BNG for Small Sites — Explained in 60 Seconds
A quick guide to what LPAs actually need (and what they don’t)
What is BNG?
Biodiversity Net Gain (BNG) is a mandatory requirement for planning applications. For smaller developments, the LPA normally requires a Small Sites Metric (SSM) calculation — a desktop exercise using the DEFRA tool.
When do you need it?
You’ll need an SSM report when:
• the LPA requests BNG before validation
• an ecology statement isn’t required, but BNG still is
• there is a garden, landscaped area, or boundary being altered
• you’re submitting an extension, conversion, outbuilding, or new dwelling(s)
What LPAs expect
- a complete SSM spreadsheet
• a short narrative report summarising baseline + post-development habitat
• a clear plan showing what is being changed
• confirmation that the required BNG uplift is met (or mitigation identified)
What you don’t need
✘ lengthy ecology surveys
✘ site visits
✘ ecological narrative padding
✘ multi-week delays
✘ specialist ecological assessments (SSM is desktop only)
Why outsource SSM?
- saves designer/admin hours
• no risk of LPA bounce-backs
• avoids inflated ecology consultant fees
• keeps the application moving
• easy to pass through to the client
• fast turnaround
How Grove House helps
- SSM calculation completed quickly
• clean, planning-ready BNG report
• sensible, transparent pricing
• “fix and respond” service if the LPA requests clarification
• simple requirements — just send your red-line boundary or site plan
What we need from you
- red-line boundary or site plan
• brief description of the proposal
• LPA name
• any deadlines
Want BNG off your desk?
Email: david@gh-ec.org
Website: https://www.gh-ec.org
Biodiversity Net Gain (BNG) on Small Sites
What is Biodiversity Net Gain (BNG)?
Under the Environment Act 2021, planning permissions in England are subject to a statutory condition requiring at least a +10% Biodiversity Net Gain (BNG) compared to the site baseline. This applies to major sites from February 2024 and will apply to small sites (1–9 dwellings, ≤1 ha) from April 2026.
Local Planning Authorities (LPAs) are already asking for BNG evidence now. Applications without it risk delays or refusals.
When is the Small Sites Metric (SSM) Used?
The DEFRA Small Sites Metric (SSM) is the official government tool for calculating BNG on simple projects, such as:
- Single dwellings
- Residential extensions or conversions
- Small infill developments
It is not suitable if the site contains priority habitats, significant hedgerows, watercourses, or is adjacent to designated ecological sites. In those cases, the full Biodiversity Metric must be used most often requiring involvement of a chartered ecologist.
What’s Involved in an SSM Submission?
To demonstrate compliance, applicants must provide:
- Baseline habitats (e.g. lawns, hardstanding, shrubs, trees, roofs).
- Proposed habitats post-development (e.g. retained grass, new shrubs, green roofs, trees).
- Condition of each habitat (poor/moderate/good).
- Completed SSM Excel workbook (government-issued, macro-enabled).
- Supporting statement summarising enhancements.
The SSM, when correctly applied, calculates:
- Baseline biodiversity units
- Post-development units
- Net change and % uplift
Who Can Complete It?
For small residential schemes, a consultant familiar with the use of the SSM tool can prepare the submission in line with LPA requirements.
Why Use A Specialist?
Removes the burden – we handle the government templates for you.- Planning-ready outputs – accepted by LPAs across England.
- Cost-effective – proportionate service for small sites.
- Faster validation – reduces delays caused by missing BNG evidence.
Our Offer to Planning Consultants & Architects
We provide:
- Site appraisal and analysis
- Completion of the official DEFRA SSM workbook.
- A concise BNG support statement ready for submission.
- Advice on proportionate enhancements (shrubs, trees, green roofs, wildlife features).
You focus on strategy and design – we take care of BNG compliance.
What we offer is – Practical, affordable BNG solutions for small residential projects
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