NHBC’s Claims team in Northern Ireland is preparing to complete a significant remediation project that highlights the importance of effective, thorough drainage design.
Six properties benefiting from our Buildmark policy’s insurance cover experienced the failure of foul and surface water drainage systems when movement within the surrounding ground led to sections of the underground network becoming displaced and disconnected.
After previous repairs, such as the reconnection of drainage joints, provided only temporary relief for the owners, NHBC’s Claims team got involved to address the underlying cause.
CCTV surveys and comprehensive ground investigations identified widespread settlement across the gardens and paved areas surrounding the properties.
They also revealed poor gradients within the foul drainage network and significant movement within the manhole chambers.
Evidence concluded that the drainage design had not adequately accounted for future ground movement, resulting in deformation, backfalls and disconnection of both foul and surface water drainage runs.
With the extent of the damage meaning a conventional repair would not provide a durable long-term solution, NHBC has developed an engineer-designed remediation scheme involving the installation of piled supports, reinforced concrete ground beams and transition slabs to create a stable platform for a completely reconstructed drainage network.
The new system will be designed to accommodate future movement while maintaining the required falls and functionality.
Mervyn Molyneaux, Claims Area Manager at NHBC, said: “This case is an example of the stress and inconvenience that can be caused by not giving enough consideration to drainage prior to starting construction.
“While the sewers will be repaired for these homeowners under the Buildmark policy, they have nevertheless experienced great distress and disruption.
“I would call on builders in Northern Ireland to consider potential future ground movement when designing drainage systems for challenging ground conditions.”
