Biodiversity Net Gain Just Got Simpler for Self-Build and Small Extensions in Nottinghamshire and Lincolnshire
If you've been putting off a self-build plot, a small infill scheme, or a modest extension because of Biodiversity Net Gain (BNG) requirements, the rules changed in your favour last month - and it's worth knowing exactly what shifted before you plan your next step.
From 6 August 2026, the government introduced a genuine small-sites exemption from BNG. If your project sits on 0.2 hectares or less and doesn't affect a priority habitat, you may now be able to skip the BNG delivery requirement altogether - no on-site habitat creation, no off-site biodiversity units to buy, no monitoring obligation running for years afterwards.
For clients building or extending across Nottinghamshire and Lincolnshire - where self-build plots and rural infill sites are a real part of the market - this is one of the more practically useful planning changes of 2026.
What actually changed
Before 6 August, every development had to work through the BNG hierarchy: deliver a 10% biodiversity net gain on-site first, then off-site, then as a last resort via a biodiversity credit. Self-build and custom-build housing had its own separate, partial exemption - but it was limited and often left smaller schemes with real cost and paperwork.
The new rules replace that patchwork with one clear small-sites exemption:
Non-major developments of 0.2 hectares or less - provided the site doesn't affect a priority habitat - are exempt from BNG delivery entirely.
The old self-build/custom-build exemption has been withdrawn and folded into this new one. In practice, the government's own guidance notes that most self-build and custom-build projects will fall within the new exemption anyway, simply because of their size.
Major sites - 10 or more dwellings, 0.5 hectares or more, or 1,000 sqm or more of floorspace - still have to follow the full BNG hierarchy. Nothing has changed there.
What this means if you're planning a project
For a typical self-build plot, a garden plot, or a small infill scheme in Nottinghamshire or Lincolnshire, this can mean one less significant cost and process step between you and planning permission - habitat surveys, a BNG metric calculation, and a s.106 monitoring commitment that used to run for 30 years.
A few things worth being clear-eyed about, though:
This is not a blanket exemption from ecology considerations. Protected species legislation, statutory site protections (SSSIs, ancient woodland, and so on), and your local authority's own planning policies still apply in full. A newt survey requirement doesn't disappear because BNG does.
"0.2 hectares" catches most single-plot projects, but check yours. That's roughly half an acre - comfortably covers most individual self-build plots and garden schemes, but a larger rural plot or a small group of new homes could tip over the threshold.
Priority habitat sites are excluded from the exemption regardless of size. If your plot includes species-rich grassland, ancient woodland edge, or similar, the exemption won't apply - this is exactly the kind of thing worth checking with your architect or a local ecologist before you commit to a design.
Why this matters more in Lincolnshire than the headlines suggest
Most national commentary on this change has focused on housebuilders and major sites. But the practical beneficiaries are smaller and more local than that - and Lincolnshire's rural land base, with its self-build plots, agricultural conversions and small infill sites around towns like Grantham, Sleaford and Lincoln, is a good example of exactly the market this exemption was designed for. If you've been quoted for BNG delivery on a small rural plot in the last year, it's worth asking whether that cost still applies.
Getting it right from the start
The exemption removes a cost and a process step - it doesn't remove the need for good planning-led design. A planning-led architect will still check protected species, local ecological policy, and site-specific constraints as a matter of course; the difference now is that a compliant small scheme in Nottinghamshire or Lincolnshire can move through planning without a BNG metric calculation attached to it.
If you're planning a self-build, new build, or extension anywhere across Nottinghamshire, Lincolnshire, Leicestershire or Derbyshire and want to know whether your site qualifies for the new exemption, get in touch for a fee estimate and planning permission check - we'll tell you plainly whether BNG applies to your project before you spend anything on surveys.
FAQs
Does the BNG small-sites exemption apply retrospectively to applications already submitted?
No - this is a forward-looking exemption from the point it took effect (6 August 2026). If you have a live application already working through the BNG hierarchy, speak to your case officer about how the change applies to your specific application.
Does this affect barn conversions?
It depends on the site area and whether priority habitat is present, exactly as with any other small site - a barn conversion on a smaller curtilage may well qualify, but each site needs checking individually.
Do I still need a BNG assessment to find out if I'm exempt?
Not necessarily a full metric calculation, but you (or your architect) still need to establish the site area and check for priority habitat and protected species - that's a much lighter check than a full BNG delivery plan.
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