Chance archaeological finds and the Treasure Act

If your groundworker finds something during construction, stop work in that part of the site, do not move the object any further, photograph it where it lies, and tell the county archaeologist the same day. If it looks like gold, silver or a group of old coins, you also have a legal duty to report it to the coroner within 14 days under the Treasure Act 1996, and failing to do so is a criminal offence.

That is the short version, and for most self-builders it is all that is needed. The longer version matters because the difference between a two day delay and a three month one is usually decided in the first afternoon.

The first hour on site

Isolate the area rather than the whole site. Cordon off a working margin around the find, move plant away from it, and stop excavation in that zone only. Work elsewhere can usually continue, and stopping everything is the most common overreaction.

Do not clean the object, do not try to identify it by digging around it, and do not let anyone take it home. Context is most of the archaeological value, and an object lifted out of the ground and pocketed has lost the information that made it worth reporting.

Then make two calls. The first is to the archaeological adviser to your local planning authority, usually the county archaeologist or the Historic Environment Record officer. The second is to your own archaeological contractor if a written scheme of investigation is already in place, because the scheme will say what happens next.

If what has been uncovered appears to be human remains, call the police first and stop work in that area completely. They will decide whether it is a modern matter for the coroner or an archaeological one, and removing human remains needs a licence from the Ministry of Justice in either case.

Reporting obligations for treasure

The Treasure Act 1996 creates a specific duty. Where a person finds an object they believe or have reasonable grounds to believe is treasure, they must notify the coroner for the area within 14 days, beginning with the day after the find or the day they first come to believe it is treasure.

The main categories in section 1 are:

• any object other than a coin, at least 300 years old when found, with at least 10 per cent by weight of gold or silver
• two or more coins from the same find, at least 300 years old, with at least 10 per cent precious metal
• ten or more coins from the same find that are at least 300 years old, whatever the metal
• objects found in the same place as, or previously with, an object that is treasure

Designation orders have added further classes over the years, including base metal prehistoric assemblages and, more recently, exceptionally significant metal objects over 200 years old. The current list is on legislation.gov.uk and it is worth checking rather than working from a summary.

The duty falls on the finder personally. In practice the site manager reports on behalf of the operative who made the find, and the practical route is through the local Finds Liaison Officer of the Portable Antiquities Scheme, who will pass the report to the coroner and arrange for the object to be examined.

Who owns other archaeological material

Treasure vests in the Crown, subject to prior interests. Everything else does not.

Archaeological material that is not treasure generally belongs to the landowner, which on a self-build plot usually means you. That sounds like good news and rarely is. A Roman ditch, a medieval kiln base or a scatter of pottery has no market value and considerable cost attached, because the planning system expects the information to be recovered and published.

Where a find turns out to be of national importance, the Secretary of State can schedule the site under the Ancient Monuments and Archaeological Areas Act 1979 on the advice of Historic England. Scheduling does not stop a planning permission taking effect, but it does mean that any works affecting the monument need scheduled monument consent as well. That is a serious outcome and a rare one.

The finds liaison officer, the coroner and valuation

The Finds Liaison Officer records the find and its location, and where the object may be treasure the report goes to the coroner. A museum may then express an interest in acquiring it, in which case an independent valuation is carried out and a reward is normally shared between the finder and the landowner. If no museum wants it, the object is usually disclaimed and returned.

None of that process pays for the delay on site. It runs in parallel with construction and on a different timescale, which is why the ownership question and the programme question should be kept separate in your own planning.

Whether work has to stop, and for how long

There is no general power for anyone to stop construction because undesignated archaeology has been found. The controls come from three places: a planning condition on your permission, the Treasure Act duty in respect of the object itself, and the criminal offences that attach to a scheduled monument.

Most residential permissions on sites with any archaeological potential carry a condition requiring a written scheme of investigation, agreed before commencement, with a watching brief or evaluation during groundworks. That scheme is what sets the procedure, including the unexpected discovery clause and the period allowed for recording. Where such a condition exists, breaching it puts the permission at risk, so the honest answer to how long work stops is: as long as the agreed scheme says.

Where there is no condition and no scheduled monument, the legal position is looser and the commercial position is not. An authority that learns of an unreported discovery can and does use it when considering later applications, and the cost of an emergency excavation arranged in a hurry is higher than one arranged in advance.

What an unexpected discovery costs

National policy places the cost of recording on the developer, so the bill for evaluation, excavation and reporting falls to the applicant. There is no published scale for this, and quotations vary by depth, ground conditions, the complexity of the deposits and the season.

The parts people forget are at the end rather than the beginning. Once the fieldwork is finished, the post-excavation assessment, archive and publication stage still has to be funded and completed, and many planning conditions are not discharged until the archive is deposited. Budget for the whole sequence rather than the digging.

Contract and insurance provisions worth having

Standard building contracts include an antiquities provision. It typically requires the contractor to stop work in the affected area, protect the object and inform the employer, and it usually gives the contractor an extension of time and a claim for loss and expense. In other words, the risk sits with you.

Three things are worth doing before work starts. Read the antiquities clause in your contract and understand who carries the delay. Check whether your delay in start-up or contract works cover excludes archaeological delay, because many policies do. And agree a rate and a call-off arrangement with an archaeological contractor in advance, so that the response time is measured in days rather than weeks.

Reducing the risk before the diggers arrive

An Archaeological Desk-Based Assessment searching the Historic Environment Record, historic mapping and aerial photography is the cheapest way to find out whether your plot sits on anything known. On a site with potential, a pre-determination trial trench evaluation converts an unknown into a priced item before you commit to a programme.

Where the works involve an existing building rather than open ground, the equivalent exercise is recording before demolition or conversion, and a Heritage Statement submitted with the application is the document that explains the significance you are affecting.

And talk to the county archaeologist at pre-application stage. Their advice shapes the condition, and a condition you helped write is one you can discharge.

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.