Archaeological Desk-Based Assessment outline to CIfA

An archaeological desk based assessment outline that satisfies a county archaeologist follows the standard and guidance published by the Chartered Institute for Archaeologists, and the part that gets skipped is the records search. The assessment has to state which sources were consulted, over what study area, on what date, and what each returned. A document that cites the Historic Environment Record and nothing else has not done the work, and a curator who reads it will ask for a field evaluation rather than argue about method.

The structure below follows the sequence a curator expects: what was searched, what the records show, what is likely to be there, how significant it would be, what the proposal would do to it, and what should happen next.

Study area and the records searched

Open by defining the study area and justifying it. A 1 km radius from the site boundary is conventional for a small scheme, extended where a known monument, a river terrace or a linear feature makes a wider view necessary, and reduced only with a reason. State the radius, show it on a figure, and say why.

Then list the sources with the date each was consulted.

• The Historic Environment Record for the county or unitary authority, with the search radius and the reference number of the search
• The National Heritage List for England for listed buildings, scheduled monuments, registered parks and gardens and battlefields
• The Historic England Archive for aerial photography and previous survey records
• The Portable Antiquities Scheme database for recorded finds within the study area
• Published and unpublished reports on previous investigations, including grey literature held in national archaeological archives
• Historic mapping from the earliest available estate, enclosure and tithe maps through successive Ordnance Survey editions
• Geological and soils mapping, and any available geotechnical or borehole data for the site
• Remote sensing data including LiDAR where available
• A site walkover with photographs

Two omissions recur. Geotechnical data from the site's own ground investigation is often available and almost never used, yet it tells you the depth of made ground and whether earlier horizons survive. And the county's own development plan policies and any archaeological priority area mapping should be recorded, because they set what the authority will require.

Historic map regression

Map regression is evidence, not decoration, so present it as a sequence of extracts at a consistent scale with the site boundary overlaid on each.

The purpose is to establish land use through time and, above all, the history of ground disturbance. A field that became a brickworks in 1890 and a car park in 1965 has a very different survival prospect from one that stayed in pasture. Record what each map shows about buildings, boundaries, extraction, drainage and levelling, and draw a conclusion about truncation rather than leaving the reader to infer it.

Where the earliest map is late, say so. A site with no cartographic coverage before the 1840s has a gap that only excavation or documentary research fills.

Previous investigations nearby

This section is where a well-researched assessment separates itself, because it converts general potential into specific expectation.

For each relevant investigation within the study area, record its location and distance from the site, the type of work, the date, the depth and extent investigated, and what was found or not found. Negative results matter as much as positive ones: three evaluations on adjoining fields that found nothing is a material fact about your site's likely potential.

Cross-reference each investigation to the figure showing the study area, and say plainly whether the pattern of previous work makes remains on your site more or less likely.

Baseline archaeological potential by period

Work through the periods in order, and for each one say what is known in the study area, what that implies for the site, and how confident you are.

The conventional sequence runs Palaeolithic and Mesolithic, Neolithic, Bronze Age, Iron Age, Roman, early medieval, medieval, post-medieval, and modern including twentieth-century military remains. Not every period needs a paragraph, and an honest assessment will say that the evidence for a period is absent rather than padding the section.

Two things make this part useful rather than a literature review. Relate each period to the site's topography and geology, since river gravels, spring lines, dry valleys and hilltops each carry characteristic potential. And end with a clear statement of potential by period, expressed as low, moderate or high with the reasoning, because that is what the curator will read.

An illustrative example. A 1.8 ha site on second river terrace gravels, 400 m from a known Iron Age and Roman settlement recorded from aerial photography, with three cropmark enclosures in the study area and no previous intrusive work on the site itself. Historic mapping shows continuous arable use with no extraction. The conclusion is high potential for later prehistoric and Roman remains, moderate for medieval field systems, and good survival below a shallow ploughsoil. The scenario is illustrative.

Significance of likely remains

Significance is assessed even where remains are only predicted, because the policy tests turn on it. National policy and Historic England guidance frame heritage significance through evidential, historical, aesthetic and communal value, and for buried archaeology the evidential value usually dominates.

Set out for each category of likely remains what its significance would be and at what level: national, regional or local. Note whether any part would be a heritage asset of the highest significance, since scheduled monuments and non-designated assets of equivalent significance attract the strongest protection.

Be explicit about the distinction between a designated asset and a non-designated one. The policy test for substantial harm to a designated asset of the highest significance is different from the balanced judgement applied to a non-designated asset, and the assessment should name which test the decision-maker will be applying. Where standing buildings are also affected, that analysis belongs in a Heritage Statement rather than here, in the same way that a heritage statement for a listed shopfront deals with fabric rather than buried remains.

Impact of the proposal below ground

This section needs the engineering drawings, and it is the section most often written without them.

Work through every source of ground disturbance: foundation type and depth, whether piling is proposed and at what spacing, ground beams, basements and lift pits, service trenches and their depths, attenuation tanks and soakaways, road and hardstanding construction depth, landscape excavation and tree pits, and any level change from cut or fill. Then compare those depths with the depth at which remains are expected to survive, established from the previous investigations and the geotechnical data.

The conclusion should be expressed as an area and a proportion. Stating that foundations and drainage would disturb roughly 35 per cent of the site to a depth of 1.2 m is useful. Stating that there would be an impact on any archaeology present is not.

Preservation in situ options belong here too. Raising levels, using a piled solution with a low displacement footprint, relocating attenuation to an area of known truncation, or moving a road alignment can all reduce impact, and a proposal that shows the design responding to the archaeology is treated very differently from one that does not.

Recommendations for further work

Close with a proposal, not a request for instructions.

1. Geophysical survey where the geology allows it and the expected remains would produce a response.
2. Trial trench evaluation, with an indicative trench percentage and layout, targeted on anomalies and on blank areas for control.
3. Whether either should be done before determination, which many authorities require where potential is high.
4. A written scheme of investigation for the agreed work, to be approved by the curator.
5. The likely form of mitigation if remains are found, whether preservation in situ, excavation and recording, or a watching brief.
6. An outline programme, noting that evaluation can usually be done at any time of year but needs access and reinstatement.
7. Publication and archive deposition arrangements.

Pre-determination evaluation is worth addressing directly rather than hoping for a condition. Where an authority's policy requires evaluation before determination, a condition is not available to it, and an application submitted without the evaluation will simply wait. A properly scoped Archaeological Field Evaluation done early is usually faster than arguing about whether it is needed.

One honest uncertainty. Curators differ on trench percentages and on whether geophysical survey is worth commissioning on particular geologies, and a 2 per cent sample that satisfies one county archaeologist will be queried by another. Agree the scope in writing before the contractor mobilises.

Browse all 66 report types on PlanScope to see which heritage and archaeology documents your site is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.