Biodiversity Net Gain requirements
How much BNG is required
A minimum of 10% BNG is required, reflecting the requirements of the Environment Act.
Net gains are additional to any mitigation or compensation that is required to address development impacts.
Development must therefore accord with the mitigation hierarchy and additionally achieve net gains for biodiversity.
What type and scale of development does BNG apply to
BNG does not apply to any development where the on-site habitat includes irreplaceable habitats, as defined in the NPPF Annex 2, nor does it replace existing protections, for example for designated sites or protected species.
The following lists detail the BNG requirements for various types, scales of development and how this should be measured and sets out the national exemptions from BNG.
Major residential development
- Scale
- development is 10 or more dwellings; or
- The number of dwellings is not known and the site area is greater than 0.5 hectares.
- Requirement
- Minimum 10% BNG; on-site opportunities maximised
- Biodiversity Metric
Minor residential development
- Scale
- development of between 1-9 dwellings; or
- the number of dwellings is not known and the site area is less than 0.5 hectares
- Requirement
- (from 2 April 2024) minimum 10% BNG; on-site opportunities maximised
- Biodiversity Metric
- Small Sites Metric (provided no priority habitat or European species are on site)
Major non-residential development
- Scale
- floorspace is 1,000m2 or more; or
- The amount of floorspace is not known and the site area is greater than 1 hectare.
- Requirement
- Minimum 10% BNG; on-site opportunities maximised
- Biodiversity Metric
Minor non-residential development
- Scale
- floorspace is less than 1,000m2; or
- the amount of floorspace is not known and the site area is less than 1 hectare
- Requirement 
- (from 2 April 2024) Minimum 10% BNG; on-site opportunities maximised 
- Biodiversity Metric
- Small Sites Metric (provided no priority habitat or European species are on site)
The requirements for minor development apply to applications made after 2 April 2024.
Type of development exempt from 10% BNG
- householder development
- permitted development
- prior approvals
- development that does not impact priority habitat and impacts less than 25sqm of habitat that has a biodiversity value greater than zero or 5m of linear habitat such as hedgerows
- self-build and custom-build development providing no more than 9 dwellings on a site no larger than 0.5 hectares
- sites developed to provide off-site BNG
Proposals should still include the application of the mitigation hierarchy and appropriate measures that support the enhancement of biodiversity. For example:
- bee bricks
- swifts bricks
- biodiverse landscaping
How is BNG measured
BNG should be measured using the most recent version of the relevant Biodiversity Metric.
The Biodiversity Metric calculates a proxy biodiversity value based on the type and condition of habitats present on site before development and proposed through development. This allows the pre and post-development biodiversity value to be calculated by an ecologist.
View the Statutory Biodiversity Metric and user guide.
At what point in the planning process should BNG be considered
BNG needs to be considered at the very start of the design process with baseline habitat surveys informing the design following the mitigation hierarchy.
Where should BNG be provided
Government guidance confirms that BNG should be achieved in a way that is consistent with the Biodiversity Gain hierarchy. This emphasises that onsite biodiversity gains should be considered first, followed by offsite biodiversity gains on registered sites, with biodiversity credits as a last resort.
BNG should therefore be provided on-site in the first instance and be designed appropriately for the development and local situation.
What if BNG can’t be achieved on-site
Where it's clearly demonstrated that meaningful on-site BNG cannot be achieved, off-site opportunities should be pursued.