Building standard 3.3 - flooding and groundwater guidance review: research

1. Introduction

Project background

1.1 The planning process in Scotland offers one of the key controls on flood risk to new development. National Planning Framework 4 (NPF4) promotes the avoidance of new development in flood risk areas from all sources of flooding. Under NPF4 Policy 22, exceptions are only possible under strict criteria (such as re-use of buildings of the same vulnerability class). Flood risk can be identified using SEPA's Flood Maps often followed by more detailed site specific Flood Risk Assessments undertaken by specialists. The planning authority consults SEPA and the local authority's flood team (or equivalent) on flooding matters before making a recommendation for a planning decision. While the key principle of flood risk management in the planning process is one of avoidance of the risk (e.g. by locating the development within the site boundary at a higher elevation than the flood level), occasionally planning conditions relating to flooding may be attached to a planning consent. These could include setting a finished floor level to a particular level above the estimated flood level or the use of some form of Property Flood Resilience (PFR).

1.2 PFR are measures which can be implemented at a property level to significantly reduce the impact of flooding to a property. PFR measures are often broken down into 'resistance' and 'recoverability':

1.2.1 Resistance measures aim to keep floodwater outside the property. This includes measures such as door guards, airbrick covers, non-return valves and sump/pumps.

1.2.2 Recoverability measures limit the damage caused as a result of water entering a property. This includes measures such as waterproof plaster, raised electric sockets and solid concrete floors. These measures aim to reduce flood damage and shorten the recovery period after a flood.

1.3 Once planning permission for a development is obtained, a building warrant is required for construction. A local authority's building standards team (which is separate from its planning and flood teams) is responsible for granting permission for building work to be undertaken (building warrant) and for a completed building to be occupied (completion certificate). This process includes site checks for verification of compliance with the relevant building standards. With respect to flood risk, this could include checking that the building location and finished floor level is per the agreed plans or that other flood protection measures such as PFR have been implemented as agreed or conditioned as part of the planning permission. PFR could feature at the initial building warrant application stage and then be checked for compliance as part of the completion certificate. However, it is not known how frequently compliance checks in relation to flooding matters are undertaken.

1.4 Building Standard 3.3 "Flooding and groundwater" requires that “every building must be designed and constructed in such a way that there will not be a threat to the building or the health of the occupants as a result of flooding and the accumulation of ground water”. Section 3, Environment of the Technical Handbooks provides guidance in support of Standard 3.3, which, if followed in full, is accepted by a local authority verifier as demonstrating compliance with the standard. This includes undertaking a groundwater impact assessment, flood risk assessment and appropriate consideration of flood resistant and resilient construction in flood risk areas. While these assessments should usually have been undertaken at the planning stage, it is the role of both local authority building standards and planning departments to ensure that building developments are ‘suitable for use’ in relation to flooding.

1.5 If a proposed development meets the exception criteria for planning permission to develop in a flood risk area (e.g. re-development of an existing building within the same vulnerability class), then an option for helping to reduce the flood risk is PFR.

1.6 The Building Standards Division (BSD) of the Scottish Government, as part of the Property Flood Resilience Delivery Group, identified via a survey that:

• Section 3.3. of the Technical Handbook guidance needs to better explain the role of building standards in managing flood risk and how building regulations address flooding and flood risk separately from the planning application process.
• the Technical Handbook guidance needs to be strengthened and updated to take account of recently published guidance, for example in the CIRIA Code of Practice and BS 85500.
• more detailed guidance is needed on how PFR can be incorporated into the design of dwellings and buildings.
• where existing buildings have been flooded there is support for guidance on ‘building back better’. More education is needed to explain the benefits of ‘build back better’ and PFR.

1.7 This project was therefore commissioned by BSD to inform the review of guidance published in support of Building Standard 3.3 ‘Flooding and Groundwater’.

Aims and approach

1.8 The main aims of the work were:

• To identify and develop good practice that can be used by verifiers when assessing building warrant applications against building standard 3.3 - Flooding and groundwater, including improving the cohesion of flood risk assessment and mitigation across the planning and building warrant application processes.
• To identify the current guidance and practices used by the flood industry when designing dwellings and buildings to mitigate flood risk by incorporating flood resistance and recoverability techniques and products into building design.

1.9 The following specific activities were undertaken for this study:

• Inception meeting with BSD.
• Consultation of local authorities and other relevant industry contacts via a survey.
• Literature review.
• Analysis of the information assembled.
• Proposal for a good practice template for the processing of applications for development in flood risk areas.
• Further consultation with local authorities on the above.
• Reporting.