Steve D’Arcy of Visqueen examines how revised guidance around waterproofing make it vital to appoint a ‘fit for the job’ specialist as part of the design team – a crucial factor for avoiding pitfalls down the line
Since BS 8102 was first published in 1990 it has been raising standards in the design of waterproofing below ground structures and ensuring they provide an environment that is suitable for the intended use. When revised in 2009, the document became recognised as the industry standard, and the latest revision in March this year sets to clarify key areas – one being the selection criteria for a waterproofing specialist on projects.
Giving a clear indication of those responsible for the overall waterproofing design, BS 8102:2022 makes it clear from the onset that a waterproofing specialist should be appointed as early as possible, especially when it is imparted as a contractual process. Alternatively, a waterproofing specialist may develop an outline design, which is later adopted as part of a client’s requirements and developed by a suitably experienced and qualified waterproofing specialist as a Contractor’s Designed Portion.
What makes a waterproofing specialist?
In section 4.2 of the standard, it states that a waterproofing specialist should be appointed as part of the design team so that an integrated waterproofing solution is created. Many waterproofing manufacturers, contractors, etc. deem their employees to be suitably qualified for this role when achieving a qualification such as Certified Surveyor of Structural Waterproofing (CSSW).
However, BS 8102:2022 states that the waterproofing specialist should be suitably qualified and experienced, commensurate with the type and size of the proposed project. This is where many manufacturers, contractors and specialist installers do not fulfil the requirements. For example, an employee who is new to the waterproofing industry and has recently passed their CSSW would not be recognised in the standard as a specialist. Among other things, they lack necessary ‘live’ site experience and an understanding of construction forms and sequencing.
Similarly, where a contractor has spent 20 years in the refurbishment sector, predominantly focusing on basement conversions, they lack the experience needed to design and install a large-scale new build carpark basement requiring potentially various grades of waterproofing.
In addition, a waterproofing specialist should be capable of devising solutions that accommodate the various project constraints and needs with an understanding of construction forms and sequencing.
Finally, they should be able to provide the design team with information and guidance that assists with and influences the design, installation and future maintenance of the waterproofed structure.
As such, BS 8102:2022 has become more prescriptive regarding appointing a waterproofing specialist. For some, it has not gone far enough – many would like to see an example time frame of industry experience or a demonstration in their experience with example projects in a portfolio. The document could be more exact, but we must remember the standard is actually guidance and not mandatory. In addition, it is not always true that two years’ experience is less valid than five, or a portfolio of twenty projects is more valuable than a portfolio of five projects. Quality generally prevails over quantity.
So when seeking guidance from a manufacturer or a specialist contractor, or looking to appoint a waterproofing specialist, it is vital to enquire not only about the individual’s qualification but also their experience with similar types of projects.
BS 8102:2022 clarifies the need for waterproofing to be continuous, but more importantly to link to the DPC system 150 mm above ground level. No longer should designers purely design to the full height of the retained ground. Many waterproofing designs of old where failure occurred had not fully considered this aspect. It then resulted in water ingress attributed to substructure waterproofing defects, which were in fact due to a lack of robust superstructure waterproofing/damp proofing continuity.
Once more, this type of design flaw is a direct result of a lack of experience when designing structural waterproofing in conjunction with the DPC and cavity tray systems. Ensuring this link is robust, the waterproofing specialist must also have the correct damp proofing experience.
BS 8102:2022 reinforces this point by stating that “the practicality of terminations above ground level should be assessed at an early stage within the design to ensure full integrity of the waterproofing system, compatibility with superstructure construction and continuity with the damp and/or ground gas protection system.”
As can be seen from the above a comprehensive understanding of ground gas protection systems is also a critical consideration for the waterproofing specialist. This is an extensive specialist field of knowledge itself, and requires a thorough understanding of the various materials and ventilation systems available.
In summary, the waterproofing specialist should not only meet the criteria within the standard as set above, but also have a working knowledge of damp proofing and gas protection design and detailing. These additional skills create the specialist knowledge that is capable of safeguarding continuity throughout the design of the waterproofing system.
Steve D’Arcy is technical development manager at Visqueen