ISO/TS 18734
(Main)Guidelines and requirements for elastic barriers, waterproofing and protection of underground concrete structures
Guidelines and requirements for elastic barriers, waterproofing and protection of underground concrete structures
Water-leakage of underground concrete structures shall be performed on the damage of not only materials, members and structural levels but also property value and life safety. This document shall apply to the underground concrete structural members (mainly wall and bottom slab) of civil engineering structures including buildings, subway or tunnels constructed as plain or reinforced concrete structure (including steel framed reinforced concrete construction) deteriorated or damaged due to water, contaminants, gases and movement.
Lignes directrices et exigences pour les membranes élastiques, l'étanchéité et la protection des structures en béton souterraines
General Information
Standards Content (Sample)
FINAL DRAFT
Technical
Specification
ISO/DTS 18734
ISO/TC 71/SC 7
Guidelines and requirements for
Secretariat: KATS
elastic barriers, waterproofing and
Voting begins on:
protection of underground concrete
2025-10-07
structures
Voting terminates on:
2025-12-02
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/DTS 18734:2025(en) © ISO 2025
FINAL DRAFT
ISO/DTS 18734:2025(en)
Technical
Specification
ISO/DTS 18734
ISO/TC 71/SC 7
Guidelines and requirements for
Secretariat: KATS
elastic barriers, waterproofing and
Voting begins on:
protection of underground concrete
structures
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ISO/DTS 18734:2025(en) © ISO 2025
ii
ISO/DTS 18734:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Importance and requirements for underground concrete structure waterproofing . 2
4.1 Importance . .2
4.2 Requirements .2
5 Factors to consider for underground concrete structure waterproofing and protection . 3
5.1 Underground Environment Analysis of Construction Area .3
5.1.1 General .3
5.1.2 Site/Location Environment .3
5.2 Chemical Environment Effects .4
5.2.1 Chlorine .4
5.2.2 Acid, Alkali, Lactate damage .4
5.2.3 Oil and organic compounds .4
5.2.4 Ground Gas .4
5.3 Physical environment effects .5
5.3.1 Ground water .5
5.3.2 Interaction with soil .5
5.3.3 Structural displacement and deformation .5
6 Types of membranes for waterproofing and protection . 5
6.1 General .5
6.2 Types of materials used for waterproofing and protection .6
6.2.1 Liquid applied type .6
6.2.2 Sheet applied type .7
6.2.3 Multi (composite) layers type .8
7 Performance requirements and test for waterproofing and protection . 8
7.1 General .8
7.2 General physical properties .8
7.3 Hydrostatic pressure resistance .9
7.4 Crack movement resistance .9
7.5 Chemical resistance .9
7.6 Bonding resistance .9
7.7 Lateral water migration resistance .9
7.8 Durability .9
8 Selection procedure of optimal waterproofing and protection .10
8.1 General .10
8.2 Installation method considering below ground construction method .10
8.2.1 Cut and cover .10
8.2.2 Soil retention wall .10
8.3 Service and environmental conditions .10
8.4 Structure importance and service life .10
8.5 Selection procedure .11
8.5.1 Step 1 : Construction method ( Pre applied / Post applied method ).11
8.5.2 Step 2 : Environment conditions .11
8.5.3 Step 3 : Importance and use of underground structures .11
Bibliography .13
iii
ISO/DTS 18734:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre
stressed concrete, Subcommittee SC 7, Maintenance and concrete structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO/DTS 18734:2025(en)
Introduction
This document presents the principles applicable to barriers used for waterproofing and protection on the
positive side (exterior side of concrete wall/floor) as a method of preventing hydrostatic penetration into
the negative space of underground concrete structures and protecting concrete structures against chemical
contaminants and gases to provide safety, and comfortable environment for users. Positive-side barriers can
generally be categorized into two categories: 1) post applied method (installation after concrete casting and
curing) and 2) pre applied method (installation before concrete casting and curing). In the past, post applied
methods were common: the barrier was installed on existing, cured concrete walls, in a similar way as what
was done in roofing. Pre applied methods were developed more recently. With the pre applied methods, the
barrier is applied on the formwork, shutter or lost formwork. Concrete is then cast directly on the barrier.
