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Written by Warren Muschialli

Cavity drain waterproofing (defined as Type C (drained) protection) relies heavily on a properly designed and installed drainage system. Because effective water management is critical for the success of a cavity drain waterproofing system, understanding how to correctly install and maintain the drainage system is essential for achieving long-lasting basement protection.

This guide explores the comprehensive process of installing a cavity drainage system, focusing on best practices and key considerations for successful implementation.

Understanding Cavity Drainage Systems

cdm-inspection-port

Before diving into installation procedures, it’s important to understand what constitutes a cavity drainage system. The Newton CDM System, an example of a comprehensive Type C, cavity drain waterproofing solution, comprises four main components:

  • BBA approved cavity drain membranes
  • Drainage channels
  • Pumping systems
  • Pump control and telemetry systems

When designing a Type C system, each component plays a vital role in creating an effective water management solution.

What Makes Cavity Drainage Systems Different from Other Forms of Waterproofing?

Cavity drainage systems are classified as ‘Type C’ waterproofing by the British Standard for waterproofing, BS 8102:2022. Unlike Type A and Type B waterproofing solutions, Type C offers a maintainable solution that manages water ingress rather than attempting to block it.

Instead, the Type C system receives water at the point of entry and uses drainage to direct it to a safe point of removal. This approach makes cavity drain waterproofing one of the most reliable and safe forms of below-ground waterproofing.

Pre-Installation Assessment

If you are planning on using a cavity drainage system as part of your overall waterproofing solution, there are some key factors that must be considered during the design of the system, to ensure a successful installation:

Injection Resin Packer Installation

  • System Design Considerations: The design phase must account for required drainage capacity, optimal channel positioning, and pump system specifications. Maintenance access points need to be strategically planned, and the system must be designed to integrate effectively with existing structures.
  • Site Evaluation: A thorough site assessment is also crucial before beginning any installation work. This includes examining existing water ingress points, potential ground water levels, and any surface water considerations. The structural condition of the basement must be evaluated and potential leaks sealed with a Type A tanking membrane or resin injection to ensure that the volume of water entering the structure does not overwhelm the Type C system. Uniquely, Type C systems are required by BS 8102:2022 to be maintainable, so access into the drainage system also needs to be carefully considered. Understanding these factors helps determine the most effective system design and installation approach.

Installation Process

  • Surface Preparation: The first step in installation involves thorough surface preparation. All surfaces must be cleaned and structural defects or leaks should be repaired.
  • Membrane Installation: Selecting and installing the appropriate membrane type is crucial for system effectiveness. The membrane must be securely fixed to walls and floors using appropriate fixings, with all joints and penetrations properly sealed. Ensuring that the drainage channels always collect the water captured by the membrane ensures proper water management throughout the system.
  • Drainage Channel Installation: Installing drainage channels requires precise positioning and execution. Channels are always installed to the perimeter of the area being waterproofed, as well as across any structural weaknesses such as construction joints in the concrete slab or raft. Additional cross-floor drainage is used to reduce the distance that collected water needs to flow to the discharge point, whether that be a pumping system or removal by gravity on sloping sites.
  • To ensure long-term serviceability and maintainability, accessible and useable access points must be incorporated at strategic locations so that inspection by camera and removal of blockages and debris are possible throughout the whole drainage system.
  • Pumping System Integration: If there is no safe means of natural drainage, then the sump and pump system serves as the collection and removal point for water within the cavity drainage system. Proper positioning of the sump chamber/s, installation of primary and backup pumps, and connection to drainage channels must be executed with precision. Control systems, battery back-up systems and alarms and monitoring systems should also be included to ensure reliable operation and to provide early warning of any issues.
  • Testing and Verification: Comprehensive testing of all system components is essential. This includes checking connections and ensuring proper sump operation. Rising main pipe and fittings should be installed correctly using glued joints and should be inspected before client handover. Detailed installation documentation should be maintained for future reference.

Ongoing Maintenance Requirements

The pumping system must be robust and reliable, incorporating both primary and backup pumps, battery backup systems, and high-level alarms. However, the long-term success of a cavity drainage system depends on regular maintenance.

The pumping system should have its first service within 3 months of being commissioned, and at this point a future service schedule should be agreed between the service engineer and the client. The servicing and maintenance of Type C systems should be carried out by trained, competent service engineers, with a good knowledge of Type C waterproofing and access to the specific details of the installed system to ensure its continued effectiveness.

Integration with Other Waterproofing Types

Technical Drawing showing Integral Waterproofing (Type B)

British Standard BS 8102:2022 recommends combining different waterproofing types for improved protection. Depending on the scenario, the Newton CDM System can be effectively integrated with the HydroBond Type A external, HydroCoat Type A internal and HydroTank Type B integral waterproofing systems to provide superior protection against water ingress.

Professional Installation and Support

Working with qualified contractors is essential for successful system installation. As well as our comprehensive technical support, including design assistance, installation guidance, and ongoing maintenance advice, our nationwide network of Newton Specialist Basement Contractors (NSBCs) work in partnership with us to provide the highest quality products, design, and installation in all aspects of domestic and commercial basement waterproofing, supported by their own installation guarantees. This professional network of contractors ensures systems are installed to the highest standards and maintain their effectiveness over time.

Quality Assurance and Testing

Post-installation testing is crucial for verifying system effectiveness. This includes comprehensive flow testing, pump operation verification, and alarm system checks. Proper documentation of all testing and installation details provides a valuable reference for future maintenance and modifications.

How Can Newton Waterproofing Help You?

With proper installation and maintenance, a cavity drainage system provides the most reliable and maintainable solution for basement waterproofing. Professional installation by qualified contractors, combined with regular maintenance, is key to ensuring your system’s long-term effectiveness and protecting your investment in below-ground spaces.

Contact Newton Waterproofing’s technical team today for comprehensive support in designing and installing your basement drainage system. Our specialists will ensure your installation meets all relevant standards and provides reliable, long-term protection for your below-ground space.

Speak to our friendly, expert team

Our staff are able to provide guidance for projects of all sizes, whether you require some general advice about damp or waterproofing, or support with technical drawings and specifications.


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