BS 8102 recognises that it is essential for the success of any project involving below ground structures that strategies for dealing with groundwater, soil gases and contaminants are considered from the very earliest stages of the planning and design processes. For new structures, it is recommended that the structural design, overall weatherproofing design and construction processes are considered together as they generally interact. In addition, it is recommended that during the design process and at all stages of the construction process, the designer's specialists manufacturers, suppliers and installing contractors establish and maintain effective channels of communication. Regular and clear communication coupled with good site supervision allows variations and amendments to the design to be planned and executed without compromising the performance of the waterproofed structure.
In our experience, this "team" approach, starting from design stage, allows for successful and cost effective waterproofing and as part of the rewrite committee we were very keen for this strategy to be emphasised. A welcome inclusion to the standard now asks for waterproofing specialist to be included as an integral part of the design team to ensure that an integrated waterproofing solution is realised.
Criteria outlined in the standard are that the individual be:
Be capable of devising solutions that accommodate the various projects constraints and needs
Provide the design team with information and guidance that assists with and influences the design, installation and future maintenance of the waterproofed structure
Successful waterproofing has always been a specialist's area of expertise. The key causes of failure in our experience are poor workmanship, poor product choice for the level of waterproofing required, cheap inappropriate products substituted from those specified to get inside an unrealistic budget, and products 'shoehorned' into the specification because they may hold sought after third-party accreditation, but are not the best product for the waterproofing requirement. The inclusion of a waterproofing specialist in the early stages of the waterproofing discussions will ideally design out the above key causes of failure and provide robust and successful waterproofing projects. For this reason, we partner with an elite group of fully trained waterproofing contractors, Newton Specialist Basement Contractors (NSBC) who can fulfil the role of 'Waterproofing Specialist'. All our registered contractors offer insured guarantees for the installation and the vast majority of NSBC contractors hold PI for waterproofing design and installation giving full protection to all parties concerned.
As members of the committee on the rewrite of BS 8102 we were very keen to promote the inclusion of specialist waterproofing contractors within the project design team, which in our experience results in more robust and successful waterproofing design and installation.
The ideal waterproofing solution would be defect-free. However, it should be noted that product or workmanship defects may occur, resulting in the required internal environment is not being achieved:
Defects owing to poor quality workmanship
Defects owing to the specific properties of the materials being used
It is essential that the construction methods and materials used to realise the design are such that the defects in workmanship are: a) are avoided and b) which are generally minor, should be recognised and catered for in the design. Contingency planning for dealing with any localised defects or system failure that arise should be included as part of the overall water resisting design of the structure. In either case it is vitally important to take into account the ability of reparability of the waterproofing system and the feasibility of remedial measures assessed. The ability to repair external systems has changed the way professional waterproofing contractors can now guarantee external waterproofing projects and highlights the practical nature self-healing 'Type A' products such as Newton 403 HydroBond, and the maintainability of Type C drained protection systems such as the Newton CDM System.
BS 8102 advises that a risk assessment is carried out, to determine the external environmental conditions. As a part of the risk assessment it is also suggested to perform a Desk Study in accordance with BS 5930 and BS EN1997:
To assess the geology and hydrogeology, including soil permeability, flood risk, radon, methane and other ground gases and contaminates. (e.g. chlorides and acids)
To assess the topography of the surrounding ground in relation to the below ground structure
To establish the likely highest level of the water table and the potential for the occurrence of a perched water table; and
To identify any missing ground and ground water information which should then be obtained by undertaking a site investigation in accordance with BS59230 and BS EN1997
The drainage characteristics for analysis of the soil should be determined in accordance with BS 8004
Taking all the information above on board allows the design team to prepare the most robust waterproofing details to provide the environmental grade that they are seeking to achieve. However, even with all this information, it is a brave individual who seeks not to protect the structure by believing that water will not come to bear against it. Periods of prolonged and heavy rainfall are becoming more prevalent and the design must be able to deal with all eventualities, including burst water mains. It is prudent therefore, that designers deal with the potential for full height of ground water to be bearing against the structure, to ensure that their designs are robust enough to deal with all possibilities. It is worth noting that the standard states that: 'Even when the site investigation indicates dry conditions, the risk of some waterlogging in the future should be assumed' and that: 'Even in a permeable subsoil, groundwater requires time to drain away and this can result in limited pressure periodically coming to bear against the structure'.
To sum up, the revision of the British Standard in 2009 included new technologies available to waterproofing designers, and included the suggested for a 'packaged' waterproofing design involving a qualified design team, and this has addressed the previous issues which resulted in many failures of waterproofing systems, namely poor workmanship and poor choice of materials. These changes allow for manufacturers, specifiers and end clients peace of mind that waterproofing can be performed constantly to a managed high standard so that as the use of basement space becomes more and more popular, the correct combination of materials and planning is available to get it right the first time.
Our staff are able to provide guidance for projects of all sizes, whether you require some general advice about damp or waterproofing, or support with technical drawings and specifications.
Newton Specialist Basement Contractors (NSBC) are an elite group of professional structural waterproofing and damp proofing specialists who work in partnership with us to provide clients with the best products, design and installation.