THE SHORT ANSWER
For small developers, the biggest change this year came on 6 August 2026. Sites of 0.2 hectares or less are now exempt from biodiversity net gain, unless they affect priority habitat on site, and schemes of one to nine homes get a simpler route to buying off-site units. A national Small Sites Aggregator is also being rolled out. The upshot: small sites should be a little less painful to bring forward.
What changed for biodiversity net gain?
Biodiversity net gain, or BNG, requires new development to leave nature at least 10% better off, measured with the government’s metric and secured for 30 years. For a three-house infill site, that has often meant ecologists, metrics and costs out of all proportion to the scheme. From 6 August 2026:
- Sites of 0.2 hectares or less are exempt, measured on the whole red line boundary, unless the development harms priority habitat on site.
- Temporary developments with permission for five years or less are exempt, provided the land is put back afterwards.
- Minor developments (one to nine homes on sites under a hectare) can buy registered off-site units without first having to show they considered delivering the gain on site.
- Self-build and custom-build schemes lose their exemption for applications made on or after 6 August 2026.
The changes apply to applications made on or after that date. Anything submitted earlier follows the old rules.
What is the Small Sites Aggregator?
It’s a Homes England scheme that bundles small brownfield sites together so they’re worth investing in, rather than each being too small to bother with. After pilots in Bristol, Lewisham and Sheffield, housing minister Matthew Pennycook announced a national rollout in May 2026.
The government is also working with 23 councils on a pattern book of standard house designs, due by the end of the year. The aim is to cut design and approval friction on small sites.
What does this mean if you develop small sites?
Less cost and delay on the smallest schemes, and slightly more help finding land. It doesn’t fix the planning system overnight. But if you’ve been put off small infill or brownfield sites by BNG, now is a good time to look again, with a planning consultant who knows your council.
Design matters more than ever on small plots. Every metre of wasted corridor is a metre you can’t rent or sell, which is why the good small-site designers spend so long on the layout before anyone draws an elevation.
This is general information, not planning advice. Check the rules for your site with a planning professional.
Questions people actually ask
Does biodiversity net gain apply to my small site?
For applications made on or after 6 August 2026, sites of 0.2 hectares or less (whole red line boundary) are exempt, unless the development negatively affects priority habitat on site.
What counts as a minor development for BNG?
For housing, one to nine homes on a site under one hectare, or under half a hectare if the number of homes isn’t known.
What is the Small Sites Aggregator?
A Homes England scheme that groups small brownfield sites together to attract investment. It is being rolled out nationally after pilots in Bristol, Lewisham and Sheffield.
