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Newton’s Solution Sheets

Newton’s library of Solution Sheets provide any waterproofing designer with a complete specification tool. Each Solution Sheet presents a complete waterproofing design and provides all of the key product information required to specify it, from NBS Clauses to 2D details, CAD drawings, and 3D drawings.

The Solution Sheets are also an integral part of the Newton Waterproofing Index (NWI), our scoring system for waterproofing designs. Every single Solution Sheet has been allocated with a score on the NWI that has also been audited by Newton’s independent insurer, and which indicates our expert opinion on the designs’ likelihood of success, dependent on the type of structure and the products being used.

Use the tiles below to select your type of structure, then view the range of waterproofing solutions that are available in order to achieve different levels of waterproofing protection.

Note: This article was written by Bob Cather (BSc, CEng, FIMMM) when the British Standard 8102:2009 version was the prevalent code of practice for the protection of below-ground structures against water from the ground.

 

The question of whether to use a ‘tanking’ membrane or a specialist waterproofing admixture to create a waterproof concrete waterproofing structure is a regular feature in the overall design of concrete structures, be it basements, tunnels, water tanks, swimming pools etc.

Waterproofing of Concrete Admixtures – How do Concrete Admixtures Work?

There are very many ‘waterproofing’ admixtures on the market worldwide that can be added to the concrete at mixing intended to achieve enhanced resistance to water migration. Across the range of products, there are many common features and differences. The promotion of these systems through the pages of this journal and elsewhere, often comes with attractive claims for performance, ease of use and backup ‘warranties’.

Although the different products may claim different composition and or mode of action – pore-lining repellency, crystal forming pore blocking, organic pore plugging under pressure – the presentation of claims, technical back-up, warranties have much in common across the majority of the products offered.

This discussion paper seeks to bring together the key issues and claims and presents some evaluation of the materials and invites a rigorous debate of benefits and expectations.

This is not intended to be a specific approval or rebuttal of individual claims on specific individual products. Although there is reference made to some UK technical documents, the materials, the claims and the issues are relevant worldwide.

Two headline views, derived below, is that the use of such admixtures alone is very unlikely to substantially improve the structural concrete’s ability to resist the passage of liquid water and any claimed improvement to the resistance to water vapour, is more uncertain. An important distinction is made, here and later in this paper, between water penetration through ‘structural concrete and that through a structure constructed in concrete.

BS 8102:2009 Section 9 – Achieving ‘Structurally Integral Protection’

This discussion paper is relevant now for the UK and other countries using British Standards for waterproofing underground structures. British Standard BS 8102 (1) has been revised and republished. Section 9 of the Standard relates to the selection of materials to achieve ‘structurally integral protection’ – that is where the concrete itself is required to give the required degree of resistance to minimise the ingress of water.

Clause 9.2.1.3 Concrete containing waterproofing admixtures, states in a commentary:

“There is a range of products, generally recognised as waterproofing admixtures, which seeks different ways to increase the inherent resistance of concrete to water and water vapour. As the mechanism used by each product to achieve these aims are quite diverse, it is not possible in this British Standard to give specific guidance on their use”

So it is up to the individual to judge.

It also advises that waterproofing admixtures are specified in BS EN 934 (2). That standard specifies testing to EN 480-1 and EN 480-5. However the requirement for ‘capillary absorption’ – the relevant property of those required in the standard in regard to waterproofing – is of the reduction in water absorption by a reference mortar. This is not very useful in assessing the likely water penetration performance of concrete.

BBA Certification For Admixtures

A source of independent assessment of products outside the national standards is certification by Agrément or other technical approval bodies. The British Board of Agrément has examined some of these waterproofing admixtures and has issued certificates of performance.

These certificates generally record that concretes containing the special admixture produce concrete with lower water permeability compared to a reference concrete. The certificates are more ambivalent about effects of adopting these modified concretes on the overall water exclusion of a below ground structure.

