Waterproofing Existing Basements

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Written by Warren Muschialli

British Standard Recommendations

One of the primary recommendations of BS 8102:2022 is that with any basement, at some point in its life you should expect that water pressure will come to bear against it. Although the timing of such an event cannot be predicted, this is a practical and sensible recommendation that takes into account the unpredictability of future rainfall, changes in watercourses, or even possible burst water mains in the surrounding area. In our view, it is a very brave person that bets that water will never come to bear against a basement at some point in its existence.

Not only is it not possible to predict the timing of such an event, it is also impossible to determine the amount of water pressure that will come to bear against the basement. The British Standard helps us out once again here by recommending that, in almost all cases, the designer should expect and cater for a full head of hydrostatic water pressure. In other words, that at some point the ground surrounding the basement will be saturated so that water will come to bear against the full height of the basement.

So how do you protect against such a scenario?

‘Type C’ Cavity Drain Waterproofing Explained

Amongst the three different types of waterproofing available to the designer, BS 8102:2022 defines ‘Type C’ waterproofing as “drained protection” that works by receiving leaking water into voids and spaces created by strategically positioned drainage channels and cavity drain membranes installed to the internal walls and floor of the basement. The clever design of a cavity drain system means that ingressing water is depressurised as it enters these voids before being safely removed from the property.

Because Type C waterproofing is maintainable and considered to be the safest and most reliable form of basement waterproofing, it is very often the choice of the professional waterproofing contractor and is nearly always one of the systems chosen where combination waterproofing is used to both existing and new basement structures.

The Newton CDM System is one such maintainable Type C solution. Based upon Newton’s decades of basement waterproofing experience, and comprising of a range of high quality, BBA certified cavity drain membranes and coupled with bespoke pumping systems which include battery backup systems and telemetry options, over the years the Newton CDM System has been used to safely turn hundreds of wet and damp basements into dry, habitable environments.

Where an internal block wall is to be created in front of the cavity drain system, this detail shows one example of how the waterproofing can be designed.

Newton CDM FloorDrain channels are also used above construction joints in the slab/raft in order to capture any water entering through these joints.

The Importance of Maintainable Waterproofing

The Newton CDM System employs drainage channels at weaknesses within the structure, such as joints within the floor slab and at the perimeter of the basement where the slab meets the walls, to receive ingressing water entering through these weaknesses within the structure, before safely removing the water from the building.

Water is either collected by a sump chamber where it is mechanically pumped away from the property, or where the structure is on a sloping site, removed by gravity to a collection point that is below the basement structure. Amongst the numerous benefits of using the Newton CDM BaseDrain, one of the most important is that the drainage channels are fully maintainable and so compliant with the recommendations within BS 8102:2022.

Strategically placed inspection ports not only allow the waterproofing system to be inspected and cleaned, but they also mean that critical remedial work can be performed to the Newton CDM System without the need for major disruption. This capability also ensures that another important but frequently overlooked aspect of BS 8102:2022, which dictates that the form and feasibility of remedial treatment should be considered from the very start of the waterproofing design process.

Newton Specialist Basement Contractors

Newton Specialist Basement Contractors (NSBC) are an elite group of professional structural waterproofing and damp proofing contractors who work in partnership with Newton Waterproofing Systems to provide the specifier and their clients with the highest quality products, designs and installation available in all aspects of domestic and commercial basement waterproofing.

NSBCs can take responsibility for both the design and the installation of a waterproofing system, which means that they will give meaningful, insured installation guarantees for the work that they undertake.

Technical Drawings

Newton has an extensive library of Technical Drawings that can be utilised for your basement waterproofing project, and which are available to download in both PDF and AutoCAD formats from the Technical Drawings area of our website.

Alternatively, if you would like to talk to a waterproofing expert regarding your project, our Technical team are able to provide objective advice and guidance either over the phone or by email.