Biodiversity Net Gain (BNG) is often associated with large or greenfield development, but the statutory requirement also affects many minor and smaller schemes. For commercial operators and developers, understanding how BNG applies to minor development, and where exemptions exist, is important in managing scope, cost and programme.

While the scale of development may be modest, the legal framework is the same, and assumptions that BNG can be ignored for smaller sites frequently lead to delay.

What is meant by minor development?

For BNG purposes, minor development is generally defined as development that:

  • involves no more than one dwelling, or
  • where the number of dwellings is between two and nine on a site of less than one hectare, or
  • non-residential development creating less than 1,000 square metres of floorspace, or
  • development on a site of less than one hectare where the floorspace created is below this threshold.

Many commercial schemes, including small redevelopments, extensions, changes of use and reconfigurations, fall within this category.

Does BNG apply to minor development?

Yes, in most cases. The BNG requirement applies to minor development unless a specific statutory exemption or transitional provision applies. The fact that a site is small, constrained or previously developed does not automatically remove the requirement.

For minor schemes, the process may be simpler, but the obligation to demonstrate biodiversity gain remains.

How BNG is applied to minor sites

For smaller developments, biodiversity assessment is usually proportionate to the scale of impact. This often involves:

  • establishing a baseline using the small sites version of the biodiversity metric
  • identifying any existing habitats affected by the proposal
  • demonstrating how a minimum 10% net gain will be achieved

On many minor commercial sites, existing biodiversity value may be low. However, even limited baseline value must be accounted for, and loss of habitats such as grassland, scrub or boundary features can still trigger the need for compensation.

On-site delivery for minor development

On constrained sites, on-site biodiversity enhancements may be limited but can still contribute meaningfully. Typical measures include:

  • enhanced landscaping schemes
  • planting of native species
  • green roofs or walls
  • improved boundary treatments

For some minor developments, on-site provision alone may be sufficient to achieve the required net gain, particularly where baseline value is low.

Off-site delivery and credits

Where on-site provision is not sufficient or practical, minor developments can rely on off-site biodiversity units or, as a last resort, statutory biodiversity credits. While this provides flexibility, it introduces additional cost and administrative requirements.

For small schemes, the cost of off-site units can be disproportionate if BNG is identified late in the process, reinforcing the importance of early assessment.

Exception sites and exemptions

There are specific exemptions from BNG which are particularly relevant to smaller developments.

These include:

  • development that does not impact any on-site habitat of biodiversity value, such as works limited entirely to buildings or sealed surfaces
  • certain changes of use where no additional habitat loss occurs
  • householder development (which is excluded entirely)
  • development subject to transitional provisions, where a valid planning application was submitted before the relevant BNG commencement date

In addition, some “de minimis” impacts may fall outside the requirement where biodiversity value is genuinely unaffected. However, these exemptions are narrowly defined and should be relied upon with caution.

Exception sites should not be confused with policy flexibility. Where habitat is affected, even on a small site, BNG is likely to apply unless a clear exemption can be demonstrated.

Securing BNG on minor developments

For minor schemes, BNG is typically secured through planning conditions rather than complex legal agreements. Conditions may require submission of a biodiversity gain plan, confirmation of delivery measures and, where relevant, arrangements for monitoring.

The timing of these conditions is important. Where BNG details are required before commencement, failure to discharge them can delay the start of works, even on relatively small projects.

Practical implications for commercial operators

For commercial and public-facing development, minor works are often expected to proceed quickly. BNG introduces a new consideration that needs to be factored into early feasibility and programme planning.

The key risks arise where BNG is identified late, assumptions are made about exemptions, or the proportionality of information is not agreed with the local planning authority at an early stage.

Summary

Biodiversity Net Gain applies to many minor and smaller developments and should not be overlooked simply because a scheme is modest in scale. While the process for minor sites is intended to be proportionate, the requirement to demonstrate net gain remains unless a specific exemption applies. Early assessment, careful use of exemptions and a clear delivery strategy can help ensure that BNG does not become a barrier to timely implementation.

Disclaimer
This article is provided for general information only and does not constitute planning advice. Planning matters are site-specific and subject to change. Professional advice should be sought before taking action in relation to any particular site or proposal.