BNG Exemptions: What Developments Are Exempt from BNG?
From existing exemptions to Biodiversity Net Gain requirements for small sites to the Government’s newly announced plans for brownfield housing, here is what developers need to know about the rules and the changes ahead.
Most developments in England are currently legally required to deliver at least a 10% increase in biodiversity, measured using the statutory biodiversity metric.
There are, however, some exemptions for developments, including smaller projects, where applying the full requirements may be disproportionate.
It is important to understand early on in the planning process if the development qualifies for an exemption. This will help developers understand their obligations, plan their budgets and avoid any unnecessary delays.
Which developments are currently exempt from BNG?
Several types of development are currently exempt from mandatory BNG requirements in England.
1. Small developments
Any planning applications made on or after 6 August 2026 for developments on sites of 0.2 hectares or less may qualify for an exemption. This is provided they do not affect on-site priority habitats.
It is important that developers check the relevant eligibility conditions before assuming their project qualifies.
2. ‘De minimis’ developments
Some developments have such a small impact on existing habitats that they fall under the de minimis exemption.
To qualify, a development must not affect any on-site priority habitat and must impact less than:
- 25 square metres of on-site habitat.
- Five metres of linear habitat, such as a hedgerow.
3. Householder applications
Householder developments are exempt from mandatory BNG. These include certain applications relating to existing homes, such as extensions.
4. Temporary development
Certain temporary developments are exempt where the planning permission is limited to five years or less.
The development must consist entirely of temporary development, must not affect on-site priority habitats and must include the required conditions for removing the development and reinstating the land.
This applies to qualifying planning applications made on or after 6 August 2026.
5. Other specific exemptions
Certain other types of development are also exempt, including urgent Crown development, development undertaken to create a biodiversity gain site and development related to the high-speed railway transport network, such as HS2. Note that the previous exemption for small-scale self-build and custom housebuilding was removed for applications made on or after 6 August 2026; these projects now need to rely on the 0.2 hectare exemption instead.
The full BNG exemptions are listed on the government website. Developers should check the current guidance before relying on an exemption.
New proposed BNG exemption for brownfield sites
The Autumn Budget 2026 announced plans for a new exemption for residential developments on brownfield sites of up to 1.5 hectares in England. This is intended to make housebuilding cheaper and simpler and supports the Government’s ambition to prioritise brownfield sites for new homes. However, the consultation also proposed at least 75% of the site must be previously developed land, with safeguards for priority habitats.
For developers working on smaller brownfield sites, this could mean they will no longer need to calculate their biodiversity baseline, plan habitat enhancements and potentially purchase off-site BNG units.
The Government’s response to its consultation on the exemption will reveal the full details and start date. Until it comes into force, brownfield schemes remain subject to the current BNG rules. Developers should check the latest government guidance before assuming their project is exempt.
Why does this matter for biodiversity?
Contrary to popular belief, brownfield sites can often be home to a variety of habitats and wildlife, such as wildflowers, insects and birds. Some support open mosaic habitat, which is a priority habitat in its own right.
With the proposed exemption, developers must consider how biodiversity will be addressed in the planning process where mandatory BNG no longer applies.
Developers should still consider protecting existing habitats and the environmental impacts of a development even if it may be exempt from BNG requirements.
How can developers check whether they qualify for an exemption?
Before progressing with a planning application, developers should:
- Identify the type of development and check whether it falls within an existing exemption or the proposed brownfield exemption, once it is in force.
- Check the site area and habitats – size alone will not establish eligibility, as exemptions do not apply where on-site priority habitat is affected.
- Confirm the relevant application date – some exemptions apply only to applications made on or after specific dates.
- Consult the latest government guidance on eligibility for exemptions.
- Seek ecological advice where needed from a qualified ecologist.
How will BNG requirements evolve in the future?
While smaller brownfield residential developments are set to be exempt from BNG requirements, mandatory BNG is being extended to Nationally Significant Infrastructure Projects (NSIPs) from 2 November 2026. This highlights the Government’s continued development of BNG policy across different types of development.
For this reason, it is important that developers stay informed about policy changes. An exemption that applies to one project may not apply to another, even where the developments appear similar.
At BNG Units Ltd, we recognise that understanding BNG requirements early can help developers make informed decisions about their projects. Where BNG is mandatory, off-site units can offer a simple way to meet those requirements while supporting long-term habitat creation and management.
Planning a development in East Anglia? Contact BNG Units Ltd to understand your options.