BNG is a statutory pre-commencement condition. For NHS organisations delivering new hospitals, diagnostic hubs and community health infrastructure, the sequencing of compliance matters as much as the substance.

Introduction

Biodiversity Net Gain ("BNG") is not a planning consideration to be addressed at the end of a capital project. We have previously explored what BNG is, and in summary it is a statutory pre-commencement condition: development cannot lawfully begin until a biodiversity gain plan has been submitted to and approved by the local planning authority. For NHS organisations running complex capital programmes – new hospitals, campus redevelopments, community health infrastructure delivered in phases over several years – getting the sequencing wrong carries real programme risk.

Once planning permission has been granted, a Biodiversity Gain Plan must be submitted and approved by the planning authority before commencement of the development. That statement is straightforward for a simple single-phase project. 

For major NHS capital schemes, where outline permissions are common, where phasing is the norm, and where reserved matters may be determined years after the original grant, the statutory framework is considerably more demanding. This article sets out what NHS capital project teams and their advisers need to know.

The baseline obligation: what must happen before works start

Subject to some exceptions, every grant of planning permission is deemed to have been granted subject to the condition that the biodiversity gain objective is met – that is, for development to deliver at least a 10% increase in biodiversity value relative to the pre-development biodiversity value of the onsite habitat. This increase can be achieved through:

• Onsite biodiversity gains, 
• Registered offsite biodiversity gains, or 
• Statutory biodiversity credits. 

BNG commenced for planning permissions granted in respect of an application made on or after 12 February 2024. Permissions granted for applications made before this date are not subject to biodiversity net gain.

Where BNG does apply, when a planning application is submitted for development which the applicant believes is subject to the biodiversity gain condition, there are minimum national information requirements related to biodiversity net gain which the applicant must provide. These requirements will allow consideration of existing habitat baselines so there is a common understanding about the pre-development biodiversity value of the development's onsite habitat at this stage. 

This means ecological survey work is not something that can be deferred to post-permission. Surveys of the development site to calculate the pre-development biodiversity value of the onsite habitat should ideally be done shortly before the submission of the planning application to ensure the pre-development biodiversity value is accurate. If there has been a material change since a survey, it should not be used.

For NHS projects with long pre-application periods – common in major hospital schemes – this has direct implications for when ecological surveys must be commissioned.

Phased development: A different and more demanding regime

Major NHS capital projects are typically delivered in phases. A new hospital may be built over several years, with enabling works, construction, fit-out and commissioning each representing a distinct phase. An NHS estate redevelopment may involve the progressive decant of services, demolition of existing buildings and construction of new facilities across a decade or more. The statutory framework for biodiversity net gain includes specific modifications for planning permissions that have the effect of permitting development which proceeds in phases, reflecting that phased development can occur over a long period of time where full details of all phases may not be known at the time of planning permission. 

These modifications apply to: a grant of outline planning permission where the reservation of matters for subsequent approval has the effect of requiring or permitting development to proceed in phases; or a grant of any kind of planning permission, where the grant is subject to conditions which require development to proceed in phases. Not every outline permission will engage the phased regime – an outline permission for a small-scale development where appearance and landscaping were the only reserved matters is unlikely to do so – but most substantial NHS capital projects will.

Where the phased regime applies, the standard single biodiversity gain plan requirement is replaced by a two-plan structure:

• An Overall Biodiversity Gain Plan must be submitted to and approved by the planning authority before any development can begin; and
• A Phase Biodiversity Gain Plan for each phase must be submitted to and approved by the planning authority before the development of that phase can begin. 

This creates a layered, sequential obligation that runs throughout the life of the project.

The Overall Biodiversity Gain Plan: What it must contain and when it is needed

The content of an Overall Biodiversity Gain Plan is different in several ways from a standard Biodiversity Gain Plan, reflecting that there is unlikely to be detailed proposals agreed at the outset. 

The purpose of the Overall Biodiversity Gain Plan is to confirm that there is a clear upfront framework for how the biodiversity gain objective of at least 10% gain is expected to be met across the entire development. Each Phase Biodiversity Gain Plan will subsequently set out a phase's contribution to biodiversity net gain and confirm progress towards the overall biodiversity gain objective once clear proposals for each phase have been developed. 

The Overall Plan must include information about the steps taken or to be taken to minimise adverse effects on the biodiversity of the onsite habitat; the pre-development biodiversity value of the entire onsite habitat; any registered offsite biodiversity gain allocated or proposed to be allocated to the entire development; any biodiversity credits purchased or proposed to be purchased; and the post-development biodiversity value of the onsite habitat for the entire development and for each phase of development. 

Importantly, where firm proposals for development and habitat enhancement on each phase have yet to be finalised, assumptions about the likely development and habitat enhancements should be used to determine the post-development value for each phase. This value will set the expectations about the biodiversity value of onsite habitats, and the final value will need to be set out in later Phase Biodiversity Gain Plans.

For NHS project teams working with evolving designs and long programme timelines, this means the Overall Plan must strike a careful balance: sufficiently detailed to satisfy the planning authority that the 10% objective is achievable, but not so prescriptive that it locks in design assumptions that will change.

The Phase Biodiversity Gain Plan: What it must contain and when it is needed

The Phase Biodiversity Gain Plan is more limited in scope than the Overall Plan. Rather than detailing the overall strategy, it focuses on a phase's contribution to biodiversity net gain and confirms progress towards the overall biodiversity gain objective for the entire development. 

