Changes to BNG Coming in August 2026
New statutory regulations affecting biodiversity net gain (BNG) under the Town and Country Planning Act 1990 (TCPA) and the Environment Act 2021 are coming into force on 6th August 2026.
Following DEFRA’s major consultation response aimed at easing administrative burdens and accelerating housing delivery for SME housebuilders, the updates specifically target smaller sites and minor developments.
Background to the BNG Reforms
Based on the standard BNG framework, developers must establish a site’s pre-development baseline biodiversity value at the pre-application stage.
Comparing the baseline against the proposed post-development layout confirms if the scheme results in a net loss or gain, with a formal Biodiversity Gain Plan proving how a minimum 10% net gain will be achieved.
Ecological modelling can be worked into major developments, but feedback from local planning authorities and SME housebuilders has shown that mandatory BNG created disproportionate financial bottlenecks on small plots.
Between high baseline survey costs, complex metric calculations and 30-year site management obligations, small-scale developments inadvertently faced numerous stumbling blocks.
Confirmed Changes Coming 6 August 2026
New 0.2 Hectare Area-Based Exemption
The primary change for housebuilders is a new area-based exemption for developments with a total red-line site boundary of 0.2 hectares or less.
It means that qualifying plots are completely exempt from a mandatory 10% BNG increase, and no statutory metric calculations or biodiversity net gain conditions need to be met.
According to DEFRA, the exemption could cover around 50% of residential planning applications across England.
Instead of just affecting the net developable area, the 0.2 hectare limit applies to the entire red-line boundary, and the exemption doesn’t apply if the site contains pre-existing on-site priority habitats.
Equal Preference for Minor Schemes (>0.2ha)
For non-exempt minor schemes with plots of over 0.2 hectares up to major development thresholds, DEFRA is updating the biodiversity gain hierarchy.
On-site habitat creation and off-site BNG unit delivery now share equal preference.
Housebuilders no longer need to prove that on-site delivery is impossible before resorting to purchasing off-site units, protecting the usable developable space.
That said, applicants still have an obligation under the National Planning Policy Framework (NPPF) to avoid and minimise on-site ecological harm first, and statutory credits remain a strict last resort.
Extended Exemption for Temporary Permissions
The existing exemption for temporary planning permissions has been extended from 2 years up to 5 years, as long as the land can be reinstated to its former condition.
In order to ensure that repeat permissions aren’t abused, cumulative impact monitoring will be used.
Integration of Self-Build and Custom-Build Plots
The standalone exemption for self-build and custom-build schemes is being removed.
Instead, single-dwelling self-build plots are now covered under the broader 0.2 hectare area-based exemption.
Larger Sites and Future Changes
Although changes are confirmed for August, other upcoming policy milestones are coming:
Brownfield Residential Housing (Up to 2.5 Hectares)
DEFRA’s consultation (Considering a Targeted Exemption for Residential Brownfield Development) closed in June 2026.
Government responses outlining definitions, thresholds and final proposals are expected early next year.
Major Infrastructure and Nationally Significant Infrastructure Projects (NSIPs)
Mandatory BNG requirements for NSIPs take effect in November 2026.
Conservation and Municipal Exemptions
Dedicated exemptions for conservation-led habitat restoration projects (e.g. dedicated nature reserves) and developments that enhance municipal public parks, playing fields and gardens will follow later in 2026.
Get Early Advice from Our Team
The 0.2 hectare exemption is designed to save SME developers thousands in compliance overheads as long as your development site qualifies, as assuming you are exempt without verifying your site early can be a costly mistake.
A site boundary slightly over 0.2 hectares or the presence of an unidentified priority habitat can immediately pull your project back into mandatory BNG territory. Trying to resolve BNG at the final hour creates unnecessary planning friction, delays consent, and inflates project costs.
If an ecologist or planning officer discovers a biodiversity net gain requirement right before your submission deadline, scrambling to shoehorn metric calculations or off-site units in at the last minute could create severe delays and unexpected costs.
Refer to Arbtech for Help with Protecting Your Pipeline
As the country’s leading ecology and biodiversity net gain consultancy, we help developers, planners and landowners with navigating regulatory updates with total confidence.
If your site isn’t exempt, we can deliver rapid baseline surveys, clear metric plans and hassle-free off-site unit sourcing. We can also review your red-line boundaries and site baseline early to confirm whether you qualify for the 0.2 hectare exemption for you to submit.
For expert BNG advice and a free quote for the services you need, contact Arbtech via our website, over email or by calling us directly.
