If you are planning a new home, small development or building project in Cornwall, recent changes to Biodiversity Net Gain could make a significant difference to your planning application.
From 6 August 2026, the Government introduced changes to Biodiversity Net Gain requirements in England, including a new exemption for development sites of 0.2 hectares or less.
For many smaller projects across Cornwall, this could reduce some of the cost, complexity and ecological work previously associated with securing planning permission.
As architects working across Cornwall from our Newquay studio, we are increasingly seeing Biodiversity Net Gain become an important early consideration when assessing sites for new homes and development.
Here we explain what the 2026 Biodiversity Net Gain changes mean for planning applications in Cornwall and what homeowners, landowners and developers need to know.
What is Biodiversity Net Gain?
Biodiversity Net Gain, usually referred to as BNG, is a planning requirement intended to ensure that development leaves biodiversity in a measurably better condition than it was before.
Where mandatory BNG applies, development is generally required to achieve at least a 10% increase in biodiversity value.
Biodiversity value is assessed using the Government’s statutory biodiversity metric, which considers the type, size, condition and strategic significance of habitats.
The required gain can be achieved through habitat creation and enhancement within the development site or, where appropriate, through offsite biodiversity improvements.
What changed to Biodiversity Net Gain in August 2026?
From 6 August 2026, the Government introduced a new area based exemption from mandatory Biodiversity Net Gain.
Under the new rules, BNG does not apply to planning applications where the site within the red line planning application boundary is 0.2 hectares or less, subject to the relevant criteria.
There is an important exception. The exemption does not apply where development negatively affects onsite priority habitat.
For many smaller development sites in Cornwall, this represents a significant change to the planning process.
How big is 0.2 hectares?
0.2 hectares is 2,000 square metres, or approximately half an acre.
Importantly, the measurement relates to the whole site contained within the red line planning application boundary, not simply the footprint of the proposed building.
This distinction could be particularly important for larger gardens, rural properties and development plots.
A proposed dwelling might occupy only a small part of a larger property. However, if the planning application boundary exceeds 0.2 hectares, the new area based exemption would not apply.
What does this mean for development in Cornwall?
The change could be particularly relevant to smaller development projects across Cornwall, including individual new homes, small infill developments, garden plots, replacement dwellings, small parcels of development land, smaller residential developments and certain commercial projects.
Where the total planning application site is no greater than 0.2 hectares and no priority habitat is negatively affected, mandatory BNG may no longer apply.
For suitable projects, this could reduce some of the ecological assessment, design work and potential costs associated with achieving a calculated 10% biodiversity gain.
However, being exempt from BNG does not mean that planning permission will automatically be granted. Planning policy, design, landscape, access, neighbouring properties, heritage, drainage and ecology may all still influence whether development is acceptable.
What do the changes mean for self build homes in Cornwall?
There is another important change for anyone considering building their own home.
The previous self build and custom build BNG exemption has been removed for new planning applications made from 6 August 2026.
However, this does not mean every new self build home will require 10% Biodiversity Net Gain.
A self build proposal on a site of 0.2 hectares or less may instead qualify for the new area based exemption, provided the relevant requirements are met.
For larger self build sites, BNG may now become a more important consideration during the planning and design process.
If you are considering buying a plot to build a house in Cornwall, understanding this before purchasing the land could help identify potential requirements and costs at an early stage.
Do I still need an ecologist if my development is exempt from BNG?
Potentially.
An exemption from mandatory Biodiversity Net Gain does not mean an exemption from ecology.
Depending on the site and proposed development, ecological considerations could include bats, nesting birds, reptiles and other protected species, as well as trees, hedgerows, Cornish hedges, priority habitats, habitat connectivity and nearby designated ecological sites.
Ecological surveys and mitigation may therefore still be required to support a planning application, even where mandatory BNG does not apply.
Cornish hedges, trees and existing habitats
Cornwall’s landscape has particular characteristics which need to be understood when developing land.
Traditional Cornish hedges, established trees, field boundaries and existing vegetation can make an important contribution to biodiversity as well as the landscape character of a site.
Rather than seeing these features simply as constraints, good architectural and landscape design can often incorporate them into a development.
Understanding ecology at the beginning of a project can influence where buildings are positioned, how access is created and how a development responds to its surroundings.
Where BNG does apply, early collaboration between the architect, ecologist and landscape designer can also help ensure that biodiversity requirements are incorporated into the design rather than addressed once the layout has already been developed.
Buying or developing land in Cornwall
The BNG changes highlight the importance of understanding the opportunities and constraints of a site before purchasing land or investing heavily in a design.
If you are considering buying land for development in Cornwall, an early architectural feasibility study can help establish whether the principle of development is likely to be acceptable, what scale of development the site might accommodate and which planning policies are relevant. It can also identify potential access and highways considerations, landscape and heritage constraints, ecological requirements, whether mandatory BNG is likely to apply and which specialist consultants may be required.
A site may initially appear suitable for development but have planning, ecological, landscape or access constraints which significantly influence what can actually be achieved.
Understanding these issues early can help reduce risk and provide a clearer route towards a planning application.
Planning permission and Biodiversity Net Gain in Cornwall
Cornwall Council has confirmed that the new BNG exemption applies to new planning applications received from 6 August 2026.
For homeowners, landowners and developers, the change could remove mandatory BNG requirements from a significant number of smaller development proposals across Cornwall.
However, every site is different.
Whether land is suitable for development depends on the relationship between planning policy, architecture, landscape, ecology, access and the particular characteristics of the site.
The strongest projects identify these matters early and allow them to inform the design.
Thinking about building or developing land in Cornwall?
Co Create Architects is a RIBA Chartered architecture practice working with homeowners, landowners and developers throughout Cornwall.
From our Newquay studio, we work on projects across Newquay, North Cornwall and the wider county, ranging from extensions and individual new homes to residential developments, conversions and larger development opportunities.
Our team can help with early feasibility work, architectural design, planning applications and the coordination of the specialist consultants needed to progress a project.
If you are considering building in Cornwall, applying for planning permission or assessing land for development, get in touch with Co Create Architects to discuss your site and what might be possible.
This article provides general information on Biodiversity Net Gain and the changes introduced from 6 August 2026. Requirements will depend on the individual development, site characteristics and applicable planning and ecological requirements.right way forward.
Thinking about a project in Cornwall?
Speak to our Newquay team about your site, property or development ideas and find out how Co Create Architects can help you take the first steps.