Water Leakage Through Cracks and Service Penetrations

It is common experience, drawn from real projects that water leakage through a concrete structure is predominantly not through the body of well compacted concrete, but rather where the concrete isn’t – at cracks, at joints at service penetrations, etc. Where the concrete itself is of poor quality – exhibiting poor compaction or having inclusions – there may be water leakage but the admixtures seeking to ‘improve’ the concrete matrix cannot be expected to provide benefit in such circumstances.

Thus although the concrete containing the admixture may be shown to have higher resistance to water ingress, this does not mean the structure itself will be more resistant. The argument that structural quality concrete has a very high degree of inherent ‘waterproofness’ is supported by many so-called ‘permeability’ tests that have been carried out (3). Establishing a true ‘flow’ condition in a laboratory test is extremely difficult for concrete representing the low permeability mass typical of structural concrete.

More success in demonstrating resistance to water passage has been achieved using pressure penetration methods. One such test method is set out in BS EN 12390-8:2000. In that test, concrete samples are subject to an applied pressure of 500kPa (approx 50m water head) for a period of 72hrs. The results obtained for structural concretes range from 10 – 40mm penetration.

Water Permeability

There is also some doubt as to whether the apparent improvement in water permeability property of the concretes tested by the certification bodies, is actually from the ‘active’ ingredient and not due to other changes between the control concrete and the test concrete. The table below summarises the data from some issued assessment certificates. It shows and contrasts the composition and performance detail declared.

A first comment to make is that, according to guidance on permeability (3), all of the permeability results above – test and control – would be classified of concrete of low permeability (concrete permeability < 10 -12) . There is a further degree of uncertainty about the conclusiveness of these tests, if the permeability results shown in the table for the notionally similar control specimens.

If we have good quality concrete, that is good enough in terms of permeability is there really benefit in making a concrete that is say, five times better?

For some of the products above e.g. ‘δ’ or ‘ε’ the differences in permeability could plausibly derive from the substantial reduction in w/c ratio between control and test. The link between w/c ratio and permeability is well established.

From the above arguments, there seems little benefit in adopting a special formulation waterproofing admixture to achieve better resistance against liquid water ingress.

These arguments typically come up in a contractor suggested alternative to a membrane-based waterproofing design. But, if the concrete itself can be waterproof enough – with judicious attention to joints and penetrations – why opt for a membrane at all? Confidence, habit, vapour control, durability? The factors and guidance involved with these wider issues are, at present rather less well defined and conclusions rather more difficult to draw.

Water Vapour Permeability Considerations

We would instinctively conclude perhaps, that whilst concrete can exclude liquid water it may permit passage of water vapour. It is true that making measurements of water vapour permeability is easier to achieve than with liquid water. The major uncertainty with consideration of water vapour is to decide what level of vapour ingress can be permitted. The terminology used in some design guides do not help – ‘dry’ or ‘totally dry’ – define the required transmission performance of the concrete. Additionally, the design for control of water vapour ingress is to a greater extent influenced by the nature of the use of the internal space and the mechanical services – dehumidification, ventilation etc. This has been recognised by the revision to BS 8102 has removed the previous Grade 4 environment.

The Agrément certificates for some of the waterproofing admixtures have attempted to put a performance requirement on the concrete that would meet vapour resistance needs of the superseded BS 8102. However, on the values stated and allowing for typical concrete construction sections, it can be shown that the control concrete without the admixture can meet the vapour transmission requirements.

Hence the conclusion at present is that individual project needs and perceived risks will need to be considered in deciding whether there is benefit in adopting one of these admixtures in a concrete-alone solution or to design on the basis of a tanking membrane system.

The Use of External Tanking Membranes for Below Ground Concrete Structures

 

A significant use of external tanking membranes for below ground concrete structures world-wide is to provide protection against deterioration in aggressive ground or groundwater conditions. As with resistance against water ingress, the promoters of these admixtures make considerable claims about enhanced durability performance.