Each Phase Plan must include the post-development biodiversity value of the onsite habitat for the relevant phase; the post-development biodiversity value of the onsite habitat for each other phase (whether begun or not); any registered offsite biodiversity gain allocated to the entire development and the biodiversity value of that gain; any registered offsite gain proposed to be allocated; any biodiversity credits purchased for the entire development; and any biodiversity credits proposed to be purchased. 

Importantly, the biodiversity gain objective of at least 10% net gain applies to the overall development – not to each individual phase. The contribution of each phase may therefore vary, provided that a net gain of at least 10% is achieved for the overall development at the time of its completion. This offers NHS project teams some flexibility in how gain is distributed across phases but also requires careful planning to ensure that early phases do not consume biodiversity value that later phases will struggle to recover.

The planning authority has eight weeks (or another agreed timescale) to determine either Plan, and an appeal can be made if the planning authority has refused or not approved either Plan within that timescale.

Where things can go wrong: Programme risk and design risk

For NHS capital project teams, the following are the principal points of failure:

Late ecological surveys. Applicants are encouraged to consider biodiversity net gain early in the development process and factor it into site selection and design. A pre-development ecological survey commissioned too late – after the planning application has been lodged, or after design has been substantially fixed – risks either inaccurate baseline data or a requirement to re-survey, both of which delay the approval of the biodiversity gain plan and therefore the start of works.

Habitat degradation between survey and commencement. If activities to implement or in connection with a planning permission are carried out after 25 August 2023 that lower the biodiversity value of the onsite habitat, the pre-development biodiversity value of the onsite habitat is taken to be the biodiversity value immediately before the carrying out of those activities. This means that site clearance, enabling works or even routine management activity carried out after survey but before plan approval can affect the calculation – a risk that NHS project teams must actively manage.

Onsite gains not properly secured. Where an applicant relies upon a significant increase in onsite habitat biodiversity value, the habitat enhancement must be subject to a planning condition, section 106 agreement, or conservation covenant requiring the habitat enhancement to be maintained for at least 30 years after the development is completed. For NHS projects, this means that landscaping and habitat schemes intended to contribute to BNG compliance must be properly legally secured.

Section 73 permissions. NHS capital programmes regularly involve variations to planning conditions as designs evolve. If a section 73 permission affects the post-development value of the phased development's onsite habitat or its irreplaceable habitats, a new Overall Plan would be required to be submitted and approved to ensure the biodiversity gain objective will be achieved. Project teams must therefore assess the BNG implications of any section 73 application before it is submitted, as the consequences – a requirement to produce and obtain approval of a new Overall Plan before any further works can commence – can be significant.

Reserved matters and phasing. The approval of reserved matters for outline planning permissions is not itself subject to the biodiversity gain condition. However, it may be appropriate that where an outline planning permission has been granted for a phased development, Phase Biodiversity Gain Plans are prepared alongside the applications for reserved matter approvals for those phases. Aligning the Phase Plan submission with the reserved matters timetable is good practice and avoids the risk of the Phase Plan approval becoming a programme-critical path item at the point of starting works.

Practical recommendations

1. Commission ecological surveys as early as possible – ideally before the planning application is submitted, and certainly before any site clearance or enabling works. Older surveys should only be relied upon if there has been no material change to the onsite habitat.
2. Factor BNG into the masterplan and phasing strategy from the outset. Applicants seeking planning permission for phased development are encouraged to engage with the local planning authority as part of their wider pre-application engagement about the development, so that the strategy for delivering biodiversity net gain is known and factored into the preparation of the development's masterplan and phasing strategy. 
3. Consider submitting a draft Overall Biodiversity Gain Plan with the application. Applicants may want to submit a draft Overall Biodiversity Gain Plan as part of their planning application. Doing so provides early visibility of the BNG strategy, supports pre-application engagement with the LPA, and reduces the risk of the plan becoming a programme bottleneck post-permission.
4. Align Phase Plan submissions with your reserved matters timetable. Do not allow the Phase Biodiversity Gain Plan approval process to sit outside the main programme management framework. It is a condition precedent to the commencement of each phase, and programme teams should treat it accordingly.
5. Assess the BNG implications of any section 73 application. Before varying conditions on a phased permission, take advice on whether the variation affects the post-development biodiversity value of the onsite habitat – if it does, a new Overall Plan will be required.
6. Ensure onsite habitat enhancements are properly legally secured. Landscaping and habitat schemes relied upon for BNG compliance must be secured by a planning condition, section 106 agreement or conservation covenant – not simply described in the application documents.
7. Take specialist legal advice before making commitments. The interaction between BNG obligations, section 106 agreements, conservation covenants, and programme timelines is complex. Early legal engagement materially reduces programme and compliance risk.
8. Consider NHS governance and land-use frameworks. Any BNG commitment on NHS land must be considered alongside NHS property governance requirements, including relevant consents, NHS Property Services arrangements and ICB oversight of major estate decisions

Conclusion

For NHS organisations delivering major capital projects, BNG is not an afterthought or a planning condition to be discharged in the final stages of the planning process. It is a pre-commencement obligation embedded in every relevant planning permission, with a distinct and demanding regime for phased development. Getting it right requires ecological surveys commissioned early, a BNG strategy integrated into the masterplan from the outset, and a programme management approach that treats biodiversity gain plan approvals as the critical-path items they are.

We advise NHS bodies and health-sector clients and have extensive experience advising on all aspects of BNG, including planning obligations, conservation covenants, biodiversity gain plan preparation and programme sequencing. If you would like to discuss how BNG may affect your capital programme, please do not hesitate to get in touch to discuss infrastructure and developments in health.

This article is intended as general information and does not constitute legal advice. Specific advice should be sought in relation to particular circumstances.