Archaeology and planning: what a development site may be hiding

Archaeology is not limited to famous ruins or scheduled monuments. A development site can contain buried or standing evidence of past human activity even where nothing appears on the surface, and that evidence can become a material planning issue before an application is determined.

The current August 2026 National Planning Policy Framework deals with archaeology across several heritage policies, particularly HE5 on assessment, HE7 for non-designated heritage assets and HE10 on loss, recording and preservation in situ. Where a proposal has a reasonable potential, based on evidence, to affect a known or undiscovered archaeological heritage asset, the significance of that archaeology and the likely effect of the development need to be understood early enough to inform design, mitigation and the planning decision.

That can mean anything from a desk-based study to geophysical survey or trial trenching before determination. It does not mean that every archaeological find prevents development. The planning response depends on the significance of what may be present, the scale of harm and whether the archaeology can be preserved in situ or appropriately investigated and recorded.

What counts as archaeology in planning?

The NPPF defines archaeological interest by reference to evidence of past human activity worthy of expert investigation. That evidence may survive in buried deposits, earthworks, structures, artefacts, palaeoenvironmental material or the relationship between features across a wider landscape.

An archaeological heritage asset can be designated or non-designated. The distinction matters:

• A scheduled monument is nationally important and has its own statutory protection under the Ancient Monuments and Archaeological Areas Act 1979. Works affecting it may need Scheduled Monument Consent as well as planning permission.
• Most known archaeological sites are not scheduled. They can still be heritage assets and material considerations in a planning application.
• A non-designated archaeological asset that is demonstrably of equivalent significance to a scheduled monument is treated by national policy using the policies for designated heritage assets. That is an important exception to the ordinary non-designated heritage asset balance.

The absence of a scheduled-monument designation therefore does not mean archaeology can be ignored.

Visible earthworks can be part of the archaeological picture too. Our guide to ridge and furrow planning looks specifically at surviving historic field systems, how significance varies and how the August 2026 NPPF applies.

Start with the Historic Environment Record

A Historic Environment Record (HER) is the local information system recording known archaeology and other historic-environment evidence. It may contain records of finds, excavations, cropmarks, historic buildings, former settlements, industrial sites, landscapes and previous investigations.

For a planning proposal with archaeological potential, the HER is normally the starting point. The NPPF expects the relevant HER to be consulted as part of understanding heritage significance. Historic England describes HERs as a primary source for planning, development-control work and land management.

Do not mistake the HER for a definitive map showing every archaeological asset. Absence from the record may simply mean a site has not yet been investigated. Conversely, a HER point may identify evidence without proving that significant remains survive across the whole application site.

The Levelling-up and Regeneration Act 2023 contains a new section 230 duty requiring relevant authorities to maintain Historic Environment Records. As at 20 August 2026, section 230 remains uncommenced. HERs nevertheless already exist across England and remain central to current planning practice; the statutory duty should not be described as operative until it is commenced.

When will an archaeological assessment be required?

An archaeological report should be proportionate to the evidence and the proposal. A council should not demand intrusive investigation merely because archaeology is theoretically possible everywhere, but equally an applicant should not wait until excavation starts where existing evidence points to a realistic archaeological issue.

Triggers can include:

• known archaeological records on or close to the site;
• a site within or near a scheduled monument or other archaeological designation;
• historic maps, aerial photographs, cropmarks or LiDAR suggesting buried features;
• a location within a historic settlement core;
• previous finds or excavations nearby;
• large greenfield development where the archaeological potential has not been tested; or
• a proposal involving substantial ground disturbance in an archaeologically sensitive area.

The local validation list may identify when a desk-based assessment is expected, but the underlying planning question remains whether enough proportionate information is available to understand significance and impact before the decision is made. Our guide to planning validation requirements explains what councils can legitimately ask applicants to provide.

Desk-based assessment

A desk-based assessment (DBA) gathers and analyses existing information about the site’s archaeological and historic environment. It will normally look at the HER, the National Heritage List for England, historic mapping, aerial photography, previous investigations, geology, topography and other relevant documentary sources.

The purpose is not simply to produce a catalogue. A useful DBA should explain:

• what known or potential archaeological assets may be affected;
• their likely significance;
• how reliable the evidence is and where uncertainty remains;
• how the proposed development could affect them; and
• whether further evaluation is needed before the authority can make a sound decision.

For straightforward sites, a proportionate archaeological section within a wider heritage statement may be enough. More complex or higher-risk proposals generally justify a specialist archaeological DBA prepared to current professional standards.