Unfortunately most projects have their durability design based not on performance, but on prescriptive rules for various exposure conditions. The application of a robust tanking membrane can make very positive statements about changing the exposure conditions the concrete will experience.

The adoption of a water permeability reducing admixture, will change, usually improving, the resistance to deterioration, but to an extent that cannot be readily defined against code or other references used for design. If we use admixture X by how much could we reduce minimum cement content or by how much increase the maximum w/c ratio on any given site. At present there is very limited guidance. This should not be taken to mean there are no situations in which any durability benefits are useful. There will be such situations, where for example applying a tanking membrane to a structure is not feasible.

Warranties For Concrete Admixtures

The admixture manufacturer offer of warranties was mentioned earlier in this note. These can outwardly be attractive in establishing confidence in the waterproofing option. In précis terms the warranty will offer to oversee the detail of waterproofing design, have some contribution to site practice and significantly, warrant that if there is a leak they’ll come back and ‘fix’ it.

On those projects that we’ve encountered a warranty in place, the arrangement appears to work to a large degree. However typical warranty documents have potentially significant issues. Returning to ‘fix’ the leaks only covers the act of grouting or patching or whatever is required. The supplier will normally be expected to be provided free (in both senses) access to the defect. This may be difficult and have significant on-cost if the leak becomes apparent only after the space has been fitted out with plant and other equipment. Leaks may not become apparent until sometime after the construction has been completed. A further common limitation is that the cost of the ‘fix’ will only be covered up to the cost of the admixture originally supplied.

These warranties may well be a positive contribution for particular projects but it is recommended that the warranty terms are vigorously reviewed.

There is hopefully a wider and more detailed debate to be had on the issues raised in this paper. There is certain to be a spread of views, experiences and expectations across the UK construction industry.

Discuss!

Newton Waterproofing Systems thank Bob Cather for his submission of this article.

For more information, read our page on Waterproofing Concrete Structures, and learn about our concrete joint and leak sealing products and our reinforced concrete structures.

With flooding set to remain a very real threat to many UK homeowners for the foreseeable future, how can waterproofing measures assist those who are recovering from flooding, as well as preparing our homes against the threat of future flood events?

Whilst the winter of 2016/17 saw most homes escape any serious flood events, for some the arrival of storms such as Doris and Ewan has acted as a firm reminder of the very real threat posed by the seemingly increasingly disruptive UK weather. For some still the events of December 2015 are also a recent, and painful memory, as a result of the havoc that storms Desmond, Eva and Frank wreaked on over 16,000 residential homes in England.

With flooding set to remain a very real threat to many UK homeowners for the foreseeable future, Toby Champion, Commercial Director at Newton Waterproofing Systems, examines how waterproofing measures can assist those who are recovering from or facing the threat of future flood events.

Cleanup

It is when the waters recede that flood victims are left with the greatest challenge – how to make flood-damaged properties fit for reoccupation quickly, and how to protect our homes from a repeat of such catastrophes in future?

Frequently, the post-flood cleanup can be as frustrating and torturous as the flooding itself, and making affected properties habitable again can take a lot longer than expected. From health and safety assessments, flood damage assessments, flood characteristic investigations and future flood risk assessments, to the stripping out of irreparable fixtures and fittings, a whole host of factors can prevent occupiers from returning to their homes.

However, one of the most onerous delays to the reinstatement and reoccupation of flood-affected properties is the unavoidable requirement to allow saturated structural walls to dry out, which can be as painfully slow as one month per inch of wall thickness. Furthermore, the process cannot begin in earnest until all contaminated finishes and organic materials have been removed and a ‘Decontaminate Building and Sanitation Certificate’ has been issued.

Either expediting or circumventing this part of the flood recovery process is therefore a crucial element in ensuring swift reoccupation of a property.

Recovery

Designing an effective and achievable flood management strategy is vital to being able speed up reoccupation, and cavity drainage systems, comprising of membranes, drainage and pumps, can be a key contributor to success.

