Basement tanking is a technique used to waterproof any structure or property that is built below ground level. Waterproofing is necessary when a structure sits below ground level to combat the build-up of groundwater around the edge of the building. This water can easily penetrate the porous brick walls of a basement or cellar and result in flooding or, if the water build-up is significant enough, it can result in hydrostatic water pressure and decreased stability of the basement walls.
In short, basement tanking is necessary to keep water from entering your basement or damaging the structural stability of your underground structure. Without the appropriate waterproofing, structures can suffer from extensive damp and mould problems - if they don’t flood outright.
Any basement tanking in the UK is bound by British Regulations (BS8102:2009) and as a result, it can be split into two distinct remedial categories: Type A Waterproofing (cementitious tanking) and Type C Waterproofing (membrane tanking). Both waterproofing techniques are effective but depending on your individual property and situation, it might be more efficient, effective or reliable to use one method over another. The Type B Waterproofing category relates to building fabrics that are prefabricated to provide damp/water barriers, generally introduced during property construction and thus not an area of works we engage in.
Cementitious Tanking is the simpler and more common waterproofing option and involves creating a simple barrier that stops groundwater from entering or affecting your basement or cellar.
The first stage of the installation process is the preparation of the internal walls; they are stripped back to their base material (usually brick) before new materials begin to be applied. After the base material is exposed, a sand and cement render splatter coat is applied, followed by a multi-coat render, both of which are combined with the most suitable waterproofing agent for the project.
The agents used for Cementitious Tanking vary greatly, from waterproof renders with Sika additives, to slurries to epoxy resins. The agent that we use for our own basement tanking work varies depending on the individual project as some situations can benefit from specific material advantages. Similarly, you might have a specific finish in mind which will help lean towards a certain waterproofing material.
The render applied to the walls creates a watertight seal which prevents any water from entering the property or affecting the internal face of the wall. Usually, this waterproofing method is concluded with a skimmed plaster finish, but it can also be left in its raw render state, too.
Cementitious Tanking is usually a suitable waterproofing solution unless the walls of your basement are already suffering from fragility or instability. Similarly, if the geography of the area indicates that your basement will be exposed to very high levels of groundwater, then Type C Waterproofing is often a more effective basement tanking solution.
Membrane Sealed Tanking or Water Management System: Type C Waterproofing
Membrane Sealed Tanking is a more complex waterproofing system that involves the implementation of a membrane to trap any ingressing water before pumping it away.
Installation and How Type C Waterproofing Works
The process to implement a Membrane Sealed Tanking system begins with clearing the internal walls of any loose, friable and organic material prior to the installation of the membrane on all applicable walls, floors and ceilings, using specialised plugs. Any necessary piping or plumbing is sealed to the membrane using pre-prepared plugs or plyboard to ensure nothing is disrupted by the basement tanking process. Afterwards, perimeter channels are installed around the base of the walls or floor, leading to a sump and pump system which will carry the water away from the property.
In the same manner as Type A Waterproofing, Membrane Sealed Tanking installations are usually finished using high-quality plasterboard so that you can decorate your new space with ease.
This basement tanking system is designed to trap any water and guide it into the perimeter channels where it is pumped away safely into the drains. The key difference between Type C Waterproofing and Type A Waterproofing is that Type C removes the water, whereas Type A simply stops it from entering the basement structure.
When is Type C Waterproofing Suitable?
Membrane Sealed Tanking basement water systems are more expensive and complex types of basement repair but also more reliable, particularly for handling unpredictable levels of water. Furthermore, this basement waterproofing technique puts no additional strain on the building’s structure, is easily maintained and often produces less waste or disruption during the installation process.
Saying this, Type C Waterproofing isn’t always the best value for money and we always advise that you instruct a professional survey to confirm the best option for you.
Boasting over 16 years' experience, the knowledgeable team at Garratt’s Damp & Timber is perfectly placed to survey your property and advise you on the best course of action. Our basement tanking solutions come with a 10-year guarantee, the industry standard, so that you are 100% confident the work will last the duration.
We strive to offer honest, no-nonsense advice that works around you and your needs, which is why we offer a completely free survey from one of our qualified surveyors (CSSW: Certificated Surveyor in Structural Waterproofing), complete with a post-survey report of everything we have found. We will answer all questions, such as how much does it cost to tank a cellar, anything you would like to know about the basement waterproofing membrane as well as how long the renovation works are expected to take.
We pride ourselves on offering impartial advice and bespoke service, so please don’t hesitate to get in touch on 0208 535 7536 if you have any questions or would like to book a survey.