With basement waterproofing being a complex business, the current British standard recommends that a waterproofing specialist is made an integral part of the design team to ensure that an appropriate solution is arrived at in each case.

BS8102:2009 is not a prescriptive standard (like the previous version), however it represents best practice which should be adhered to and has several logical provisions when you are looking to safeguard a building’s basement against water ingress for the long term. A key recommendation in the document is the inclusion of a waterproofing specialist as an integral part of the design team, who has the necessary know-how not only to apply best practice in the solution, but also to ensure that the proposed solution is what is required by the client. The standard specifically notes that this specialist can be a manufacturer of waterproofing systems with relevant experience.

The standard itself is not straightforward in terms of interpreting the exact requirements for a particular job and this bolsters the case for including a waterproofing specialist. They will not only have the knowledge to interpret the standard to ensure that the project receives the appropriate waterproofing solution but are also able to liaise with the specifier to achieve the performance level required and not be guided purely by building type, which is a risk inherent to the way the standard is presented. BS8102 identifies three main grades of waterproofing protection against both types of building use and intended use. These grades can be loosely described as ‘wet’, ‘damp’ and ‘dry’ but a more detailed description from the standard is as follows:

• Grade 1: basic utility (such as car parking, plant rooms without electrical equipment, and workshops, with some water ingress permissible)
• Grade 2: better utility (such as workshops and plant rooms requiring drier environments)
• Grade 3: habitable (including residential and commercial areas)

The complexity comes in as BS8102 also specifies the performance level required. For example, it says that Grade 1 would “tolerate some seepage and damp areas, dependant on the intended use,” but that “local drainage might be necessary to deal with seepage.” In the case of Grade 2, the standard clarifies that “no water penetration is acceptable,” but damp areas are “tolerable, although ventilation might be required.”

The issue comes if a client or specifier chooses a waterproofing solution based on their use of structure, for example a car park, and is guided by the standard to pick Grade 1 on that basis, but actually requires a higher degree of waterproofing performance due to the nature of their business or customer expectations. Also if a change of use is likely further down the line then a lower grade of waterproofing can turn out to be a costly mistake particularly as it is installed below the concrete foundations and is very challenging to alter at a later date. 

A waterproofing specialist can assist the client and specifier in navigating the standard and scrutinizing the initial proposed design, to establish whether the grade which has been specified is appropriate, and whether it will provide for their requirements going forward. The BS8102 standard also identifies three types of waterproofing protection for the structure:

• A: Barrier (a physical barrier, typically an external membrane)
• B: Structurally Integral (often enhanced with a waterproofing admixture to increase the resistance of the concrete to water and water vapour)
• C: Drained (generally a cavity drain membrane to handle limited groundwater seepage, and prevent water vapour)

As endorsed by the 2009 revision of BS8102, a specialist is the ideal member of the team equipped with the knowledge to correctly establish the expectations of the client and design team. In practice, this means obtaining design information from the engineers in charge of specifying a project’s groundworks and ensuring their expectation is aligned with that of the client.

Risk Assessment

With many projects such as healthcare buildings or major commercial buildings, housing critical areas including technology and plant as well as staff in their basements, a robust approach to preventing leaks is crucial. The key to achieving the right strategy and avoid under-specifying a basement waterproofing solution is to undertake a full risk assessment of the project. One of the key benefits of BS8102 is that it provides a framework for undertaking the risk analysis which will arrive at the appropriate solution. The standard recommends that the structural design, overall weatherproofing design, waterproofing design and construction process are considered together, as they generally interact.

As part of this essential risk assessment the standard requires a full waterproofing strategy to be prepared which involves asking the client all the right questions in order to manage their expectations. As a specialist manufacturer of all three types of waterproofing systems, GCP does this as a matter of course in combination with the information provided by the Desk Study required under BS8102 including obtaining topography and soil investigation data. Other manufacturers will typically align their guidance towards the single waterproofing type that they produce. As well as technical specialists who can analyse a specification against industry best practice and standards, the firm also has commercial specialists whose remit covers main contractors, subcontractors and specialist applicators, who can give expert technical guidance every stage of the project.

Creating a long-term solution which is ideal for a particular project requires working with trained installers, who follow the correct installation guidelines. The final part of the process is regular site visits to support the site supervisors and installation team to ensure that the waterproofing has been installed as per instructions. There are common issues and details which emerge on site which weren’t an issue at design stage but need to be addressed in the real world to prevent the defects which can result from untrained workmanship or late design changes but can be avoided with good practice.                                                    

Having successfully delivered below-ground waterproofing solutions to a huge range of international high profile projects with a zero tolerance approach to leaks, the team at GCP has demonstrated that it has the specialist expertise to deliver high performance allied to correct specification providing flexibility for change of future use. With decades of relevant experience and its wide portfolio of systems including adhesively bonded membranes, waterproofing admixtures and cavity drain membranes, GCP has provided tailored waterproofing strategies offering the highest levels of protection and extended design lives for all types of habitable basements.