The High Density Polyethylene (HDPE) membranes employed as part of such a system are designed with a cuspated profile, creating an air gap between the membrane and the surfaces to which it is applied. Once installed with specially sealed fixings as part of a comprehensive cavity drainage system, the membranes have two major benefits for flood-affected properties:

By providing a barrier that is completely impermeable to water, the membranes separate the damp structure from the internal environment, allowing new internal surfaces and finishes to be installed immediately. They are also permanently effective against damp, salts, staining, and moulds, just a few of the potential side effects of the drying process that can impact internal environments.

Secondly they use positive vapour pressure to ‘move’ dampness out of the property. Internal vapour pressure in the air gap created by the cuspated profile of the membrane is greater than external vapour pressure outside. The result is a vapour pressure equalisation process, occurring where internal pressure moves out to the lower pressure externally. In doing so, dampness in the external walls is moved outwards of the property.

Reoccupation And Remediation

By maintaining the status quo of the structure whilst simultaneously protecting internal environments, an effective cavity membrane system allows finishes to be applied with the peace of mind that the membrane will prolong their longevity and allow the walls to dry naturally behind. Most important of all though, is that in most cases the property can be reoccupied significantly earlier than if the walls were required to dry naturally to a point where new finishes could be applied directly.

Furthermore, when installed as part of a comprehensive Cavity Drain System that also employs suitable drainage, the system will have additional benefits beyond just providing a solution for post-flood damp proofing. Once installed, the system will assist in future-proofing the property against further flooding, forming an integral part of an overall designed flood remediation solution. By depressurising water as it enters the structure, the system is able to manage and drain it to a sump, before safely pumping it out and away from the structure, protecting both the occupants, and their possessions, inside.

The construction industry’s drive towards considering lifetime structural performance, rather than just the cost of the construction itself, is having an impact on attitudes towards product selection and implementation.

Toby Champion, Commercial Director at Newton Waterproofing Systems, considers the motivations behind this, and the part that waterproofing has to play.

Whilst consideration of a structure’s lifetime performance has always been essential, it’s only in recent years that it has developed into a critical focus. The benefits of modern technology have resulted in industry-wide campaigns to implement new processes, such as BIM, with the goal of unlocking “more efficient methods of designing, creating and maintaining”(1) structures.

The campaign has significant support, both from industry institutions that are observing “significant efficiencies and improved asset value”(2), and from outsiders, including the Government’s drive to define “cross-Government principles for setting functional requirements based on whole life value for money and centred on performance”(3).

These straightforward benefits – improved efficiency, sustainability, cost and performance – reinforce the focus on the lifetime of a structure, and new technologies such as BIM are inexplicably linked to achieving them.

Simply through its implementation, BIM creates a previously non-existent culture within which it is possible to ascertain “the consequences of design-stage decisions over life cycle performance”(2), and therefore overcome the “risk that the quest for lowest initial capital cost will take precedence.”(3)

The consequence of this therefore becomes the creation of a new “platform for more efficient and sustainable solutions… offering unparalleled benefits to clients and end-users over the lifetime of buildings and infrastructure.”(1)

“Unsurprisingly, remediation costs frequently run to many thousands of pounds, and depending on the size of the structure, sometimes into the millions.”

How Does This Relate To Waterproofing?

Frequently, either too little thought is given too late to a structure’s waterproofing requirements, or it is not credited with providing tangible benefit to the end-user. The usual consequence of either scenario is that waterproofing is either excluded, or inappropriate solutions are implemented in a last-ditch attempt to achieve a watertight structure, generally on an unrealistic budget.

However, this blasé approach can have dire ramifications, and in worst-case scenarios significant water ingress will occur, causing irreparable damage to internal environments.

In these situations, even basic remedial work is costly, and when considering the potential damage in an inhabited internal environment, consequential losses can be astronomical.