In buildings built with foundations extending below the groundwater surface, the surface of the wall in
contact with the soil must be protected from the groundwater. The groundwater, or some chemical from the
soil may enter the concrete of the underground structure, impairing its integrity, deteriorating the indoor
environment which may incur important remediation cost. In some cases, the groundwater is collected
and discharges into the sewage. However, continuous groundwater discharge may create social problems
caused by groundwater depletion and ground subsidence. In addition, modern structures frequently use
underground volume in a similar fashion as above ground volumes, including for human residence or
business activity, which requires an extremely high quality of environment. Underground waterproofing is
an effective countermeasure against such a situation.
In addition, if water from the ground is in direct contact with the reinforced concrete structure of the
basement, there is a possibility that moisture can reach and eventually corrode the reinforcing bars. In
beach areas, groundwater may contain chloride ions, which can further accelerate corrosion of reinforcing
bars. Therefore, waterproofing and protecting the reinforced concrete structure in the basement is also
useful to preserve the durability of the building.
Among the performances required for the basement exterior wall, the most important thing along with
the structural performance as a building is to prevent water from entering the basement exterior wall.
Therefore, the required performance of the outer basement waterproofing and protection layer used is the
first required performance to prevent water from entering the basement like the rooftop and outer wall
waterproofing.
Since it is an environment in contact with the surrounding ground containing groundwater for a long
period of time, it should be a material that is safe for concrete or groundwater in the surrounding area.
Specifically, it should not be eroded by may be exposed to chemicals or gases such as alkali, ground, salt and
acid components contained in the groundwater, and gases of concrete, that is, it should not or contaminate
the surrounding ground or groundwater with the elution component of the waterproofing and protection
materials. In addition, for long-term protection of underground concrete structures, the ability of the
membrane to waterproof the structure, to protect the structure, resist structural stresses, aging, and offer
adequate chemical and gas resistance are also required. Therefore, for external barriers of an underground
structure, a waterproof design should be performed in consideration of the construction method of the
underground concrete structure, the environmental conditions of the basement, the factors of concrete
performance degradation, and the performance required for the waterproofing and protection material.
v
FINAL DRAFT Technical Specification ISO/DTS 18734:2025(en)
Guidelines and requirements for elastic barriers,
waterproofing and protection of underground concrete
structures
1 Scope
This document intends to provide a guideline for barriers waterproofing and protection specific to the
protection against leakage and contamination underground conditions for underground concrete structures.
This document addresses the following topics in the coming sections.
a) Ambient and environmental conditions of underground concrete structures
b) Types of barriers used for waterproofing and protection
c) Performance requirement for waterproofing and protection
d) Performance evaluation for waterproofing and protection
e) Selection procedure of optimal waterproofing and protection
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
groundwater
water in the ground outside the structure from any sources
3.2
hydrostatic pressure
pressure exerted by depth of water
3.3
waterproof
impervious to free water
Note 1 to entry: This can also be known as watertight.
3.4
waterproofing
application of waterproof/water-resisting materials
ISO/DTS 18734:2025(en)
3.5
waterproofing system
materials and methods used to protect a structure from water ingress, and which might also provide
resistance to the diffusion of water vapour
3.6
leakage
flow rate of liquid (water) flowing through the concrete structure through a crack, hole, joint or weak
concrete spots (honeycomb)
3.7
pre applied method
method to install waterproofing on ground soils, basement lean concrete, soil retention walls, and
conventional structures before concrete casting and structure building
3.8
post applied method
method to install waterproofing on cured concrete and completed hardened structures
4 Importance and requirements for underground concrete structure waterproofing
4.1 Importance
Water ingress in a building enclosure can take place by below two mechanisms:
1) Liquid migration by permeation or capillary action.
2) Flow through cracks or holes in the structure by hydrostatic pressure.
Moreover, concrete is a highly durable material, but only under the condition that it is protected from water
and pollutants (chemicals, etc.). Aging (deterioration) occurs when concrete comes into continuous and
direct contact with these elements. Therefore, a high level of attention and care shall be given in vulnerable
sections such as the joint sections of concrete and appropriate waterproofing measures should be planned
for these defects at the design stage.
