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Below Ground Waterproofing / Tanking
All structures that are partially earth retaining or fully below ground are likely to be subject to some degree of water ingress during their lifetime. During periods of sustained or heavy rainfall, the ground surrounding the structure becomes saturated with water. The depth of water surrounding the structure creates water pressure relative to the depth of the saturation and the depth of the structure below the ground. Once the pressure is greater than the resistance of the structure, leakage or flooding occurs. It is therefore necessary to carry out waterproofing of areas below ground level (damp proofing is not suitable).
Areas below the ground are often not used to their full potential and are therefore regarded as 'dead space'. However, Anglian Tectonics is able to supply and install systems that can be used to waterproof below ground walls and floors, in order that they can be converted into dry habitable living areas. This system can also be adapted for use in new build structures. All projects are specified differently, in order to meet the requirements of the client and comply with BS8102: 1990. (This is the British Standard for waterproofing of structures below the ground).
By using the correct waterproofing systems, below ground areas (such as cellars & basements) can be transformed into dry habitable living areas, such as guest rooms, kitchens, studios, playrooms, etc. Whatever the use, a refurbished basement or cellar is likely to add value to the property. The type of work normally required is commonly referred to as 'tanking' or 'structural waterproofing'.
The main system used by this company for waterproofing below ground areas is known as a Cavity Drainage Membrane (C.D.M). This system is able to deal with aggressive water ingress to all earth retaining structures and is complimented with various drainage and ancillary products.
The cavity drainage membrane is formed High Density Polyethylene. The membrane is fixed to the walls with specially designed plugs. The cavity drainage membrane is not designed to hold back water pressure, but de-pressurises water ingress allowing water to run freely behind the membrane. The system should be designed to remove such water ingress. A complete system would involve laying the membrane across the floor. The membrane alone should not be relied upon and specially designed drainage channels should be cut into the floor to facilitate movement of the water and this should be directed to a sump and pump or suitable gravity drainage.
The drainage channel is suitable for both remedial and new build work. The channel is designed to sit in the floor at the junction of the wall, which is generally the point of water ingress in the majority of structures. Water entering the below ground area is intercepted by the channel and diverted to the sump chamber or gravity drainage.
The pump installation will vary dependent on site conditions. The pumps installed are made from epoxy coated high-grade cast iron and are fitted with a vertical float switch. The sumps are fitted with a high water alarm and we can also offer an additional battery back up pump, which will provide protection in the event of a power cut.
Once the membrane has been installed to the walls and floor they can be closed in. The floor membrane can be protected with either a sand/cement screed of at least 50mm or by fitting a floating chipboard floor.
The membrane fixed to the walls is normally finished with a plasterboard dry-lining system. Timber battens or preferably a metal stud frame can be used. The choice of lining would be dependent on the use of the room. It is often beneficial to install any electrical wiring or pipe runs within the framework prior to the closing in of the wall frame.
Once the floor and wall finishes have been installed, further items can be added such as skirting boards, architraves, etc, turning what was originally a damp unusable space into an area suitable for use as a playroom, study, bedroom or kitchen.
The Cementitious Structural Waterproofing System is an alternative system and is based on a specially designed slurry powder, which is mixed and applied to the damp surface with either a brush or trowel. Once applied the slurry forms a strong bond with the masonry, blocking the passage of water and becoming an integral part of the structure. This system can be used alone or if necessary in conjunction with the Cavity Drainage Membrane System.
The Cementitious Structural Waterproofing System withstands high water pressure and is suitable for use in complex and intricate structures. The Cementitious Structural Waterproofing System is complemented by further ancillary products, which deal with problems at the wall/floor junction and other commonly found situations. This company also uses further waterproofing systems such as epoxy resins.
The type of waterproofing used in below ground areas is often dependent on the structure and site which has to be dealt with. The actual proposed use of the area is also an important factor. Each building will have its own conditions and our surveyors and estimators would give expert advice on the individual requirements of the structure.
Full consideration is given to guidance, design and good practice, as described in BS8102. This is the British Standard for waterproofing structures below the ground. Those designing a new earth retaining structure or, indeed, upgrading an existing structure, should be aware of the requirements of BS8102.
Anglian Tectonics are members of The Structural Waterproofing Group. The S.W.G was formed to increase recognition of the quality of waterproofing products and services available from its members, and to provide a continuous training programme for member companies.