Sikadur Combiflex 930/933 Expansion Joint Waterproofing System
The Challenge
The reservoir structure required specialist waterproofing treatment to existing expansion joints in order to maintain operational integrity and prevent water ingress or leakage.
Key challenges included:
- Movement Joint Performance: The waterproofing solution needed to accommodate ongoing structural and thermal movement without failure.
- Potable Water Compliance: All materials and installation methods had to comply with DWI Regulation 31 requirements for use in contact with clean drinking water.
- Substrate Preparation Standards: Existing concrete joint surfaces required meticulous preparation to achieve the necessary bond performance and long-term durability.
- Controlled Working Environment: Works were undertaken within a sensitive water industry asset requiring strict contamination prevention and environmental controls.
- Application Precision: Correct installation sequencing and curing conditions were critical to achieving a fully bonded waterproof seal across all joint interfaces.
The Importance of Expansion Joint Waterproofing
Expansion joints within clean water reservoirs are critical components that accommodate structural movement while maintaining watertight integrity. Failure of these joints can result in:
- Water leakage and loss of containment
- Risk of contamination ingress
- Concrete deterioration and reinforcement corrosion
- Operational disruption and costly repairs
- Non-compliance with potable water regulations
TSM’s waterproofing solution ensured the reservoir joints remained flexible, durable, and fully compliant with water industry standards.
The Solution
TSM implemented the Sikadur Combiflex 930/933 waterproofing system through a carefully controlled installation process designed to maximise adhesion, flexibility, and long-term performance.
Phase 1 – Surface Preparation & Joint Preparation
Comprehensive preparation works were undertaken to ensure the substrate achieved the required cleanliness, profile, and condition for resin bonding.
Mechanical Surface Preparation
Existing joint areas and surrounding concrete surfaces were mechanically prepared to remove contaminants, laitance, and weak material. This created a sound substrate capable of achieving optimal adhesion with the waterproofing system.
Joint Cleaning & Detailing
Expansion joints were thoroughly cleaned and prepared to ensure all interfaces were free from debris, moisture, and contamination prior to application. Particular attention was given to edge detailing to ensure continuity of the waterproof seal.
Inspection & Verification
Prepared surfaces underwent visual inspection and condition checks prior to installation to confirm suitability in accordance with manufacturer requirements and project specifications.
Phase 2 – Sikadur Combiflex 930/933 Installation
Resin Bonded Waterproofing System
The Sikadur Combiflex 930/933 system was installed directly onto the prepared concrete substrate, forming a resin molecular bond with the parent concrete structure.
This created a fully bonded waterproof joint capable of accommodating structural movement while maintaining long-term watertight integrity.
Flexible Expansion Joint Protection
The system’s highly elastic properties allow the joint to absorb movement caused by:
- Thermal expansion and contraction
- Structural settlement and vibration
- Operational loading conditions
- Long-term concrete movement
This flexibility significantly reduces the risk of joint failure and future water ingress.
Potable Water Regulatory Compliance
The installed system complies with Water Supply (Water Quality) Regulations 2016 Regulation 31 and has been assessed by the Drinking Water Inspectorate for use in contact with potable water.
This ensured the completed installation maintained full operational and regulatory compliance within the clean water environment.
Handling Project Complexities
Water Industry Safety & Environmental Controls
All works were carried out under strict site-specific water industry procedures designed to prevent contamination risks and maintain safe working conditions throughout the project duration.
Manufacturer Compliance
Installation was completed in strict accordance with Sika manufacturer specifications, technical data sheets, and approved installation procedures to ensure full system performance and warranty compliance.
Controlled Material Handling
Materials were carefully stored, mixed, and applied within controlled environmental parameters to maintain product integrity and achieve the required curing performance.
Quality Assurance
Each stage of preparation and installation underwent inspection to verify:
- Substrate suitability
- Correct joint detailing
- System adhesion and continuity
- Application quality and curing performance
- Compliance with potable water requirements
Environmental & Regulatory Considerations
Working within a clean water reservoir environment required rigorous environmental management and contamination prevention measures throughout all stages of the works.
TSM ensured:
- Controlled preparation and cleaning procedures
- Careful handling of materials within potable water environments
- Compliance with DWI and water authority standards
- Strict adherence to Water Supply (Water Quality) Regulations 2016 Regulation 31 requirements
The completed waterproofing system provides a durable long-term solution, reducing future maintenance requirements and supporting sustainable asset management within the water sector.
Project Outcome
The clean water reservoir expansion joints were successfully waterproofed using Sikadur Combiflex 930/933 system, delivering a durable, flexible, and fully compliant solution for long-term operational performance.
Post-completion inspections confirmed:
- Fully prepared and compliant concrete substrates
- Successful installation of the Sikadur Combiflex 930/933 system
- High-performance flexible waterproof joint protection
- Long-term resistance to water ingress and structural movement
- Full compliance with potable water regulations and DWI requirements
This project demonstrates TSM’s expertise in specialist waterproofing and clean water infrastructure maintenance within highly regulated environments. Through meticulous preparation, technical precision, and strict regulatory compliance, TSM delivered a robust waterproofing solution designed to protect critical water infrastructure assets for the long term.
For more information on TSM’s specialist waterproofing and water industry services, visit Total Specialist Maintenance (TSM)