Leakage through construction/expansion joints, thru-wall penetrations, cracks, etc. from the soil (positive
side of concrete walls and floors) to the building enclosure (negative side) can lead to deterioration of the
indoor environment. This can reduce comfort in the underground indoor space, compromises the service
of appliances, create environmental risk, which also result in the reduction of property value and hygienic
problems such as mold and micro bacterial growth. Permanent, or occasional occupants of underground
concrete structures subject to continuous leakage can be exposed to health risks caused by air pollution,
mold and microbial inhalation, and exposition to groundwater containing harmful components. Water
leakage also triggers corrosion of reinforcing bars inside concrete structures, leading to spalling or
delamination of concrete, reduction of concrete strength, therefore reducing long-term durability and safety
of the entire structure.
A material shall therefore be installed on the concrete to prevent water ingress by permeation, capillary
action or vapor migration, as well as to bridge gaps and holes through which water could flow into the
building enclosure.
4.2 Requirements
The waterproofing material and protection shall be able to prevent exposition of the concrete to water,
ground gases, chemical contaminants to avoid premature degradation and to stop the ingress of water
through cracks and other defects for underground concrete structures. It shall therefore be a very low
permeability material, capable to elongate over a crack without tearing and to resist puncture by the
adjacent material.
Concrete has high watertightness itself, but water permeability coefficient varies greatly depending on the
conditions of the water cement ratio. The larger the water permeability coefficient, the easier water can
ISO/DTS 18734:2025(en)
permeate (the higher the water permeability). In addition, joints and crack formation are inevitable during
construction, and at the construction site, joints, expansion joints, tie holes, cracks, other defects occurring
during the concrete construction process can just as easily occur. Due to these naturally occurring elements,
it is difficult to maintain complete watertightness with concrete alone.
Even if the water table is not expected to reach the concrete surface, waterproofing and protection is still
required for below ground concrete structures because protection is still required to prevent concrete
deterioration from ground gases, chemical contaminants such as hydrocarbons, salts, and other chemical
contaminants.
5 Factors to consider for underground concrete structure waterproofing and
protection
5.1 Underground Environment Analysis of Construction Area
5.1.1 General
Positive side of underground structures is affected by the chemicals produced by the interaction of
groundwater and soil mineral components, and the physical environment such as flow rate, settlement, and
vibration. Chemical environmental impact refers to the effect of chlorine ions, acid and alkali components,
sulphate ions, oil components, radon and methane gas in groundwater and soil on the durability and safety of
structures and waterproofing layers. Physical environmental impact refers to the effect of vibration caused
by contraction and expansion according to temperature change in the basement, groundwater pressure and
earth pressure action, differential subsidence, earthquake or vehicle load, etc. on the durability and safety
of the waterproof layer such as joints, cracks, joints, etc. Since these chemical and physical effects reduce
the performance of the materials used, concrete and waterproofing materials shall have a response force
in an eroded environment and shall have stability to resist long-term erosion. Therefore, in order to secure
durability stability and prevent leakage of underground structures, it is necessary to review the selection of
appropriate waterproofing materials and construction methods in the design stage in consideration of the
underground environment of the area to be constructed, and various necessary matters in the construction
process.
5.1.2 Site/Location Environment
In order to secure the safety of the waterproofing and protection layer installed on the outer surface of the
structure, the conditions of groundwater and soil in the area where the common structure is to be built
are reviewed in advance. This is because, depending on the construction area, the conditions of chemical
components contained in groundwater and soil, hydraulic conditions, and earth pressure conditions have a
large effect on concrete and waterproofing layers. Groundwater and soil conditions to be reviewed according
to the conditions of the planned construction area are shown in Table 1.
ISO/DTS 18734:2025(en)
Table 1 — Underground water types and conditions outlined
Area Type Underground Water Condition, Status, Environment
In general, there are few harmful chemical components in the water of river areas formed inland, but
Riverside Areas
salt water can potentially be contained in rivers that are connected to the sea.
− −
Seawater Cl ions and SO4 ions are included in the coastal area, causing erosion of concrete, steel
Seaside Areas
and some waterproofing materials.
