Ratcliffe Place, Keswick,
The Brief
RIDA Reports was appointed to undertake a detailed flood risk assessment for a proposed residential development at 9 Ratcliffe Place, Keswick, CA12 4DZ. The project involves the change of use and conversion of an existing garage into an additional habitable living space.
Why the Client Chose RIDA
The client required expert flood risk guidance to support their planning application for a change of use within a known flood zone. RIDA was chosen to deliver a robust assessment to ensure the development would meet the stringent requirements of the National Planning Policy Framework (NPPF) and local planning policies, whilst keeping the new living space safe for its lifetime.
The Challenge
The site is located in Environment Agency Flood Zone 2, indicating a medium probability of fluvial flooding from the nearby River Greta. Additionally, the assessment identified a high risk of groundwater flooding for the property. A significant site-specific constraint was that raising the finished floor level to the recommended 300mm above the design flood level was unachievable due to existing access and structural limitations.
The RIDA Difference
To overcome the floor level constraints and address the fluvial flood risk, RIDA developed a comprehensive ‘water exclusion strategy’. This involved specifying low-permeability building materials, such as engineering bricks, for new wall construction up to 89.15m AOD. RIDA mandated that all new services, electrics, and fittings be elevated above this level, with closed-cell insulation used for pipework and fully sealed service entries.
To directly mitigate the high groundwater flood risk, RIDA recommended the installation of fully sealed concrete floor slabs and the application of a tanking membrane up to 300mm above the external ground level. Furthermore, a Sustainable Drainage Systems (SuDS) approach was outlined to safely manage surface water run-off without increasing off-site flood risk.
The Outcome
The detailed flood risk assessment successfully demonstrated that the garage conversion could be undertaken safely and in full compliance with the NPPF and Environment Agency guidelines. By committing to the specified water exclusion measures, groundwater tanking, and the implementation of a formal Flood Warning and Emergency Response Plan with a clear evacuation route, the development was shown to effectively manage all identified flood risks, providing robust technical evidence to support the planning submission.
