the expert - bs 8102 - esicms.esi.info/media/documents/timbe_bs8102_ml.pdf · 2016. 6. 21. · the...

The new revision of BS 8102 and how it may affect your waterproofing designThe new revision of BS 8102 and how it may affect your waterproofing designThe new revision of BS 8102 and how it may affect your waterproofing designThe new revision of BS 8102 and how it may affect your waterproofing design

Although the principles contained within the Code are still sound, after nearly twenty years, BS 8102:1990 Code of Practice for Protection of Structures against Water from the Ground was overdue for revision. First of all, the Code is now called BS 8102:2009 Code of Practice for Protection of Below Ground StructuresBS 8102:2009 Code of Practice for Protection of Below Ground StructuresBS 8102:2009 Code of Practice for Protection of Below Ground StructuresBS 8102:2009 Code of Practice for Protection of Below Ground Structures against Water from the Ground. Relevant ChangesRelevant ChangesRelevant ChangesRelevant Changes Although the original BS 8102 principles are maintained, there are several changes and additional points in the revised code which significantly enhance the original. Of these, the following are most pertinent: 1. Design team to include a waterproofing specialist. 2. Assume water pressure to the full height of the basement. 3. Meaning of the term “defects”. 4. Grade 4 environment has been removed. 5. Type C now includes cavity drainage membrane. 1) Waterproofing Specialist1) Waterproofing Specialist1) Waterproofing Specialist1) Waterproofing Specialist In section 4.2, The Design Team, the code recommends “A waterproofing specialist should be included as part of the design team so that an integrated waterproofing solution is created. The waterproofing specialist should:

• be suitably experienced;be suitably experienced;be suitably experienced;be suitably experienced; • be capable of devising solutions that accommodate the various project restraints be capable of devising solutions that accommodate the various project restraints be capable of devising solutions that accommodate the various project restraints be capable of devising solutions that accommodate the various project restraints and needs;and needs;and needs;and needs; • provide the team with information and guidance that assists and influences the provide the team with information and guidance that assists and influences the provide the team with information and guidance that assists and influences the provide the team with information and guidance that assists and influences the design, installation and future maintenance of the waterproofed structure.”design, installation and future maintenance of the waterproofed structure.”design, installation and future maintenance of the waterproofed structure.”design, installation and future maintenance of the waterproofed structure.” It goes on to say “…The waterproofing specialist could be a manufacturer or material supplier, provided that the manufacturer/supplier has the relevant expertise”

The new revision of BS 8102 and how it may affect The new revision of BS 8102 and how it may affect The new revision of BS 8102 and how it may affect The new revision of BS 8102 and how it may affect your waterproofing designyour waterproofing designyour waterproofing designyour waterproofing design

Meet “The Expert” “The Expert” “The Expert” “The Expert” This man of mystery is an experienced waterproofing expert with a wealth of knowledge to share. In this article we look at BS 8102:2009 BS 8102:2009 BS 8102:2009 BS 8102:2009 and how the changes affect waterproofing design.

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The code is not specific about what the qualifications of the Waterproofing Specialist, which is why the Property Care Association (with the approval of the BS 8102 committee, as well as the Basement Information Centre) is putting together a Waterproofing Design Consultant qualification. Once there are sufficient Design Consultants, design teams will be able to call on these Consultants to assist in the waterproofing element of the design. 2) Water Pressure2) Water Pressure2) Water Pressure2) Water Pressure It is in this area that BS 8102 has the most significant change. Whereas it used to say that you had to anticipate a head of water of ¾ the depth of the basement, or 1m (whichever is the greater), it now separates groundwater into two categories: Hydrostatic head Saturated ground The hydrostatic head (from a water table, whether natural or perched) is there for the purpose of the structural engineer, who has to design the structure to resist this water pressure. The code gives more latitude to the engineer to interpret the maximum head he needs to design for, and gives guidance on these matters. From the waterproofing point of view, the code is now quite clear: regardless of the decision made by the structural engineer as to the position of the water table, the waterproofing specialist has to allow for some water pressure (from saturated ground) to the full height of the basement.

The code does not specify the source of the water. The most obvious is heavy and persistent rainfall, but it could just as easily be burst water mains, damaged drains or rainwater goods, etc.