In most cases, even before completely replacing and reinstating internal finishes, it is first necessary to:

• Decant the occupiers;
• Strip out damaged fixtures and fittings;
• Successfully perform required repairs; and
• Remediate against potential future problems

Unsurprisingly, remediation costs frequently run to many thousands of pounds, and depending on the size of the structure, sometimes into the millions.

When considering these costs in light of BIM’s aim to “enable intelligent decisions… on the whole life performance of facilities”(3), the BS 8102:2022 waterproofing code of practice’s recommendation that “A structural waterproofing specialist should be appointed as part of the design team so that an integrated waterproofing solution is created”(4) becomes incredibly pertinent.

Whilst the consideration and installation of a waterproofing solution at construction stage usually adds cost to a project, it is far better to install comprehensive protection as part of a BIM-enabled, integrated and collaborative process with one eye on the lifetime performance of the structure, than it is to try and do so once the damage is already done.

References –

1 HM Government, ‘Building Information Modelling – Industrial strategy: government and industry in partnership’
2 Joint ICE – ICES – IAM Position Paper, ‘Leveraging the Relationship Between BIM and Asset Management’
3 Cabinet Office, May 2011, ‘Government Construction Strategy’.
4 British Standards Institution, March 2022, ‘Code of practice for protection of below ground structures against water ingress’.

Contiguous piles are an efficient and cost-effective means of creating retaining structures. However, while they avoid excessive excavation and assist in the control of ground movement, the risk of groundwater ingress between the piles can be significant.

Therefore, in order to preserve and maintain internal walls and finishes, it is extremely important to ensure that contiguous piles are correctly and competently waterproofed. David Bucknell of Newton Waterproofing Systems considers the best, as well as an example of the worst, methods for effectively waterproofing such a structure.

When considering the waterproofing requirements of any structure, there are two fundamental questions that must be asked before anything else:

• What is the structure in question constructed from?
• What is the expectation of the waterproofing?

It is only once the answers to these questions have been established that the Type of waterproofing can be agreed upon – be it Type A, B or C as defined within British Standard 8102:2022(1) – or a combination of two or three of these.

At Newton Waterproofing we frequently see designs that propose the application of a cuspated drainage membrane directly to the surface of the contiguous piled walls. Without question, this is an extremely dangerous practice and should never be contemplated, due to the fact that:

• There is (technically) no structure, piles could have been chosen as the construction method for a number of reasons, such as a tight construction line or in order to achieve the desired depth. However, from a waterproofing perspective contiguous piles are not, and cannot be considered as, a structure.
• Simply applying a cuspated membrane to the piles does not create Type C waterproofing or ‘drained protection’. The British Standard makes it explicitly clear as to the standards that should be achieved by a retaining structure, stating that, “the outer leaf of the exterior wall should be capable of controlling the quantity of water that can pass through it, in order not to exceed the drainage capacity of the system. Water entering a drained cavity system is regulated by the structure, so defects that might result in unacceptable leaks should be remedied before the system is installed”.
• A contiguous piled structure makes it impossible to achieve any of the three internal environmental grades, as defined within BS 8102:2022, because of the potential for large volumes of water to pass through the gaps between the piles.

Figure 1: The cuspated drainage membrane has bowed away from the contiguous piled wall, causing the complete collapse of both the inner wall and the inner spine wall.

In short, it impossible to achieve a successful waterproofing system by simply applying a drainage membrane to the piles. Such an approach is not only inadvisable in theory; in practice it can also lead to a complete structural failure, as is evident in both Figures 1 and 2.

What Should Be Done?

In the project shown in Figures 1 and 2, the aim was to achieve a completely dry and habitable Grade 3 internal environment. However, in order to achieve this, the first thing that needs to be created is an acceptable and capable structure. In the case of contiguous piles, first and foremost this means that the gaps between the piles should be of suitable dimension for the type of ground they are retaining and then grouted in order to prevent the sort of slumping that is clearly visible in Figure 2.

