80 Moorbridge Road, Maidenhead
The Brief
RIDA Reports was appointed to undertake a detailed flood risk assessment for a proposed development at 80 Moorbridge Road in Maidenhead. The scheme involves the change of use of an existing Class E office building into 27 Class C3 residential apartments.
Why the Client Chose RIDA
The client required specialist flood risk expertise to confidently navigate the planning process for introducing a more vulnerable residential development into a known flood area. They chose RIDA for our proven ability to deliver robust, evidence-based assessments and practical, tailored mitigation strategies that satisfy both local authority and Environment Agency requirements without overcomplicating the build.
The Challenge
The site presented a complex combination of environmental and structural constraints. It is situated within Environment Agency Flood Zone 3, which carries a high probability of fluvial flooding from the nearby Strand Water. Furthermore, the property is at a high risk of groundwater flooding. A significant architectural constraint was that, as a change-of-use project within an existing building, the finished floor level could not be raised to achieve the standard 600mm freeboard clearance above the design flood level, remaining instead at its existing level of 24.6m AOD.
The RIDA Difference
We conducted a detailed flood risk assessment to rigorously evaluate all sources of flooding in accordance with the National Planning Policy Framework (NPPF). To directly address the fluvial risk and the inability to raise the finished floor levels, we developed a comprehensive water exclusion strategy. We specified the use of low-permeability materials—such as engineering bricks and specific mortar mixes—and required that all new sensitive services, electrical fittings, and communications wiring be positioned safely above 25.52m AOD.
To mitigate the high groundwater risk, we recommended a multi-step intervention: incorporating a tanking membrane up to 300mm above ground level, installing fully sealed concrete slabs, and ensuring that clear external flow paths are maintained to safely direct emergent groundwater away from the building. Furthermore, we identified a safe, dry evacuation route directing occupants away from the flood zone via Moorbridge Road and High Street.
The Outcome
The comprehensive assessment successfully demonstrated that the office-to-residential conversion could be made safe for its 50 to 100-year design life without increasing flood risk elsewhere. By detailing a highly specific water exclusion and material resilience strategy, the report provided the essential technical evidence required to fully support the planning application.