The hot spring water depends on the hydrogen ion concentration (pH): strong acidic spring (pH 2 or
less), acidic spring (pH 2-4 or less), weakly acidic spring (pH 4-6 or less), neutral spring (pH 6-7,5 or
Hot springs
less), weak alkaline spring (pH 7,5 to less than 8,5), alkaline spring ((pH less than 8,5 to 10), strong
Areas
− − −
alkaline spring (more than pH 10), HCO3 ions, Cl ions, SO4 ions, etc. exist in the hot spring water. It
causes erosion of concrete, steel, and some types of waterproofing materials.
In general, there are few chemical components in the groundwater and soil that adversely affect the
Mountain Areas waterproofing layer in the mountain areas, but water pressure of the groundwater descending from
the mountain is generally much higher than other areas.
Petrochemical plants, gas stations, and large oil tanks (military facilities) can flow out from places
Oil Storage
where gasoline, kerosene, diesel, etc. are installed, polluting groundwater and soil and damaging the
Areas
waterproofing layer.
Chemical water generated from mine development areas, landfill areas, waste concrete crushing plants,
Leaching Water
ready-mixed concrete plants, etc. can flow into the basement, contaminating groundwater and soil,
Drainage Area
and damaging the waterproofing layer.
5.2 Chemical Environment Effects
5.2.1 Chlorine
The penetration of chlorine ions presents in the groundwater and soil of the seashore has high influence
on the increase of corrosion risk in concrete reinforcing rebars. The aging of concrete structures due to
salt damage appears in a wide variety of forms, including corrosio
...
ISO CD TS/DTS 18734:####(X)
ISO/TC 71/SC 7
Secretariat : : KATS
Date: 2025-09-22
Guidelines and Requirements for Elastic Barriers, Waterproofing and
Protection of Underground Concrete Structures
CD stage
Warning for WDs and CDs
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change
without notice and may not be referred to as an International Standard.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which
they are aware and to provide supporting documentation.
A model document of an International Standard (the Model International Standard) is available at:
© ISO #### – All rights reserved
ISO/DTS 18734:(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: copyright@iso.org
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii
ISO CD TS/DTS 18734:####(X:(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Importance and requirements for underground concrete structure waterproofing . 2
4.1 Importance . 2
4.2 Requirements . 3
5 Factors to consider for underground concrete structure waterproofing and protection . 3
5.1 Underground Environment Analysis of Construction Area . 3
5.2 Chemical Environment Effects . 4
5.3 Physical environment effects . 5
6 Types of membranes for waterproofing and protection . 6
6.1 General . 6
6.2 Types of materials used for waterproofing and protection . 7
7 Performance requirements and test for waterproofing and protection . 9
7.1 General . 9
7.2 General physical properties . 10
7.3 Hydrostatic pressure resistance . 10
7.4 Crack movement resistance . 10
7.5 Chemical resistance . 10
7.6 Bonding resistance . 10
7.7 Lateral water migration resistance . 11
7.8 Durability . 11
8 Selection procedure of optimal waterproofing and protection . 11
8.1 General . 11
8.2 Installation method considering below ground construction method . 11
8.3 Service and environmental conditions . 12
8.4 Structure importance and service life . 12
8.5 Selection procedure . 12
Bibliography . 14
© ISO #### 2025 – All rights reserved
iii
ISO/DTS 18734:(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Field Code Changed
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
Field Code Changed
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre
stressed concrete, Subcommittee SC 7, Maintenance and concrete structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO CD TS/DTS 18734:####(X:(en)
Introduction
This document presents the principles applicable to barriers used for waterproofing and protection on the
positive side (exterior side of concrete wall/floor) as a method of preventing hydrostatic penetration into the
negative space of underground concrete structures and protecting concrete structures against chemical
contaminants and gases to provide safety, and comfortable environment for users. Positive-side barriers can
generally be categorized into two categories: 1) post applied method (installation after concrete casting and
curing) and 2) pre applied method (installation before concrete casting and curing). In the past, post applied
methods were common: the barrier was installed on existing, cured concrete walls, in a similar way as what
was done in roofing. Pre applied methods were developed more recently. With the pre applied methods, the
barrier is applied on the formwork, shutter or lost formwork. Concrete is then cast directly on the barrier.
