BNG Changes 6 August 2026: Small-Site 0.2ha Exemption and What Surveyors Must Do Now

Last updated: August 24, 2026

Quick Answer: On 6 August 2026, four amendments to England's mandatory Biodiversity Net Gain regime came into force. The most significant is a new small-site exemption: sites of 0.2 hectares or smaller with no onsite priority habitat are no longer subject to mandatory BNG. The 10% net gain requirement itself has not changed. Surveyors and planning consultants must reassess live applications and update their advice immediately.

Key Takeaways

• The 0.2ha small-site exemption removes mandatory BNG for qualifying sites, but only where no onsite priority habitat is present.
• A new temporary development exemption applies where land is fully reinstated within five years or less.
• The self-build and custom-build exemption has been removed for all new applications submitted on or after 6 August 2026.
• Minor development applicants no longer need to demonstrate that onsite delivery was considered before using registered offsite gains.
• The 10% biodiversity net gain threshold remains unchanged.
• DEFRA published transitional arrangements in July 2026 covering how these changes apply to applications already in the system.
• Surveyors must verify site area and priority habitat status before advising any client that a project is exempt.
• Local planning authorities, including Wealden District Council, have begun updating their BNG guidance to reflect the August 2026 amendments.

What Are the Four BNG Changes That Came Into Force on 6 August 2026?

Four targeted amendments to the mandatory BNG framework took effect on 6 August 2026, following secondary legislation laid before Parliament earlier in 2026. These changes do not alter the headline 10% net gain requirement. Instead, they adjust who must comply, under what conditions, and how delivery can be structured for smaller schemes.

The four changes are:

1. New small-site exemption, mandatory BNG does not apply where the development site is 0.2 hectares or smaller and no onsite priority habitat is affected.
2. New temporary development exemption, mandatory BNG does not apply where the land will be fully reinstated to its previous condition within five years or less.
3. Removal of the self-build/custom build exemption, this previously allowed self-build and custom-build homes to sidestep mandatory BNG, but that exemption no longer applies to applications submitted from 6 August 2026 onwards.
4. Flexibility for minor developments, applicants no longer need to demonstrate that onsite delivery was considered before using registered offsite gains. Onsite creation and offsite gains can now be assessed at the same stage, removing a sequencing burden that many practitioners found disproportionate for small schemes.

As noted on the DEFRA environment blog (defraenvironment.blog.gov.uk), these amendments are designed to make the BNG system more proportionate without weakening the overall biodiversity ambition.

What Is the 0.2 Hectare Exemption in the BNG Changes August 2026?

The 0.2ha small-site exemption means that mandatory BNG will not apply to a development site if two conditions are both met: the total site area is 0.2 hectares or smaller, and no onsite priority habitat is present or affected by the development.

This is a significant practical change. Before 6 August 2026, mandatory BNG applied to all major and minor developments in England (with limited existing exemptions). Many small residential conversions, infill plots, and minor commercial developments fell within the regime even where the biodiversity impact was minimal.

Key criteria for the exemption:

• Site area must be 0.2ha or smaller (measured as the total development site, not just the footprint).
• No onsite priority habitat must be present or affected. Priority habitats are those listed under Section 41 of the Natural Environment and Rural Communities Act 2006.
• The exemption applies to applications submitted on or after 6 August 2026. DEFRA's July 2026 transitional arrangements set out how applications already in the system are treated.

Common mistake: Surveyors sometimes measure only the built footprint rather than the full application site boundary. The 0.2ha threshold applies to the entire site as defined in the planning application, not just the area being built on.

For a broader overview of which project types sit outside the mandatory BNG framework, see the full list of exempt projects.

Which Projects Qualify for the 0.2ha BNG Exemption, and Which Do Not?

A project qualifies for the small-site exemption if the application site is 0.2ha or smaller and no Section 41 priority habitat is present onsite. Both conditions must be satisfied simultaneously.

