A significant change to England's planning system came into effect on 6 August 2026 which could make many small development sites easier and less expensive to bring forward.
The Government introduced a new exemption from mandatory Biodiversity Net Gain (BNG) for development sites measuring no more than 0.2 hectares — 2,000 square metres.
For landowners and small developers looking at individual plots, infill development and smaller residential sites across the North East, this is an important change. But the exemption is not universal, and several other BNG rules changed at the same time.
BNG explained without the jargon
Biodiversity Net Gain requires qualifying developments to leave biodiversity in a better measurable condition than existed before development. Where mandatory BNG applies, the standard requirement is a minimum 10% net gain in biodiversity.
It is calculated using a statutory biodiversity metric which assesses habitats according to their area, type, distinctiveness, condition and strategic significance. BNG is therefore about considerably more than adding a few trees to a planning drawing, and for some developments it can influence both design and financial viability.
What exactly changed on 6 August 2026?
There are four changes small developers should particularly understand.
1. Sites of 0.2 hectares or less can now be exempt
Development carried out on a site no larger than 0.2 hectares — 2,000m² — is generally exempt from mandatory BNG, subject to important ecological exceptions.
2. The separate self-build exemption has gone
The previous BNG exemption specifically covering qualifying small self-build and custom-build projects has been removed for new applications. Many smaller self-build plots may nevertheless fall within the new 0.2-hectare exemption.
3. Minor developments have more flexibility
Where BNG still applies to a minor development, developers now have greater flexibility to consider registered off-site biodiversity gains alongside creating or improving habitats on the development site.
4. Some temporary developments are exempt
Certain developments which are entirely temporary and where the land will be reinstated within five years or less can also be exempt.
The 2,000m² figure is about the site — not the house
The 0.2-hectare threshold relates to the site included within the red-line planning application boundary.
Imagine two proposals for exactly the same 200m² detached house. One sits on a 1,400m² development site; the other sits on a 3,500m² site. Despite the houses being identical, their potential BNG position could be different because the relevant test concerns the area of the development site.
For developers and landowners, measuring and understanding the site during early feasibility work therefore matters.
Why could this be important in the North East?
The North East contains many development opportunities that do not involve large housing estates: single building plots, garden development, infill and backland sites, former commercial land, redundant buildings, small brownfield sites and individual self-build opportunities.
This is relevant across Newcastle and Gateshead, Sunderland, Middlesbrough and Darlington, as well as smaller towns and rural settlements where individual plots and edge-of-settlement sites are common.
For a qualifying small site, removal of mandatory BNG could potentially avoid elements of habitat assessment specifically required for BNG, metric calculations, Biodiversity Gain Plans, purchasing off-site units and long-term habitat management obligations.
It does not remove every ecological consideration, but it can make the planning process more proportionate to the scale of development.
There is an important priority habitat exception
A site being below 2,000m² does not guarantee exemption. The new exemption cannot generally be used where development would negatively affect priority habitat situated on the site.
A small site containing ecologically valuable habitat can require a very different planning approach from a similar-sized plot comprising hardstanding or low-value managed land. Development land should be assessed on its actual characteristics rather than simply its size.
Ecology has not disappeared from the planning system
It is important not to confuse “BNG exempt” with “no ecological requirements.” They are not the same thing.
Even where mandatory BNG does not apply, development can still be affected by protected species legislation, bats, nesting birds, badgers, trees and hedgerows, ecological designations, Local Wildlife Sites, Sites of Special Scientific Interest, ancient woodland, habitats regulations issues and local planning policy.
A planning authority can still require ecological evidence where it is justified. Our planning application service coordinates the planning strategy and proportionate supporting information for an individual site.
What has changed for self-builders?
Previously, qualifying small-scale self-build and custom-build projects benefited from their own BNG exemption. That standalone exemption has now been removed for new applications from 6 August 2026.
Consider a self-build dwelling on a site measuring 1,750m². The old exemption may have disappeared, but the project could potentially fall within the new 2,000m² area exemption, provided the relevant conditions are satisfied and priority habitat is not adversely affected.
Now consider the same house on a 5,000m² countryside plot. The development cannot rely on the new exemption simply because only one house is proposed. This is particularly relevant to larger plots on the edges of towns and villages.
Our new-build homes service covers feasibility, planning, design and technical coordination for individual and replacement homes.
What if my site is just over 2,000m²?
Crossing the 0.2-hectare threshold does not automatically make development unviable. It simply means this particular exemption is unavailable. Other exemptions could potentially apply depending on the proposal and habitat impacts; otherwise, BNG needs to form part of the development strategy.
If BNG is required, the development will normally need to demonstrate a minimum 10% net gain. This may be delivered through on-site habitat creation, registered off-site biodiversity units or, as a last resort, statutory biodiversity credits.
A more flexible approach for constrained sites
For qualifying minor developments that remain subject to BNG, on-site habitat creation and registered off-site gains can now be considered at the same stage.
This can help constrained urban sites in places such as Newcastle, Gateshead and Sunderland, and compact redevelopment opportunities in Middlesbrough or Darlington, where access, parking, drainage, amenity and a workable layout all compete for limited space.
Temporary development and submission dates
Where the whole development is temporary and the land will be reinstated within five years or less, mandatory BNG may not apply, provided priority habitat is not negatively affected.
The wider changes broadly apply to new planning applications submitted from 6 August 2026 onwards. Earlier applications remain subject to the previous regime and relevant transitional arrangements.
What happens where BNG still applies?
A Biodiversity Gain Plan will normally need to be approved before development can begin. Significant habitat used to secure mandatory BNG may need to be secured and maintained for at least 30 years.
BNG can therefore affect site layout, development capacity, landscape design, legal agreements, consultant costs, long-term land management and overall viability.
Buying land: what should be checked first?
Site area is now an important early question, but it is not the only one. A sound feasibility review should also consider the planning principle, access and highways, neighbouring amenity, trees, ecology, flood risk and drainage, heritage, ground levels, services, design constraints and realistic development capacity.
Those questions vary locally. A brownfield plot in Middlesbrough, an infill opportunity in Darlington, a constrained urban site in Newcastle or Gateshead, and land near Sunderland's coast can each raise different planning and ecological issues.
Our view
For smaller developments, these reforms are a welcome simplification. They should make the planning process more proportionate for straightforward small sites while retaining protection for ecologically important land.
The key is to establish the BNG position before purchasing land or completing a detailed design. A focused feasibility review can clarify whether the exemption is likely to apply, whether ecological advice is needed and whether BNG could affect capacity or viability.
Considering a small development site in the North East?
Hepburn Architects advises homeowners, landowners and small developers across Newcastle, Gateshead, Middlesbrough, Darlington, Sunderland and the wider North East. We support individual new homes, infill and backland development, small residential schemes, conversions and redevelopment opportunities.
If you are considering purchasing or developing a site, contact Hepburn Architects to discuss an early planning and architectural feasibility review.
This article provides general information on the Biodiversity Net Gain rules applying in England from 6 August 2026. Planning and ecological requirements vary according to the circumstances of individual sites and professional advice should be sought where appropriate.
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