In buildings built with foundations extending below the groundwater surface, the surface of the wall in contact
with the soil must be protected from the groundwater. The groundwater, or some chemical from the soil may
enter the concrete of the underground structure, impairing its integrity, deteriorating the indoor environment
which may incur important remediation cost. In some cases, the groundwater is collected and discharges into
the sewage. However, continuous groundwater discharge may create social problems caused by groundwater
depletion and ground subsidence. In addition, modern structures frequently use underground volume in a
similar fashion as above ground volumes, including for human residence or business activity, which requires
an extremely high quality of environment. Underground waterproofing is an effective countermeasure against
such a situation.
In addition, if water from the ground is in direct contact with the reinforced concrete structure of the
basement, there is a possibility that moisture can reach and eventually corrode the reinforcing bars. In beach
areas, groundwater may contain chloride ions, which can further accelerate corrosion of reinforcing bars.
Therefore, waterproofing and protecting the reinforced concrete structure in the basement is also useful to
preserve the durability of the building.
Among the performances required for the basement exterior wall, the most important thing along with the
structural performance as a building is to prevent water from entering the basement exterior wall. Therefore,
the required performance of the outer basement waterproofing and protection layer used is the first required
performance to prevent water from entering the basement like the rooftop and outer wall waterproofing.
Since it is an environment in contact with the surrounding ground containing groundwater for a long period
of time, it should be a material that is safe for concrete or groundwater in the surrounding area. Specifically,
it should not be eroded by may be exposed to chemicals or gases such as alkali, ground, salt and acid
components contained in the groundwater, and gases of concrete, that is, it should not or contaminate the
surrounding ground or groundwater with the elution component of the waterproofing and protection
materials. In addition, for long-term protection of underground concrete structures, the ability of the
membrane to waterproof the structure, to protect the structure, resist structural stresses, aging, and offer
adequate chemical and gas resistance are also required. Therefore, for external barriers of an underground
structure, a waterproof design should be performed in consideration of the construction method of the
underground concrete structure, the environmental conditions of the basement, the factors of concrete
performance degradation, and the performance required for the waterproofing and protection material.
© ISO #### 2025 – All rights reserved
v
ISO CD TS/DTS 18734:####(X:(en)
Guidelines and Requirements for Elastic Barriers, Waterproofing and
Protection of Underground Concrete Structures
1 Scope
This document intends to provide a guideline for barriers waterproofing and protection specific to the
protection against leakage and contamination underground conditions for underground concrete structures.
This document addresses the following topics in the coming sections.
a) a) Ambient and environmental conditions of underground concrete structures
b) b) Types of barriers used for waterproofing and protection
c) c) Performance requirement for waterproofing and protection
d) d) Performance evaluation for waterproofing and protection
e) e) Selection procedure of optimal waterproofing and protection
2 Normative references
The following referenced document is indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN13967+A1 : 2017 : 2012, Flexible waterproofing. Plastic and rubber damp proof sheets including plastic
and rubber basement tanking sheet – Definitions and characteristics.
EN13969 : 2004, Flexible sheets for waterproofing. Bitumen damp proof sheet including bitumen basement
tanking sheets – Definitions and characteristics.
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
groundwater
water in the ground outside the structure from any sources
3.2
hydrostatic pressure
pressure exerted by depth of water
3.3
waterproof
impervious to free water / NOTE
© ISO #### 2025 – All rights reserved
ISO/DTS 18734:(en)
Note 1 to entry: This can also be known as watertight.
3.4
waterproofing
application of waterproof/water-resisting materials
3.5
waterproofing system
materials and methods used to protect a structure from water ingress, and which might also provide
resistance to the diffusion of water vapour
3.6
leakage
flow rate of liquid (water) flowing through the concrete structure through a crack, hole, joint or weak concrete
spots (honeycomb)
3.7 thermal stability
physical stability of barriers in response to temperature fluctuations in the atmosphere or underwater
3.8 water resistance
3.93.7 ability to withstand a water pressure without leaking
pre applied method
ismethod to install waterproofing on ground soils, basement lean concrete, soil retention walls, and
conventional structures before concrete casting and structure building
3.103.8
post applied method
ismethod to install waterproofing on cured concrete and completed hardened structures
4 Importance and Requirementsrequirements for Underground Concrete Structure
Waterproofing underground concrete structure waterproofing
4.1 Importance
Water ingress in a building enclosure can take place by below two mechanisms:
1) Liquid migration by permeation or capillary action.
