect performance and lead to premature failure
of roofing or waterproofing systems and its components. It also reduces thermal resistance, resulting in reduced energy efficiency
and inflated energy costs. Impedance scans can be effective in identifying concealed and entrapped moisture within roofing or
waterproofing systems.
5.2 This practice is intended to be used at various stages of the roofing and waterproofing system’s life such as: during or at
completion of installation of roofing or waterproofing system to determine if there was moisture intrusion into the roofing or
waterproofing system or underlying materials,materials; at regular intervals as part of a preventative maintenance program,
program; and to aid in condition assessment, or before replacement or repair work, or combinations thereof, to assist in determining
the extent of work and replacement materials.
5.3 This practice alone does not determine the cause of moisture infiltration into roofing or waterproofing systems; however, it can
be used to help tracing excess moisture to the point of ingress.
D7954/D7954M − 15a (2021)
6. Apparatus
6.1 EI Scanner—This apparatus shall be specifically developed to detect and evaluate non-destructivelynondestructively
comparative moisture conditions within roofing and waterproofing systems.
6.1.1 Principles of Operation—The EI of a material varies in proportion with the material’s moisture content. The EI of materials
such as those listed in 1.2 and 1.3 in the roofing or waterproofing system directly under the footprint of the scanner is measured
by creating an alternating electric field that penetrates the materials under test. The small alternating current (ac) flowing through
this field is inversely proportional with the impedance of these moisture-absorbing materials. The instrument determines the
current’s amplitude and converts this value to a comparative moisture value.
6.1.1.1 The depth of the signal penetration varies depending on the sensitivity and signal strength settings of the scanner as well
as the composition of materials, thickness, and moisture content of the roofing or waterproofing system under test.
6.1.2 Apparatus Requirements:
6.1.2.1 The moisture scanner shall be capable of sending signals non-destructivelynondestructively into the materials below the
surfacing and the scanner.
6.1.2.2 The moisture scanner shall have integrated adjustable calibration ability for the differing composition, thickness, density
of materials, and moisture conditions that can be encountered in roofing or waterproofing assemblies.
6.1.2.3 The moisture scanner shall have a display giving comparative readings of moisture conditions of materials found in roofing
and waterproofing systems.
6.2 Scanner Types—Two types of impedance scanners are commercially available:
FIG. 1 Typical Non-DestructiveNondestructive Moisture Scanner
D7954/D7954M − 15a (2021)
6.2.1 Handheld scanner designed to be used for point readings on a grid system, and
6.2.2 Mobile-wheeled scanner, which can be rolled across the roofing or waterproofing to obtain continuous readings as the
scanner moves over the surface.
NOTE 3—See A1.1 and A1.2 for examples of typical handheld and mobile-wheeled types of impedance scanners.
7. Operator Qualifications and Referenced Materials
7.1 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 the roof site a copy of the manufacturer’s operating and calibration
instructions for the impedance scanner used;
7.1.3 Have knowledge of how and under what circumstances the impedance scanning system can be used, as well as its
limitations;
7.1.4 Have a thorough understanding of the construction and components used in the roofing or waterproofing system assembly
under test, such as types of membranes, roofing insulations, decking, and attachment;
7.1.5 Confirm the composition of the roofing or waterproofing assembly and endeavor to obtain historical data regarding the
construction, age, and performance of the roofing or waterproofing assembly; and
7.1.6 Have a thorough understanding and knowledge of roofing and waterproofing technology including types of roofing or
waterproofing membranes and materials, decks, insulation materials, system assemblies and construction procedures, equilibrium
moisture content, moisture migration in buildings, as well as health and safety requirements when carrying out roofing or
waterproofing moisture surveying.
7.2 Data Interpreter—Individuals interpreting the field data shall have knowledge of: impedance scanner principles of operation,
moisture migration transport mechanisms, environmental effects, oven dry and equilibrium moisture contents (EMC), thermal
resistance ratios (TRR), verification methods, and roofing and waterproofing construction as it applies to moisture analysis and
gravim
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