ASH
Biodiversity Net Gain: What Homeowners and Small Builders Need to Know
If you've heard "BNG" mentioned and quietly nodded along, you're not alone. Biodiversity Net Gain means most new development in England must leave nature measurably better off, with a mandatory 10% gain in habitat value. Note: The rules changed this summer, so older advice may be out of date.
1. Small sites may now be exempt
Since 6 August 2026, development on a site of 0.2 hectares or less (the red line boundary on your application—roughly 40m x 50m) is exempt from mandatory BNG, provided it does not affect priority habitat.
2. The standalone self-build exemption has gone
Self-build schemes applying from 6 August no longer have their own dedicated exemption. While small plots may qualify under the 0.2-hectare rule, larger sites or those containing priority habitat now face full BNG compliance.
3. Householders and larger sites
Householder applications (such as minor domestic extensions) remain generally exempt. However, non-exempt sites still require a full assessment, starting with a baseline habitat survey by an ecologist (which can be seasonal).
4. Securing the gain & planning approval
Net gain must be legally secured through on-site habitat, off-site units, or statutory credits as a last resort. A formal Biodiversity Gain Plan usually has to be approved via the discharge of conditions before work can commence, adding fee costs and processing time.
⚠️ Don't Assume You're Exempt
Where your red line is drawn, what habitat exists on site, and the precise type of development all dictate compliance. A miscalculation or wrong assumption can hold up your planning application for months.
Not Sure If BNG Applies to Your Project?
Kippen Ash can tell you early on whether you qualify for an exemption, estimate potential costs if you don't, and advise when to bring in an ecologist.
Email enquiries@kippenash.co.uk