Diagram showing water pressure


3) Defects3) Defects3) Defects3) Defects The term “defects” has long been a contentious issue, as the common perception of “defects” is “poor workmanship”. However, the code now recognises that there are two types of defect: Defects owing to poor workmanship or inappropriate use of materials; Defects owing to the specific properties of the materials being used. Whilst defects owing to poor workmanship can be avoided by proper design, planning and supervision, and the use of skilled workmen, the code now recognises that the defects inherent in the system because of the properties of the materials being used can not necessarily be avoided. Consideration must be given, at design stage, to the effects of defects, and how they can be overcome should they result in an unacceptable situation. From this point of view, there is no difference between the new and old codes, but the issue is now described in a much clearer and unambiguous manner.


A failure in concrete waterproofing


4) Internal Environments4) Internal Environments4) Internal Environments4) Internal Environments Table 1 of the old code has been replaced with Table 2. Table 2 Grades of waterproofing protectionTable 2 Grades of waterproofing protectionTable 2 Grades of waterproofing protectionTable 2 Grades of waterproofing protection

This table is similar, in that Grade 1 still permits some seepage as long as the area remains fit for purpose, but no seepage is permissible for Grades 2 or 3. Table 2 also omits Grade 4, as it is simply Grade 3 with enhanced ventilation, air condition or dehumidification.

GradeGradeGradeGrade Examples of use of structure (a)Examples of use of structure (a)Examples of use of structure (a)Examples of use of structure (a) Performance levelPerformance levelPerformance levelPerformance level

1111 Car parking; plant rooms (excluding electrical equipment); workshops.

Some seepage and damp areas tolerable, dependent on the intended use. (b) Local drainage might be necessary to deal with seepage.

2222 Plant rooms and workshops requiring a drier environment (than grade 1); storage areas.

No water penetration acceptable. Damp areas tolerable; ventilation might be required.

3333 Ventilated residential and commercial areas, including offices, restaurants etc; leisure centres.

No water penetration acceptable. Ventilation, dehumidification or air conditioning necessary, appropriate to the intended use.

(a)(a)(a)(a) The previous edition of this standard referred to Grade 4 environments. However, this grade has not been retained as its only difference from Grade 3 is the performance level related to ventilation, dehumidification or air conditioning

(b)(b)(b)(b) Seepage and damp areas for some forms of construction can be quantified by reference to industry standards such as the ICE’s Specification for piling and embedded retaining walls.



Type CType CType CType C The original code recognised Type C as the most reliable system, but it did not include the currently used cavity drainage membrane systems. The new code recognises the place that membranes have in Type C, and includes a great deal more detail on their installation, as well as accentuating the importance for ongoing maintenance. The three different types of system quoted in BS 8102 are : • Type A: Barrier ProtectionType A: Barrier ProtectionType A: Barrier ProtectionType A: Barrier Protection • Type B: Structurally Integral ProtectionType B: Structurally Integral ProtectionType B: Structurally Integral ProtectionType B: Structurally Integral Protection • Type C: Drained ProtectionType C: Drained ProtectionType C: Drained ProtectionType C: Drained Protection


Cavity Drainage Membrane System


Conclusions Conclusions Conclusions Conclusions Once architects have taken on board the need for a waterproofing specialist on the design team, defective designs should be reduced. Furthermore, where unacceptable leakage occurs as a result of defects, it should be possible to undertake remedial work without having to completely strip out the basement, as is often the case at the moment. Furthermore, it should be much easier for waterproofing specialists to comply with the code, as it is clearer, less ambiguous, and more flexible in terms of what can and cannot be done. Finally, it is worth noting that it is not a statutory requirement to comply with this (or any) BSI code. However, when things go wrong and law suits start flying, the first thing the courts look at is compliance with relevant codes. If a design does not comply with the appropriate code, the designer will need to justify why it does not comply. In short, it is easier to comply with the relevant codes in the first place and, with this new code, it should be easier.

For Further information on Basement Waterproofing and the solutions available For Further information on Basement Waterproofing and the solutions available For Further information on Basement Waterproofing and the solutions available For Further information on Basement Waterproofing and the solutions available visit www.timberwise.co.uk or call 0800 99 11 00visit www.timberwise.co.uk or call 0800 99 11 00visit www.timberwise.co.uk or call 0800 99 11 00visit www.timberwise.co.uk or call 0800 99 11 00

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the expert - bs 8102 - esicms.esi.info/media/documents/timbe_bs8102_ml.pdf · 2016. 6. 21. · the...

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