Archaeological Priority Areas and county archaeologist advice
Archaeology adds months to a programme when it is picked up late. How councils map sensitivity, what the county archaeologist asks for, and how to sequence the work.
If your site falls within an archaeological priority area or an equivalent locally mapped zone, expect the county archaeologist to ask for a desk-based assessment before the application is determined, and expect a written scheme of investigation to be conditioned if permission follows. The archaeological priority area planning process runs on its own timetable, and it is the one part of the evidence base that can add months to a programme if it is picked up late.
The advice does not come from the case officer. It comes from an archaeological adviser employed by the county council, a unitary authority or, in Greater London, by Historic England's Greater London Archaeological Advisory Service.
How councils map archaeological sensitivity
Greater London boroughs use archaeological priority areas, tiered by significance and mapped borough by borough. Outside London the same idea appears under different names: areas of archaeological interest, areas of archaeological potential, or simply a constraint layer in the local plan proposals map.
The mapping is derived from the historic environment record, which holds known sites, findspots, historic landscape characterisation and the results of previous investigations. Absence from the map is not absence of archaeology. Large areas of England have never been systematically surveyed, and a greenfield site with no recorded features can still produce a Bronze Age enclosure under the topsoil.
Scheduled monuments sit in a different regime altogether. Works affecting them need scheduled monument consent from the Secretary of State under the Ancient Monuments and Archaeological Areas Act 1979, which is separate from planning permission and takes its own time.
Historic environment record searches
A historic environment record search is the first step and costs comparatively little. It returns recorded monuments and findspots within a defined radius, previous archaeological events and their results, historic landscape characterisation, and any designations.
Most records are held by county councils, and in two-tier areas that means the county holds the archaeology while the district determines your application. The division of consultee roles in two-tier areas explains why a response can take three weeks to reach the file.
Order the search before the layout is fixed. Where the record shows a cropmark complex on the eastern half of the site, moving the built form west is free at concept stage and impossible after the drainage strategy is designed.
Charges and turnaround differ between records. Some provide data free to the public and charge for commercial searches. Budget a fortnight.
When a desk-based assessment is asked for
National policy requires an applicant to describe the significance of any heritage assets affected, including any contribution made by their setting, and where a site includes or has the potential to include heritage assets with archaeological interest, to submit an appropriate desk-based assessment and, where necessary, a field evaluation.
That is the wording councils validate against. A local validation list will normally require an Archaeological Desk-Based Assessment for sites in a mapped sensitivity zone, for sites above a stated area threshold, and for any development involving substantial ground disturbance in a historic settlement core.
The assessment draws together the record search, historic mapping, aerial photography, geotechnical information, previous land use and an assessment of the survival of deposits. Its conclusion should state the potential for each period, the likely significance of any remains, and the impact of the proposal, ending with a recommendation on whether evaluation is needed.
Councils usually expect a suitably qualified author working to the professional standards published by the Chartered Institute for Archaeologists, and professional review is strongly advised.
Evaluation by trial trenching, and its timing
Where the desk-based assessment identifies potential that cannot be resolved from documents, the adviser will ask for field evaluation before determination. Geophysical survey usually comes first, then trial trenching sampling a percentage of the site.
Programme it realistically. A trenching evaluation needs a written scheme agreed in advance, a contractor with availability, machine time with an archaeologist supervising, recording, a report and then the adviser's response. Six to ten weeks is a fair allowance for a modest site, longer in winter and longer when the ground is waterlogged.
The reason evaluation happens before determination rather than after is simple. The council needs to know what is there to decide whether the harm is acceptable, and conditions cannot cure a decision made without that information. An Archaeological Field Evaluation submitted with the application, rather than promised by condition, removes the single biggest cause of delay on sensitive sites.
Where remains of national significance are found, the position changes completely. Substantial harm to or loss of assets of the highest significance should be wholly exceptional, and a scheme may need to be redesigned around what has been discovered.
Written scheme of investigation conditions
Where remains are present but not of a significance warranting preservation in situ, the usual outcome is preservation by record, secured by a condition requiring a written scheme of investigation approved before works begin.
The scheme sets out the mitigation strategy: excavation, strip map and sample, or a watching brief. It also covers the post-excavation programme, which is the part clients forget. Finds processing, specialist analysis, radiocarbon dating where appropriate, publication and deposition of the archive with a museum all sit inside that condition, and the archive deposit can require a fee.
Three practical points. Get the scheme drafted by your archaeological contractor and agreed with the adviser before the condition falls due. Make sure the condition wording distinguishes the fieldwork from the post-excavation programme, so that a completed dig does not leave you unable to discharge. And check whether the receiving museum is currently accepting archives, because several are not.
Programming archaeology around the build
Archaeology fits the programme better than most people expect, provided it is sequenced properly.
- Order the historic environment record search at feasibility stage.
- Commission the desk-based assessment alongside the initial layout.
- Undertake geophysical survey and any evaluation before submitting.
- Agree the written scheme of investigation during determination.
- Carry out mitigation fieldwork as the first activity on site, before enabling works.
- Allow for post-excavation and archive deposition after practical completion.
Fieldwork before enabling works matters. Once a site compound is built and a piling rig is booked, an unexpected discovery costs far more than the same discovery found in an open field in March. And winter trenching in clay is miserable, slow and expensive, so plan the fieldwork for the drier months where the programme allows.
Budget for the adviser's response time as well as the fieldwork. An evaluation report submitted in the last week of the determination period still needs the county archaeologist to read it, and a busy adviser covering forty districts will not turn it round in three days. Send it early, and send it to the case officer and the adviser at the same time.
To scope the heritage and archaeology documents your site is likely to need, browse the report types by category and start from your site constraints.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Who gives archaeological advice on a planning application?
An archaeological adviser employed by the county council or unitary authority, and in Greater London the Greater London Archaeological Advisory Service within Historic England. The case officer relies on that advice rather than forming their own view, which is why the response can take several weeks to reach the file.
Does a clear historic environment record mean no archaeology?
No. The record holds what has been reported and investigated, and large areas have never been systematically surveyed. A greenfield site with no recorded features can still contain buried remains, which is why sensitivity mapping is a starting point rather than an answer.
Why must evaluation happen before determination?
Because the council needs to understand what is present before it can judge whether the impact is acceptable. A condition cannot cure a decision taken without that information. Submitting evaluation results with the application removes the most common cause of delay on archaeologically sensitive sites.
What does a written scheme of investigation cover?
The mitigation strategy, usually excavation, strip map and sample, or a watching brief, plus the post-excavation programme. That programme includes finds processing, specialist analysis, publication and deposition of the archive with a museum, which can carry its own fee. Draft it with your contractor before the condition falls due.
How long should I allow for trial trenching?
Six to ten weeks is a fair allowance for a modest site, covering the agreed written scheme, contractor availability, machine time, recording, reporting and the adviser's response. Allow longer in winter and on waterlogged ground, and longer again where the first trenches produce unexpected results.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.