2) Flow through cracks or holes in the structure by hydrostatic pressure.
Moreover, concrete is a highly durable material, but only under the condition that it is protected from water
and pollutants (chemicals, etc.). Aging (deterioration) occurs when concrete comes into continuous and direct
contact with these elements. Therefore, a high level of attention and care shall be given in vulnerable sections
such as the joint sections of concrete and appropriate waterproofing measures should be planned for these
defects at the design stage.
Leakage through construction/expansion joints, thru-wall penetrations, cracks, etc. from the soil (positive side
of concrete walls and floors) to the building enclosure (negative side) can lead to deterioration of the indoor
environment. This can reduce comfort in the underground indoor space, compromises the service of
appliances, create environmental risk, which also result in the reduction of property value and hygienic
problems such as mold and micro bacterial growth. Permanent, or occasional occupants of underground
concrete structures subject to continuous leakage can be exposed to health risks caused by air pollution, mold
and microbial inhalation, and exposition to groundwater containing harmful components. Water leakage also
triggers corrosion of reinforcing bars inside concrete structures, leading to spalling or delamination of
ISO CD TS/DTS 18734:####(X:(en)
concrete, reduction of concrete strength, therefore reducing long-term durability and safety of the entire
structure.
A material shall therefore be installed on the concrete to prevent water ingress by permeation, capillary action
or vapor migration, as well as to bridge gaps and holes through which water could flow into the building
enclosure.
4.2 Requirements
The waterproofing material and protection shall be able to prevent exposition of the concrete to water, ground
gases, chemical contaminants to avoid premature degradation and to stop the ingress of water through cracks
and other defects for underground concrete structures. It shall therefore be a very low permeability material,
capable to elongate over a crack without tearing and to resist puncture by the adjacent material.
Concrete has high watertightness itself, but water permeability coefficient varies greatly depending on the
conditions of the water cement ratio. The larger the water permeability coefficient, the easier water can
permeate (the higher the water permeability). In addition, joints and crack formation are inevitable during
construction, and at the construction site, joints, expansion joints, tie holes, cracks, other defects occurring
during the concrete construction process can just as easily occur. Due to these naturally occurring elements,
it is difficult to maintain complete watertightness with concrete alone.
Even if the water table is not expected to reach the concrete surface, waterproofing and protection is still
required for below ground concrete structures because protection is still required to prevent concrete
deterioration from ground gases, chemical contaminants such as hydrocarbons, salts, and other chemical
contaminants.
5 Factors to consider for underground concrete structure waterproofing and
protection
5.1 Underground Environment Analysis of Construction Area
5.1.1 General
Positive side of underground structures is affected by the chemicals produced by the interaction of
groundwater and soil mineral components, and the physical environment such as flow rate, settlement, and
vibration. Chemical environmental impact refers to the effect of chlorine ions, acid and alkali components,
sulphate ions, oil components, radon and methane gas in groundwater and soil on the durability and safety of
structures and waterproofing layers. Physical environmental impact refers to the effect of vibration caused by
contraction and expansion according to temperature change in the basement, groundwater pressure and earth
pressure action, differential subsidence, earthquake or vehicle load, etc. on the durability and safety of the
waterproof layer such as joints, cracks, joints, etc. Since these chemical and physical effects reduce the
performance of the materials used, concrete and waterproofing materials shall have a response force in an
eroded environment and shall have stability to resist long-term erosion. Therefore, in order to secure
durability stability and prevent leakage of underground structures, it is necessary to review the selection of
appropriate waterproofing materials and construction methods in the design stage in consideration of the
underground environment of the area to be constructed, and various necessary matters in the construction
process.
5.1.2 Site/Location Environment
In order to secure the safety of the waterproofing and protection layer installed on the outer surface of the
structure, the conditions of groundwater and soil in the area where the common structure is to be built are
reviewed in advance. This is because, depending on the construction area, the conditions of chemical
components contained in groundwater and soil, hydraulic conditions, and earth pressure conditions have a
© ISO #### 2025 – All rights reserved
ISO/DTS 18734:(en)
large effect on concrete and waterproofing layers. Groundwater and soil conditions to be reviewed according
to the conditions of the planned construction area are shown in Table 1[Table 1].
