Pol 03 - Flood and Surface water management

Flood Risk Assessment older than five years - KBCN1744

This sentence appears in the definition of 'Flood Risk Assessment': Where more than five years have passed since the FRA was carried out, evidence would be required to demonstrate that the basis of the FRA has not changed in that time. The requirement for evidence that the basis of the FRA has not changed where more than five years have passed is applicable only at Design Stage. It is not required at Post Construction Stage where a compliant FRA was undertaken at Design Stage and the development was carried out in accordance with that design.

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GN38 Relating drainage reports to BREEAM UK NC - KBCN1564

Latest version: v2.0, November 2025 Guidance Note 38 (GN38) has been produced to help assist BREEAM Assessors relate the contents of drainage reports to the ‘Surface water run-off’ and ‘Minimising watercourse pollution’ criteria in Pol 03 for BREEAM UK New Construction 2018, V6/V6.1, and V7. The guidance note does not cover the criteria for ‘Flood resilience’. Completing the template is optional. It is an aid for demonstrating compliance and not a requirement. A separate template exists for BREEAM UK New Construction 2014 (see GN15). Download Guidance Note 38 View all Guidance Notes on BREEAM Projects (licensed assessors only)

27-Nov-2025 - Release of GN38 2.0

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No discharge for up to 5mm rainfall - KBCN0599

The criterion requires no run-off to leave the developed site into the local watercourse(s) for a storm event that results in rainfall depths up to 5mm.  It is not acceptable to collect the rainfall within an attenuation tank and allow the runoff to be released from the site at a restricted rate. This simply slows the rate at which it is released to the watercourse(s). Compliance should be based upon zero runoff from the first 5mm rainfall for 80% of events during summer and 50% in winter.  This is in line with the recommendations within Chapter 24.8 of The SuDs Manual (C753), CIRIA 2015. The 5mm rainfall event is considered one of the most common rainfall events and, therefore, a system should be designed to prevent this run-off leaving the site thus protecting a receiving watercourse from pollution. Where ground conditions prohibit the use of SuDs techniques to manage the rainfall onsite or it is not be possible for the first 5mm of rainfall to be prevented from leaving a site completely.  An appropriately qualified professional must explain comprehensively why this criterion cannot be fully met and design a system to meet the intent of this criterion as far as possible. Where this can be justified and all other relevant criteria have been achieved, the credit can still be awarded.

16.08.2024 Clarification added on calculation requirements and text from KBCN1059 now included.

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