Yes. The 10% mandatory BNG requirement doesn't apply to everything. Certain development types are exempt, and understanding where the boundaries lie matters—both for developers who might qualify and for those who assume they do when they don't.
The exemptions exist because applying the full BNG machinery to every minor project would be disproportionate. A householder adding a conservatory doesn't need to commission ecological surveys and register habitat units. But the exemptions are narrower than some developers initially expect, and the consequences of getting it wrong are the same as any other planning breach.
Householder development is exempt. Extensions, outbuildings, and other works within the curtilage of a dwelling house don't trigger BNG. This is the most straightforward category—if you're extending your kitchen, you're not calculating biodiversity units.
Small-scale development below de minimis thresholds is exempt where the development affects less than 25 square metres of habitat, or less than 5 metres of linear habitat like hedgerow. This catches genuinely trivial impacts, but the threshold is lower than many expect. A modest commercial extension can easily exceed 25 square metres of site disturbance.
Permitted development that doesn't require full planning permission is generally outside the BNG regime, since the requirement attaches to planning permissions granted under the Town and Country Planning Act. However, this is more limited than it sounds—many permitted development rights have conditions or prior approval requirements, and some types of permitted development will still interact with ecological constraints through other routes.
Self-build and custom housebuilding has a specific exemption in the regulations. Individual self-builders constructing their own home don't need to deliver 10% net gain. This recognises that applying the full BNG process to one-off self-build plots would be onerous relative to the scale of impact.
Biodiversity gain sites themselves are exempt. Land registered as a habitat bank for generating BNG units doesn't then need to demonstrate BNG when habitat creation works are carried out. This avoids circularity—you can't require net gain on activity that exists solely to provide net gain.
Nationally Significant Infrastructure Projects had a delayed start date. While standard major and minor developments became subject to BNG in February and April 2024 respectively, NSIPs don't face the mandatory requirement until late November 2025. This isn't a permanent exemption—it's a transitional measure recognising that large infrastructure projects have longer lead times and needed more preparation.
The exemptions are narrower than the categories that receive lighter treatment elsewhere in planning.
Brownfield sites are not exempt. There's sometimes an assumption that previously developed land should get a pass, particularly where the existing biodiversity value is low. It doesn't work that way. A site with degraded habitat still has a baseline value under the Defra Metric, and development still needs to deliver 10% above that baseline. The baseline might be low, making the absolute number of units required more modest, but the proportionate obligation is the same.
Developments with low ecological impact are not exempt simply because the impact is small. Unless you fall under a specific exemption category, you're calculating units regardless of whether the site is ecologically interesting. Many development sites have relatively low biodiversity value—arable fields, amenity grassland, hardstanding with scattered vegetation—but low value isn't the same as exempt.
Outline permissions and reserved matters aren't exempt from BNG, though the mechanics work slightly differently. The biodiversity gain condition attaches to the outline permission, and the detailed requirements get resolved through reserved matters and the Biodiversity Gain Plan.
Irreplaceable habitats—ancient woodland, veteran trees, limestone pavements, and certain other habitats that can't be recreated—sit outside the standard BNG framework but aren't "exempt" in the helpful sense. They receive stronger protection, not weaker. Development affecting irreplaceable habitat can't simply offset the impact through biodiversity units; it faces a higher bar of justification and requires bespoke compensation if it proceeds at all.
This catches some applicants off guard. The assumption that ancient woodland might be exempt from BNG is technically correct but practically backwards—it's excluded from the trading system because it's more protected, not less.
The exemption categories are set out in the Biodiversity Gain Requirements (Exemptions) Regulations 2024 and the broader Biodiversity Gain (Town and Country Planning) (Modifications and Amendments) Regulations 2024. Local planning authorities apply these in assessing whether BNG conditions attach to a permission.
If there's genuine doubt about whether a project qualifies for an exemption, it's worth clarifying with the LPA before submission rather than assuming. An applicant who proceeds on the basis of an exemption that doesn't apply will find themselves with a permission they can't lawfully implement—the BNG condition will have attached whether or not they accounted for it.
For developments that don't qualify for exemptions, EcoCapital supplies off-site BNG units through a nationwide habitat bank network, all registered with Natural England. The team can advise early in the process on whether exemptions might apply and, where they don't, what the most cost-effective compliance route looks like.
Units can be reserved pre-planning, and there's a free initial consultation to review the project's ecological position—including whether the BNG requirement applies at all.
