Tanking refers to damp proofing walls retrospectively by creating a complete water-impermeable barrier. There are two main types of tanking methods: applying a damp proof membrane to the interior wall, or cementitious tanking where the wall is stripped and re-rendered with a cement mix. Both methods can be effective but also involve risks if not properly evaluated and applied. New materials are being developed that could provide a double protected system of interlocking waterproof panels with a cavity drain for mechanical water extraction to reduce risks.