I have a period property. What system is best to waterproof the cellar as part of the refurbishment?
There are two approaches to waterproofing a basement internally. One method involves cementitious tanking with a waterproofing render or waterproofing slurry, such as Vandex Uni Mortar 1 (http://www.cellars.co.uk/products/waterproof-repair-vandex-unimortar1) or Vandex BB 75 (http://www.cellars.co.uk/products/tanking-slurry-vandex-bb75). This creates a barrier to the water, preventing it from entering the living space. Because the water is prevented from entering the building, water pressure can build up on the exterior of the building causing additional loading on the structure. In addition, for the cementitious tanking to be effective, it requires a good bond with the underlying substrate. Cementitious tanking is therefore only suitable for structures capable of supporting the additional loading of any water pressure and with a strong sound substrate.
Most refurbishment projects (for example, Victorian Domestic) tend to use the alternative approach of a water management system. This involves the installation of cavity drainage membranes (http://www.cellars.co.uk/products/oldroyd-cavity-drainage-products) and a suitable drainage system (usually a sump and pump - http://www.cellars.co.uk/products/aquadrain-drainage-channel-and-sump-systems). The moisture is trapped behind a polypropylene membrane (e.g. Oldroyd Xv), requiring a suitable drainage system to channel the water to an appropriate drainage point. This approach will allow water to still enter the fabric of the building but prevents it entering the living space. As the passage of the water is not blocked, there is no additional loading on the structure and minimal surface preparation is normally required. The disadvantage is that in most cases a sump and pump system is required to remove the moisture and these have to be regularly inspected and maintained.