Table 1 — Underground water types and conditions outlined
Area Type Underground Water Condition, Status, Environment
Riverside In general, there are few harmful chemical components in the water of river areas formed inland,
Areas but salt water can potentially be contained in rivers that are connected to the sea.
− −
Seawater Cl⁻ ions and SO4⁻ ions are included in the coastal area, causing erosion of concrete, steel
Seaside Areas
and some waterproofing materials.
The hot spring water depends on the hydrogen ion concentration (pH): strong acidic spring (pH 2
or less), acidic spring (pH 2-4 or less), weakly acidic spring (pH 4-6 or less), neutral spring (pH 6-
Hot springs
7.,5 or less), weak alkaline spring (pH 7.,5 to less than 8.,5), alkaline spring ((pH less than 8.,5 to
Areas
− − −
10), strong alkaline spring (more than pH 10), HCO3⁻ ions, Cl⁻ ions, SO4⁻ ions, etc. exist in the
hot spring water. It causes erosion of concrete, steel, and some types of waterproofing materials.
In general, there are few chemical components in the groundwater and soil that adversely affect the
Mountain
waterproofing layer in the mountain areas, but water pressure of the groundwater descending from
Areas
the mountain is generally much higher than other areas.
Petrochemical plants, gas stations, and large oil tanks (military facilities) can flow out from places
Oil Storage
where gasoline, kerosene, diesel, etc. are installed, polluting groundwater and soil and damaging
Areas
the waterproofing layer.
Leaching Chemical water generated from mine development areas, landfill areas, waste concrete crushing
Water plants, ready-mixed concrete plants, etc. can flow into the basement, contaminating groundwater
Drainage Area and soil, and damaging the waterproofing layer.
5.2 Chemical Environment Effects
5.2.1 Chlorine
The penetration of chlorine ions presents in the groundwater and soil of the seashore has high influence on
the increase of corrosion risk in concrete reinforcing rebars. The aging of concrete structures due to salt
damage appears in a wide variety of forms, including corrosion of reinforcing bars, cracks of concrete, peeling,
delamination, and rupture of reinforcing bars, and may eventually lose its function as a structure and lead to
collapse. In addition, chlorine ions cause performance degradation such as deterioration of surface, loss of
watertightness, change of physical properties of concrete structures.
Figure 1 — Chloride attack on concrete structures
5.2.2 Acid, Alkali, Lactate damage
Concrete underground structures are always in contact with soil and groundwater, and underground
structures in industrial or coastal areas are exposed to chemicals (such as acids, alkalis, salt water, calcium
hydroxide or carbon dioxide). In particular, in the groundwater and soil of factory areas, hot spring areas, and
ISO CD TS/DTS 18734:####(X:(en)
contaminated areas, acids, alkalis, and sulfates cause concrete volume expansion, cracks and delamination due
to erosion, and neutralization, and surface deterioration, and watertightness of concrete structures. This can
cause performance degradation, such as loss or change in physical properties, resulting in water leakage.
Figure 2 — Acid, alkali and lactate attack on concrete structures
5.2.3 Oil and organic compounds
Benzene, toluene, ethylbenzene, and xylene, which are representative pollutants of soil and groundwater, are
very toxic. Some materials may not be an effective barrier against these or may be chemically incompatible.
When oil or organic compounds are present in the soil, the membrane shall be selected for its compatibility
with them.
5.2.4 Ground Gas
5.2.4.1 Radon gas
Radon is a radioactive, colorless, and odorless gas that occurs naturally in the presence of uranium and radium
and is considered a major cause of lung cancer in many research cases. Since radon is released into the
atmosphere between cracked rock masses, radon can accumulate in a higher concentration than in the outside
atmosphere in the interior or basement of some buildings with poor ventilation, so radon is also found in hot
spring water, mineral water, and groundwater. Radon enters indoors not only through the ground, but also
through building materials, water supply, natural gas for cooking, and groundwater. Although waterproofing
materials are sometimes also used to block the intrusion of radon gas in a building, they are never used alone
and are part of a system. When Radon is detected in the soil, additional investigations are required and usually
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