Projects likely to qualify:

• Small infill residential plots in urban areas with no recorded priority habitat.
• Minor commercial extensions on brownfield land under 0.2ha.
• Small-scale permitted development applications where a full application is still required.

Projects that do not qualify:

• Any site over 0.2ha, even marginally.
• Sites under 0.2ha where priority habitat (such as traditional orchard, lowland meadow, or hedgerow) is present or would be affected.
• Self-build and custom-build applications (the separate exemption for these has been removed as of 6 August 2026).

Edge case: A site of exactly 0.2ha falls within the exemption. A site of 0.201ha does not. Accurate site area measurement is therefore critical. Savills has highlighted in its post-August 2026 guidance that boundary discrepancies between OS data and actual application red-line drawings can push sites over the threshold unexpectedly.

How Do the August 2026 BNG Changes Affect Small Sites in Practice?

For sites that qualify under the 0.2ha exemption, mandatory BNG compliance, including the Biodiversity Metric calculation, Biodiversity Gain Plan, and statutory condition, no longer applies. This removes a meaningful cost and time burden for small developers and self-builders working on genuinely low-impact sites.

However, surveyors should note that local planning authorities retain discretion to request ecological information through other policy mechanisms, such as local plan policies or the National Planning Policy Framework. The BNG exemption removes the statutory mandatory requirement; it does not override local planning conditions.

Wealden District Council's updated guidance (published following the August 2026 amendments) advises applicants to confirm exemption status at pre-application stage and to retain documentary evidence that both criteria are met, in case the LPA requests verification.

For clients with sites close to the threshold, a BNG for small development projects assessment may still be commercially valuable even where not strictly required, particularly if the site is near sensitive ecological receptors.

Do Surveyors Still Need a Biodiversity Survey for Sites Under 0.2ha?

The mandatory BNG requirement does not apply to qualifying exempt sites, but a biodiversity survey may still be advisable or required for other reasons. The exemption only removes the mandatory BNG obligation; it does not affect the need for protected species surveys, Habitats Regulations Assessment screening, or locally required ecological appraisals.

When a survey is still needed even for exempt sites:

• Protected species (bats, great crested newts, badgers) are potentially present.
• The LPA's local plan requires an ecological appraisal for all applications.
• The site is adjacent to a designated site (SSSI, LNR, SAC).
• The applicant wants to demonstrate ecological credentials voluntarily.

Understanding what you need for a Biodiversity Net Gain report remains relevant for any site where BNG does apply, even after the August 2026 changes.

What Happens If a Site Is Just Over 0.2 Hectares?

If a site exceeds 0.2ha, mandatory BNG applies in full. There is no sliding scale or partial exemption for sites just above the threshold. A site of 0.21ha carries the same mandatory 10% net gain obligation as a 2ha site.

For sites marginally over 0.2ha, surveyors should consider whether the application boundary can be legitimately redrawn to exclude land not genuinely required for the development. This must reflect the actual development proposal accurately; inflating or artificially shrinking red-line boundaries to achieve exemption status would be inappropriate and could constitute a material misrepresentation.

Where BNG does apply, the metric calculation, biodiversity net gain assessment, and delivery strategy must all be completed before planning permission can be granted.

What Changed for Minor Developments: Onsite vs Offsite BNG Delivery

Before 6 August 2026, minor development applicants had to demonstrate that onsite BNG delivery had been considered and found unsuitable before they could rely on registered offsite gains. This sequential test added cost and delay to small applications.

From 6 August 2026, that sequencing requirement has been removed for minor developments. Applicants can now consider onsite creation and offsite gains simultaneously and at the same stage of the process. This aligns with how larger developments have typically approached the question and removes a disproportionate administrative hurdle.

For surveyors advising on delivery strategy, this means the decision between offsite and onsite BNG delivery can now be made on genuine ecological and commercial merit rather than a prescribed sequence. Offsite options, including BNG off-site land banking and habitat banking, can be evaluated alongside onsite proposals from the outset.

