What Makes a Site Sustainable?
A sustainable site is generally one that allows future residents or occupiers to access services, facilities and employment opportunities without excessive reliance on private vehicles.
When assessing sustainability, local authorities will typically consider factors such as proximity to schools, shops, healthcare facilities, public transport, employment areas and other everyday services. The ability to connect to existing infrastructure and integrate with established communities can also be important considerations. Sites adjoining existing towns and villages often perform particularly well because they can make use of existing services and infrastructure while supporting the logical and sustainable growth of settlements. However, sustainability is assessed on a site-by-site basis, and the specific planning context will always be an important factor.
Factors that are often considered include:
What Makes a Site Available?
Availability concerns whether the land can realistically be brought forward for development. Local authorities will typically consider whether there is a willing landowner, whether ownership is clear and whether there are any legal or practical barriers that could prevent development from proceeding. Sites that are actively being promoted and where landowners have expressed an intention to develop or sell are generally viewed more favourably from an availability perspective. Availability does not mean that development will automatically occur, but it does provide confidence that, if a site is considered suitable and achievable, it can be delivered within a realistic timeframe.
Councils typically favour:
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Clear Ownership
Councils generally favour sites where ownership is clear and well understood. Where ownership can be readily established and there are no significant disputes or uncertainties, councils can have greater confidence that the land is genuinely available for development. Clear ownership also helps demonstrate that decisions regarding the future of the site can be made efficiently and that any development proposals have a realistic prospect of being delivered.
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Landowner Intent
Local authorities generally favour sites where the landowner has demonstrated a clear intention to bring the land forward for development. A willing landowner provides greater confidence that a site is genuinely available and capable of being delivered if it is identified as suitable for development. Whether the intention is to develop the site directly, enter into a promotion agreement or sell the land to a developer, a clear commitment to progressing the opportunity is an important consideration in assessing availability.
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No Significant Constraints
Councils generally favour sites that are not subject to major legal obstacles that could prevent development from proceeding. While many legal issues can be resolved, sites with no significant ownership complications, access rights disputes, restrictive covenants or other legal barriers are often considered more readily available for development. The absence of substantial legal constraints can provide greater confidence that a site can be brought forward within a realistic timeframe if it is otherwise suitable and achievable.
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Plan Period Delivery
Local authorities generally favour sites where development can realistically be delivered within the plan period. When assessing availability, councils will consider whether a site is capable of coming forward within the timescales required to meet housing, employment or other development needs. Sites that can be delivered during the lifespan of the Local Plan are often viewed more positively than those that are unlikely to be developed for many years. Demonstrating a realistic delivery strategy, including landowner commitment, access arrangements and an understanding of any key constraints, can help provide confidence that development is achievable within the plan period.
A site may be highly sustainable, but if it is unavailable it is unlikely to be allocated for development through the Local Plan process. Local authorities are not simply looking for sites that are located in the right place; they also need confidence that those sites can realistically be delivered within the plan period. A site may sit adjacent to an existing settlement, benefit from access to schools, shops, employment opportunities and public transport, and perform strongly against many planning policy objectives. However, if there is no willing landowner, ownership is unclear, legal barriers exist or there is no realistic prospect of the land being brought forward, the site may be discounted during the assessment process. Councils are under increasing pressure to demonstrate that sufficient land is available to meet future housing and employment needs, which means deliverability has become a critical consideration. Allocating land that is unlikely to come forward can create significant risks for the planning authority, including delays in meeting development requirements and potential shortfalls in housing supply. For this reason, evidence that a site is genuinely available, supported by a committed landowner and capable of being delivered within a realistic timeframe is often just as important as its sustainability credentials.
What Makes a Site Achievable?
Achievability focuses on whether a site can realistically be developed in practice.
Whilst a site may be sustainable and available, local authorities must also consider whether development is likely to be viable and deliverable within a reasonable timeframe. This involves assessing whether there are any physical, technical, environmental or financial factors that could prevent the site from being successfully developed. Councils will often consider issues such as access arrangements, infrastructure requirements, ground conditions, flood risk, environmental constraints, planning obligations and the overall economics of development. A site that requires extensive mitigation works or significant infrastructure investment may be less achievable than a site with fewer constraints. The key question is whether there is a realistic prospect that development can proceed and be delivered. Sites that are technically feasible, commercially viable and capable of overcoming any identified constraints are generally more likely to be considered achievable and therefore more suitable for allocation or future development.
The question is straightforward:
Can the development realistically be delivered?
Councils will consider:
Market demand
Development costs
Infrastructure requirements
Access arrangements
Site constraints
Commercial viability
Why These Tests Matter
Many Local Plan allocations, HELAA assessments and Call for Sites reviews rely heavily upon the principles of sustainability, availability and achievability. These assessments help local authorities identify which sites are most capable of contributing towards future housing, employment and infrastructure requirements. Whilst every council applies its own methodology, sites that perform well against these core principles are often more likely to progress through the planning process and be considered for allocation. The importance of these tests should not be underestimated. A site may have strong development potential, but if it performs poorly in one of these areas, its prospects can be significantly affected. Equally, sites that demonstrate clear sustainability credentials, genuine availability and a realistic delivery strategy are often viewed more favourably during the assessment process. For landowners, understanding how these principles are applied can provide valuable insight into a site's development prospects. Identifying strengths, addressing weaknesses and presenting robust supporting evidence can all help improve the way a site is viewed by planning authorities when future development opportunities are being considered.
Sites that satisfy all three criteria are generally more likely to progress through the planning system.
How This Affects Land Value
Land capable of satisfying these tests often attract greater interest from:
Developers
Housebuilders
Investors
Land promoters
This is because the planning pathway may be clearer and more achievable.
Frequently Asked Questions
Free Site Assessment
Value My Land can assess whether your land may satisfy the sustainable, available and achievable tests and identify opportunities to improve its prospects for future allocation.