A brief overview of basement Water Proofing of wall and floors
Repair of a structural waterproofing system: In existing properties basement water proofing is carried out from the inner wall surface. Often using a Cavity Drain Membrane as the older wall/floor masonry may be in a weakened condition as it will not put additional load on the floor and wall structure, sometimes a combination of type A & C may be used. Within its design limits, a cavity drain membrane will manage the failure of the buildings ability to resist groundwater penetration. For instance, I have found in the Edinburgh new town area the cellars floors are often well-drained and have no water table issues. This is due to their construction and the geology. A Cavity Drain Membrane system is commonly used to control the water percolating down through the pavement and porous ground above the under-pavement cellar.
New construction sites have a separate set of waterproofing problems compared with an existing building which has a history of resisting water. In a new building, you are excavating underground (and into the unknown), and the new site has a lack of site water history. Therefore, more investigation is needed. This starts with a desk study followed by a site inspection. The research helps in select materials and create a suitable specification, which needs to address any ground contamination due to past usage of the land, ground gases, i.e. Radon and potential flooding of the area due to location.
Therefore a combination of Type A and B waterproofing system is preferred, this is applied to the new structure externally, or as part of the structure and both may require a suitable maintainable land drain installed to prevent water building up on the outside and finding a defect. By combining these, you may create a tanked construction which is able to resist water penetration.
Type A: This system relies on a coating/membrane being applied to the wall/floor to make the structure resistant to the passage of groundwater. A manageable land drain should be installed to prevent water from finding a defect in an external coating or membrane and diverted to a suitable soakaway. Groundwater should not be discharged into a vested sewer.
Type B: Is the best form of the three types as the (often waterproof concrete) wall/floor construction structure is built to resistant to groundwater penetration.
Type C: Is formed out of a studded plastic membrane which manages the water entering the building. This is often used for repairing an area (this is not a tanking). It can be combined with a Type A or B to make them more repairable.
Groundwater should not be discharged into a vested sewer, but surface water can be.