What Are the Transitional Arrangements for Applications Already in the System?

DEFRA published transitional arrangements in July 2026 to clarify how the August 2026 amendments apply to applications submitted before 6 August 2026. The core principle is that applications already validated and under determination are generally assessed under the rules in force at the time of submission.

Key transitional points:

• Applications submitted before 6 August 2026 that were previously exempt as self-build/custom build retain that exemption for the duration of that application.
• Applications submitted on or after 6 August 2026 must be assessed against the new rules, including the removal of the self-build exemption.
• The new 0.2ha small-site exemption and temporary development exemption apply to applications submitted from 6 August 2026 onwards.
• Applicants with live applications close to the 0.2ha threshold should seek advice on whether a revised application submitted after 6 August 2026 would be more advantageous.

Practical Action Checklist for Biodiversity Surveyors After 6 August 2026

Surveyors advising clients on live and prospective applications should work through the following steps:

For every new instruction received from 6 August 2026:

• Confirm the application submission date relative to 6 August 2026 to determine which rules apply.
• Measure the total application site area accurately from the red-line boundary, not just the built footprint.
• Conduct or commission a Phase 1 habitat survey to determine whether any Section 41 priority habitat is present onsite.
• If site is 0.2ha or smaller and no priority habitat is present, confirm exemption status in writing to the client and the LPA at pre-application stage.
• Check whether the client is a self-builder or custom builder. If so, advise that the exemption has been removed for applications from 6 August 2026 and that full BNG compliance is required.
• For temporary developments, confirm the reinstatement timeline. If reinstatement will occur within five years, document this clearly and seek LPA confirmation that the temporary development exemption applies.
• For minor developments where BNG does apply, advise clients that onsite and offsite delivery options can now be assessed simultaneously. Do not default to a sequential approach that is no longer required.
• Review any draft Biodiversity Gain Plans prepared before 6 August 2026 to ensure they reflect the updated delivery flexibility.
• Keep a record of all exemption decisions with supporting evidence, including site area calculations and habitat survey results.

Is the 0.2ha Exemption the Same Across All UK Regions?

No. Mandatory BNG under the Environment Act 2021 applies only in England. Wales, Scotland, and Northern Ireland have separate legislative frameworks and do not operate under the same mandatory BNG regime. The 6 August 2026 amendments, including the 0.2ha small-site exemption, apply exclusively to planning applications in England.

Within England, all local planning authorities are bound by the national mandatory BNG framework. However, individual LPAs may have additional local plan policies that require ecological mitigation or enhancement beyond the mandatory BNG floor. Surveyors operating in areas with strong local ecology policies, such as those covering the South Downs National Park or areas with high concentrations of priority habitats, should check local plan requirements even for exempt sites.

Frequently Asked Questions

Q: Does the 0.2ha exemption mean no ecological work is needed at all?
A: No. The exemption removes the mandatory BNG obligation, but protected species surveys, local plan ecology policies, and other statutory requirements still apply. Always check for protected species and local policy requirements before advising a client that no ecological work is needed.

Q: Has the 10% biodiversity net gain requirement changed?
A: No. The 10% net gain requirement remains unchanged. The August 2026 amendments adjust who must comply and how delivery can be structured, not the level of gain required.

Q: My client submitted a self-build application before 6 August 2026. Does the removal of the self-build exemption affect them?
A: No, for that specific application. DEFRA's July 2026 transitional arrangements confirm that applications submitted before 6 August 2026 are assessed under the rules in force at submission. The removal of the self-build exemption applies only to new applications submitted from 6 August 2026 onwards.

Q: Can a temporary construction compound qualify for the temporary development exemption?
A: Potentially, yes, if the land will be fully reinstated to its previous condition within five years. The key test is full reinstatement within the five-year window. Partial reinstatement or change of use after the temporary period would not qualify.

