The type of treatment is required where external ground levels are higher than internal floor levels where walls are totally earth retaining, for example, within basements and cellars, subterranean vaulted areas may be completely enclosed by earth or where adjacent structures or properties are constructed at different levels. The theory of structural waterproofing is to provide a water impervious, dry decorative surface initially, retaining moisture or dampness or indeed free running water within the adjacent ground area. This type of structural waterproofing is often required where adjacent ground levels are slightly higher than internal floor levels and excavation or lowering of these levels is not practically possible. Waterproof rendering can also be used in other situations where penetrating dampness cannot be avoided.
Site conditions and the structure itself will dictate the waterproofing specification. The systems most frequently used by Anchor Property Care are multi-renders, cementitious coatings, and cavity drainage membranes.
Multi-coat renders are cementitious renders modified with chemical additives and applied to the structure in several layers. Cememtitious coatings are pre-mixed compounds supplied in powder form. Once mixed with water on site, the waterproofing slurry is then applied in one or two coats to a previously applied base coat, which can then be covered by a further render coat creating a ‘sandwich’ effect.
Water proofing structures below ground such as basements, cellars and other structures are required to comply with BS 8102:2009, the British Standard for water proofing structures below ground. These fall into 3 categories, which include ‘barrier’, ‘structurally integral’ and ‘drained’ protection and divided into 1, 2 & 3 grades dependent upon the proposed use of the structure. In the majority of cases where a cellar or basement is converted or upgraded, a completely dry environment is required hence no moisture ingress and humidity control and/or ventilation is required to control the environment.