National foreword

This Published Document is the UK implementation of ISO/TS 18734:2026.

The UK participation in its preparation was entrusted to Technical Committee B/517/8, Protection and repair of concrete structures.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

This publication is not to be regarded as a British Standard.

Compliance with a Published Document cannot confer immunity from legal obligations.

This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 January 2026.

Foreword

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This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre stressed concrete, Subcommittee SC 7, Maintenance and concrete structures.

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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 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.

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.

Ambient and environmental conditions of underground concrete structures
Types of barriers used for waterproofing and protection
Performance requirement for waterproofing and protection
Performance evaluation for waterproofing and protection
Selection procedure of optimal waterproofing and protection

2 Normative references

3 Terms and definitions

4 Importance and requirements for underground concrete structure waterproofing

4.1 Importance

4.2 Requirements

5 Factors to consider for underground concrete structure waterproofing and protection

5.1 Underground Environment Analysis of Construction Area

5.2 Chemical Environment Effects

5.3 Physical environment effects

6 Types of membranes for waterproofing and protection

6.1 General

6.2 Types of materials used for waterproofing and protection

7 Performance requirements and test for waterproofing and protection

7.1 General

7.2 General physical properties

7.3 Hydrostatic pressure resistance

7.4 Crack movement resistance

7.5 Chemical resistance

7.6 Bonding resistance

7.7 Lateral water migration resistance

7.8 Durability

8 Selection procedure of optimal waterproofing and protection

8.1 General

8.2 Installation method considering below ground construction method

8.3 Service and environmental conditions

8.4 Structure importance and service life

8.5 Selection procedure

Bibliography

PD ISO/TS 18734:2026

Requirements and recommendations for elastic barriers, waterproofing and protection of underground concrete structures

Current

Published:

31 Jan 2026