BNG reform: a boost for brownfield housing, but what about commercial development?

The Government’s Budget announcement on 28 October proposes removing one of those pressures: mandatory Biodiversity Net Gain (BNG) for residential brownfield developments on sites up to 1.5 hectares in England. However, the proposed exemption does not appear to extend to commercial redevelopment.

 

Defra consulted on a targeted exemption for brownfield residential development between 15 April and 10 June 2026. That consultation has closed, with the Government’s full response still awaited. The Budget now establishes its intention to introduce a 1.5-hectare threshold, but the implementation timetable and detailed eligibility rules remain to be confirmed.

 

For qualifying housing schemes, this will help reduce costs and simplify delivery, particularly where constrained sites offer limited space for habitat creation and developers would otherwise need to purchase offsite biodiversity units.

 

The proposed use matters

The distinction between a site’s previous use and its proposed redevelopment is important.

 

A former industrial or commercial site redeveloped for housing could potentially benefit from the exemption. However, redeveloping that same site for new employment floorspace would fall outside the announced residential exemption. In addition, the treatment of mixed residential and commercial schemes still needs clarification.

 

Commercial schemes may qualify for existing exemptions, including the exemption for sites of 0.2 hectares or below where the relevant conditions are met. Otherwise, the normal requirement to deliver at least 10% BNG continues to apply. Brownfield status alone does not remove that obligation.

 

In our view, this raises a wider question: if the objective is to encourage the reuse of previously developed land, should similar support be available for employment development? Smaller industrial, office and commercial schemes can face many of the same remediation costs, physical constraints and viability pressures as housing.

 

What counts as previously developed land?

Eligibility will also depend on the land itself.

 

The planning definition of previously developed land includes important exclusions, such as land last occupied by agricultural or forestry buildings, residential gardens within built-up areas, and former development whose remains have blended into the landscape. An old building or yard should therefore not automatically be assumed to qualify.

 

The final rules will need to clarify how sites containing both brownfield and undeveloped land are treated, including the proportion that must be previously developed. This makes an early review of planning history, existing features and the application boundary particularly valuable.

 

An opportunity to revisit stalled schemes

For smaller brownfield housing projects, removing mandatory BNG may create an opportunity to revisit proposals previously held back by viability. The potential saving should be considered alongside remediation, infrastructure, affordable housing and other obligations.

 

Emma Hawkes, Associate Director commented:

“The proposed exemption is a welcome step towards making smaller brownfield housing schemes more deliverable. However, commercial redevelopment can face many of the same costs and constraints. Extending proportionate support to employment or mixed use schemes could help bring redundant sites back into use, supporting business growth and jobs alongside new homes.”

However, the announcement should not be treated as an immediate exemption. Until the new rules take effect, applicants should continue to address their existing BNG requirements.

 

For landowners and developers, the opportunity now is to identify sites that could benefit and assess whether the change could improve their prospects of delivery. For commercial projects, early ecological input remains essential to understand the BNG position and build an appropriate strategy into the scheme.