Correctly Designed 

With correctly designed and constructed contiguous piles in place – which, once excavated, have been well prepared – a combined approach to waterproofing protection, with two or more of the Types, is a vital consideration. This combined approach is a significant recommendation of the British Standard, especially when, as can be the case with contiguous piles, “the likelihood of leakage is high” and even more so when trying to achieve a Grade 3 internal space where “no water penetration is acceptable”.

Therefore to begin with, hydrophilic polymer membranes such as HydroBond 403 Plus provide an effective and self-healing Type A waterproof barrier. Such membranes are pre-applied to the contiguous piles as well as being laid across the floor and, once placed, the locking fleece on the internal surface of the membrane forms a mechanical bond with the cast-in-place concrete raft reinforced liner walls.

Figure 2: With the membrane cut away, it is easy to see how the earth, which should have been retained by the structure and probably carried by groundwater, has slumped to the bottom of the piles, causing the internal wall to collapse.

When placing a concrete structure that conforms to BS EN 1992(2), Type B waterproofing can also be achieved by the inclusion of waterbars at the kicker and/ or construction joints, thereby providing a combined solution of Types A and B.

Interestingly, a well-designed and well-placed reinforced concrete structure, with the inclusion of waterbars in the construction joints to preclude water, should not require the inclusion of admixtures in order to achieve Type B waterproofing. Good-quality concrete is inherently water-resistant and the addition of an admixture is unlikely to prevent leakage at the joints.

With both Types A and B waterproofing already in place, the final and failsafe barrier to water ingress is to apply Type C waterproofing internally in the form of a cavity drainage system. This method not only accepts that water could enter the structure, it does nothing to resist the ingress, instead depressurising the water upon entry and harmlessly managing it away from the structure.

Figure 3: Newton HydroBond 403 Plus is a self-healing Type A waterproofing membrane that can be applied directly to contiguous piles.

Waterproofing Design Specialists

The effective waterproofing of below ground structures always requires a well-defined strategy and contiguous piles are no different. This approach is most effectively co-ordinated by a waterproofing design specialist, a role that the British Standard suggests should be included as an essential part of the design team, to ensure that an integrated waterproofing solution is realised.

Such a specialist will be capable of devising a tailored solution to accommodate the constraints and requirements of individual projects, as well as providing the design team with the necessary information to assist with the design, installation and future maintenance of the waterproofed structure.

In the case of contiguous piles where an internal Grade 3 environment is being sought, the recommendation of such a specialist will always be for a combined approach that is correctly and competently installed, and not just a directly applied cuspated membrane.

References: 

1.  BRITISH STANDARDS INSTITUTION, BS 8102:2022. Code of practice for the protection of below ground structures against water ingress. BSI, London, March 2022.
2.  BRITISH STANDARDS INSTITUTION, BS EN 1992-3. Eurocode 2. Design of concrete structures. Part 3 – Liquid retaining and containing structures. BSI, London, 2006.

With many historic and listed buildings not benefiting from modern forms of protection, they are often subject to the detrimental effects of damp. How do you therefore maintain structural and aesthetic integrity, whilst still achieving the desired effect?

With many historic and listed buildings not benefiting from modern forms of protection, they are often subject to the detrimental effects of damp. The challenge when dealing with buildings of special architectural or historic interest is to maintain structural and aesthetic integrity, whilst still achieving the desired effect.

Meeting Listed Building Requirements

When treating damp in historic and listed buildings, it is important that any products meet with the stringent Listed Building Requirements. Many products require surface preparation techniques that are unacceptable due to the detrimental effect on the structure, which are often irreversible.

However, some products, such as damp proofing membranes, can still be sympathetically applied with little preparation and minimal fixings. Once installed, the membrane provides an impervious barrier between the damp surface and the new internal wall, preventing moisture and moisture vapour from affecting internal finishes. When supplemented by drainage, this is one of the most effective forms of protection.

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