Q: Do I still need to submit a Biodiversity Metric calculation for an exempt site?
A: For sites qualifying under the 0.2ha or temporary development exemption, a statutory Biodiversity Metric calculation and Biodiversity Gain Plan are not required as part of mandatory BNG compliance. However, some LPAs may still request ecological information through local plan conditions.

Q: How does the new offsite delivery flexibility work for minor developments?
A: From 6 August 2026, minor development applicants no longer need to demonstrate that onsite delivery was considered and rejected before accessing registered offsite gains. Onsite and offsite options can be evaluated at the same time, giving applicants and their surveyors more flexibility to choose the most ecologically and commercially appropriate delivery route.

Conclusion

The BNG changes of 6 August 2026 represent a meaningful recalibration of England's mandatory biodiversity net gain framework, not a weakening of it. The 10% net gain target stands firm. What has changed is proportionality: small sites under 0.2ha with no priority habitat, genuinely temporary developments, and minor schemes seeking offsite delivery all benefit from reduced administrative burden.

For biodiversity surveyors and planning consultants, the immediate priorities are clear. Verify site area and priority habitat status on every new instruction. Update advice for self-build clients who can no longer rely on the exemption. Reassess delivery strategies for minor developments now that the onsite-first sequencing requirement has been removed. And document exemption decisions carefully, because LPAs will expect to see the evidence.

Practitioners who build these checks into their standard workflow from today will be well placed to advise clients accurately and avoid the costly errors that come from applying outdated rules to new applications.

.bng-tool{font-family:Arial,sans-serif;max-width:480px;margin:2rem auto;padding:1.5rem;border:2px solid #2e7d32;border-radius:8px;background:#f9fbe7}
.bng-tool h2{margin:0 0 1rem;font-size:1.1rem;color:#1b5e20}
.bng-tool label{display:block;margin:.7rem 0 .2rem;font-size:.9rem;color:#333}
.bng-tool input[type=number],.bng-tool select{width:100%;padding:.5rem;border:1px solid #aaa;border-radius:4px;font-size:.9rem;box-sizing:border-box}
.bng-tool button{margin-top:1rem;width:100%;padding:.7rem;background:#2e7d32;color:#fff;border:none;border-radius:4px;font-size:1rem;cursor:pointer}
.bng-tool button:hover{background:#1b5e20}
#bng-result{margin-top:1rem;padding:.8rem;border-radius:4px;font-size:.9rem;display:none}
.bng-exempt{background:#c8e6c9;color:#1b5e20;border:1px solid #81c784}
.bng-required{background:#ffcdd2;color:#b71c1c;border:1px solid #e57373}
.bng-note{font-size:.78rem;color:#555;margin-top:.5rem}

function checkBNG(){
var area=parseFloat(document.getElementById(“siteArea”).value);
var ph=document.getElementById(“priorityHabitat”).value;
var td=document.getElementById(“tempDev”).value;
var r=document.getElementById(“bng-result”);
r.style.display=”block”;
if(isNaN(area)||!ph||!td){r.className=”bng-required”;r.innerHTML=”Please complete all fields.”;return;}
if(td===”yes”){r.className=”bng-exempt”;r.innerHTML=”Likely Exempt (Temporary Development): Mandatory BNG may not apply if full reinstatement occurs within 5 years. Confirm with your LPA and document the reinstatement commitment.

“;return;}
if(area<=0.2&&ph==="no"){r.className="bng-exempt";r.innerHTML="Likely Exempt (0.2ha Small-Site): Site is 0.2ha or smaller with no priority habitat. Mandatory BNG does not apply from 6 Aug 2026. Confirm in writing with the LPA.

“;return;}
if(ph===”unknown”){r.className=”bng-required”;r.innerHTML=”Survey Required: Priority habitat status is unknown. A Phase 1 habitat survey is needed before exemption status can be confirmed.”;return;}
r.className=”bng-required”;r.innerHTML=”Mandatory BNG Applies: This site does not qualify for the small-site or temporary development exemption. A 10% net gain must be demonstrated.

“;
}