Designing Basement Waterproofing Systems
Basements are susceptible to the ingress of moisture and contaminants from the ground. For this reason, a waterproofing system will usually be required. Guidance on the requirements for basement waterproofing systems is given in BS 8102:2009, “Code of practice for protection of below ground structures against water from the ground”.
The choice of waterproofing system will depend on a number of factors such as the method & type of basement construction, the depth below ground, and the proposed end use. The example designs on this website are intended to demonstrate how BS 8102 compliant solutions can be achieved for some of the most common basement waterproofing scenarios.
In addition to dampness from the ground, basements are also commonly affected by condensation issues due to moisture-laden air within the basement structure. For this reason, the waterproofing systems described in this guide will usually need to be supplemented by mechanical ventilation. A waterproofing design specialist (see below) will be able to advise on suitable ventilation options depending on the proposed end use (e.g. car parking, document storage etc...)
A waterproofing design specialist with a CSSW qualification should be consulted at the design stage. Please contact our technical department on 01403 210204 or email [email protected] for details of suitable basement design specialists in your area.
Design resillient basement structure
E.g. Reinforced concrete structure, simple shape, minimal service penetrations
Choose suitable waterproofing system
Choose a waterproofing system appropriate for the type of basement. The designs in this guide are a useful starting point.
Waterproofing design specialist
A CSSW-qualified waterproofing design specialist should be employed to draw up a detailed waterproofing design. Call 01403 210204 or email [email protected] for details of waterproofing design specialists in your area.
Specialist basement waterproofing contractor
Correct installation of basement waterproofing systems requires specialist skills - e.g. surface preparation, detailing of joints etc... Call 01403 210204 or email [email protected] for details of specialist basement waterproofing contractors in your area.
Drainage channels and sump pumps should be serviced on a regular basis.
Continuous linking between the waterproofing below-ground and the damp-proofing / cavity trays above-ground is often overlooked.
These are a weak point, so correct design and installation is important. Water bars, such as Vandex Expaseal, should be incorporated into construction joints where possible. Vandex Super and Vandex Construction Joint Tape can be used to provide additional protection.
Simplicity of Design
Corners, voids, footers, service entries etc... present increased risk when detailing and installing any waterproofing system. Minimising these features therefore helps to minimise risk.
Minimise and eliminate if possible - e.g. by taking services up and over walls to avoid penetrating the basement structure.
Basements constructed from reinforced concrete generally present a lower risk than basements constructed from blockwork as there are fewer joints.
Free Lime Control
When using a cavity drainage system (Oldroyd) a lime control agent should be applied to all new concrete surfaces to reduce the build-up of free lime (calcium carbonate) behind the membrane and in the drainage channel / pumping system.
In the examples shown in this document, Vandex Super is used as it functions as a combined waterproofing layer and lime control agent.
Pumps, Drainage and Maintenance
All of the basement waterproofing designs in this guide feature an internally applied cavity drainage membrane (Oldroyd Xv / Oldroyd Xv 20) connected to a sump system.
PCA guidance states that; a minimum of two pumps with alarm and battery back-up must be included in the sump chamber. Provision should be made for a suitable discharge method, either by means of a mechanical (Sentry™) sump pump system or appropriate discharge point.
Maintenance is essential - the Aquadrain Perimeter Drainage Channel (via access points) and the Sentry sump pumps should be serviced on a regular basis. Pump maintenance schedules can ensure the success and longevity of any system.
More information is available in the free publication: PCA Best Practice Guidance - Groundwater Pumping Stations