Field evaluation before planning permission

If desk-based evidence cannot establish what survives or how important it is, the authority may need a field evaluation before determining the application. That can include geophysical survey, fieldwalking, test pits or trial trenches depending on the site.

This sometimes frustrates applicants who would prefer archaeology to be dealt with by a condition after permission. But there is a critical distinction: a condition can manage archaeological work where the decision-maker already understands the significance and likely effect well enough to decide the planning merits. It should not be used to postpone investigation that is necessary to establish whether the development is acceptable in principle.

Finding archaeology before determination can also help the developer. It allows important remains to be designed around, avoids discovering a major constraint after land purchase or permission, and makes archaeological costs and programme risks easier to price.

Preservation in situ or preservation by record?

There is no blanket rule requiring every archaeological feature to remain untouched. The appropriate response depends on significance.

For archaeology of high significance, preserving remains in situ may be necessary. That could mean altering building footprints, foundation design, roads, drainage or landscaping so that important remains are retained.

Where loss is justified and the significance does not require preservation in situ, the planning permission may secure archaeological investigation, recording, analysis, archiving and publication. This is sometimes called preservation by record, although the record is not an equal substitute for an irreplaceable archaeological resource and the decision must first justify the loss under the relevant heritage policy.

The current NPPF separates these stages: HE5 deals with understanding archaeological significance before determination, while HE10 deals with preservation in situ where feasible and with investigation, recording, dissemination and archiving where loss is accepted.

Scheduled monuments are a separate consent regime

If the site contains a scheduled monument, planning permission alone is not enough for works caught by section 2 of the Ancient Monuments and Archaeological Areas Act 1979. Scheduled Monument Consent is administered by Historic England on behalf of the Secretary of State.

That regime is particularly important because unauthorised works can be criminal offences and Scheduled Monument Consent cannot simply be obtained retrospectively after the works have happened. Check the scheduled boundary and take specialist advice before ground disturbance.

Areas of Archaeological Importance are different

England also has a separate statutory concept called an Area of Archaeological Importance (AAI) under the Ancient Monuments and Archaeological Areas Act 1979. That is not the same as an ordinary locally defined archaeological priority area or a site merely shown on the HER.

Planning Geek’s AAI glossary page has been checked against the current 1979 Act and the present designated areas. It explains the five English AAIs, the six-week notice procedure and the separate metal-detecting controls.

Archaeology can matter outside a mapped site

Like other heritage issues, archaeology is not always confined to a neat polygon. A proposal may affect the setting of a scheduled monument or another archaeological heritage asset even if no physical remains are disturbed. Landscape relationships, views, topography and historic functional connections can contribute to significance.

There is also a different kind of off-site issue: evidence discovered outside the application boundary can change what is reasonably expected within it. Archaeological potential is an evidence-based judgement, not simply a GIS constraint.

What should an applicant do?

If archaeological potential is identified, a sensible sequence is:

1. Check the HER, National Heritage List for England, local plan/policies map and available archaeological constraint mapping.
2. Speak to the council’s archaeological adviser or county archaeology service early, especially for major or sensitive sites.
3. Commission a proportionate DBA where the evidence justifies it.
4. If necessary, agree the scope of geophysical survey or field evaluation before carrying it out.
5. Use the results to influence layout and design rather than treating archaeology as a report to attach at the end.
6. Where archaeological works will be secured by condition, agree an appropriate Written Scheme of Investigation and make sure the programme allows for fieldwork, analysis, archiving and reporting.

For development affecting several heritage interests, archaeology should sit within the wider assessment of heritage significance and harm rather than being treated as an isolated technical exercise.

Key policy, legislation and guidance

• National Planning Policy Framework, August 2026 – particularly HE5 on assessment, HE7 on non-designated heritage assets and HE10 on loss/removal and archaeological preservation and recording.
• Planning Practice Guidance: Historic environment – significance, HERs, archaeological assessment and decision-making.
• Ancient Monuments and Archaeological Areas Act 1979 – scheduling, Scheduled Monument Consent and Areas of Archaeological Importance.
• Historic England: Historic Environment Records.
• Levelling-up and Regeneration Act 2023, section 230 – provides for a statutory duty on relevant authorities to maintain Historic Environment Records; the commencement position should be checked when relying on the duty in a particular case.

Conservation, Heritage & Protected Sites

Archaeology and Planning Page Updated: 24th August 2026