What is BS 8102? Well, if you’re dealing with a reputable basement waterproofing specialist, it’s a name that you’re likely to hear often.
It is essentially a document that outlines best practice when planning a basement waterproofing scheme, advising the designer on the various methods of waterproofing available and the correct way to ‘specify’ them for contractors, ensuring a successful and long-lasting installation.
Contractors are not legally bound by British Standards such as BS 8102 but, should there be a failure in the system due to shortcomings in the design, this is the ‘code of practice’ that would probably be referred to in any litigation proceedings.
The document was updated in 2009 from a previous version written in 1990, to reflect the popularity in residential basement conversions, an increase in deep urban constructions, and numerous advances in basement waterproofing technology. It also takes a more detailed look at the risks involved with below-ground spaces and how best to mitigate them in practice.
The purpose of BS 8102
The main goal behind BS 8102 is to guide designers in assessing the potential risk of water ingress to a below-ground structure and identify the most appropriate and adequate ways to safeguard against it. It identifies three types of protection – A, B and C – aimed at achieving different internal environments, suited to different uses of the underground space (for more information on the three types of protection, download the National House Building Council’s guide to basements and waterproofing).
There are two main threats to the effectiveness of a basement waterproofing system, namely poor workmanship and/or defects caused by using materials that are inadequate for the job. BS 8102 outlines ways to negate such issues within the design scheme, and incorporate opportunities for simple remedial measures in the unlikely event that a defect still occurs.
Besides advising designers to carry out an assessment identifying the likely risks of water ingress to an underground structure, BS 8102 also recommends that a desk study is undertaken, observing BS 5930 and BS EN1997, which covers:
- geology and hydrogeology, including soil permeability, flood risk, radon, methane and other gases and contaminates present in the ground (e.g. chlorides and acids) – follow this link for our article on the risks of radon in basement conversions.
- topography of the surrounding land (i.e. its geographical features) in relation to the underground structure
- the highest likely level of the water table and the potential for a perched water table
- any missing ground / ground water information, to be ascertained by undertaking a site investigation, observing BS 59230 and BS EN1997
- analysis of the soil for drainage characteristics, to be determined in accordance with BS 8004
Prepare for the worst
Taking account of the considerations above, the designer will be in a position to specify the most appropriate basement waterproofing system to achieve the required internal environment type. With any below-ground structure, however, there is always an increased risk of water ingress in exceptional circumstances, such as a burst water main or – increasingly often – a flash flood and, therefore, we would recommend that such ‘worst case’ scenarios are accounted for in any plans.
Besides the advice described above, BS 8102 also directs designers to design structures to ‘full head’ in earth retaining situations where:
- no detailed geological or hydrogeological information is available
- soil investigations are inconclusive with regards to groundwater
- ground drainage characteristics are unreliable
- internal and/or external drainage measures are unreliable, unmaintainable and/or infiltration cannot be controlled
Designers should also remember that, even when comprehensive information is available regarding the site, it is their responsibility to specify measures to protect the structure against other sources besides underlying water tables. These can include:
- the inflow of surface water, ranging from rainwater to wastage from burst water mains
- water pressures acting on the external retaining wall system
- water pressures below the slab base
A successful waterproofing design should result in a system that can withstand a pre-determined head of water, or control the water before it reaches the structure.
The purpose of BS 8102 is to direct designers in making decisions that will result in successful basement waterproofing systems, capable of withstanding even the worst circumstances of water pressure and presence in the surrounding area. Should anything go wrong down the line, the system should allow for simple remedial measures that make minimal demands on time and money.
It is a code of practice that holds benefits for designers, specifiers, contractors and homeowners and we, at the BWA, wholeheartedly recommend that customers deal exclusively with companies that uphold its directions.