Residential brownfield exemption
What the Government announced
In the Autumn Budget on 28 October 2026, the Government confirmed that residential developments on brownfield sites of up to 1.5 hectares in England will be exempt from Biodiversity Net Gain (BNG).
The decision follows Defra’s consultation, which ran from 15 April to 10 June 2026 and tested thresholds from 0.5 to 2.5 hectares. The full consultation response, impact assessment, and start date have not yet been published.
The exemption covers residential development only. Commercial, industrial, and other non-residential schemes on brownfield land are not included, nor are Nationally Significant Infrastructure Projects (NSIPs). So, a site under 1.5 hectares is only exempt if it is both brownfield and residential. The consultation proposed that at least 75% of a site must be previously developed on land to qualify, but the final definition, including how mixed-use schemes are treated, is still to be confirmed.
What it means for developers
This is the second BNG exemption this year. Since 6 August 2026, sites of 0.2 hectares or less have been exempt, subject to protections for priority habitats.
Contrary to some beliefs, brownfield land is not automatically low in nature value. CIEEM, the professional body for ecologists, notes that brownfield sites often support incredibly important habitats and species, particularly in urban areas. The Government has not yet published the impact assessment showing how the exemption affects housing delivery or nature.
BNG also continues to grow elsewhere, becoming mandatory for NSIPs from November 2026. Industry bodies, including the BNG Federation, have said they will seek the Government’s evidence and potentially consider a challenge. We will follow these developments with interest.
For now, nothing has changed. BNG still applies to residential brownfield sites above 0.2 hectares, and to all non-residential development in scope, until the new exemption is legislated and in force. Developers with questions about their obligations can talk to our team about Biodiversity Units.