Aipedia: Quantity surveyors

AI valuing variations and compensation events: the QS side

Aipedia, by the Apex broking team · Last reviewed 2026-10-30

A quantity surveyor can use AI to price JCT variations and NEC compensation event quotations, but the valuation must follow the contract's own rules, not the tool's defaults. Errors in these figures move real money between employer and contractor and often end in disputes.

Part of: AI in quantity surveying

In short

AI tools can read instructions, draft quantities and suggest rates for JCT variations and NEC compensation event quotations. The risks are rates applied outside the contract's valuation rules, errors in defined cost and fee calculations, and quotations or assessments produced after contractual time limits have passed. These are the QS's problems whether working for the employer or the contractor, separate from the project manager's change control role. Under the RICS AI standard, a named surveyor must make a written reliability decision on outputs (4.2). PI usually treats valuation errors as negligence, subject to the policy terms.

How QSs use AI on change

Change is where much of a QS's commercial work lies. On a JCT contract, the QS values variations using the contract's valuation rules: bill or schedule rates where the work is similar, adjusted rates where conditions differ, and fair rates or daywork only where the rules allow. On an NEC contract, compensation events are assessed on their effect on defined cost plus the fee, usually through quotations, and the time and cost effects are assessed together.

AI tools now read instructions and drawings, suggest the relevant rates, assemble defined cost from records and draft quotations or assessments. Contractor QSs use them to price change quickly; employer QSs use them to check what has been submitted. The project manager's side of change control, including issuing instructions and keeping registers, is covered at AI in change control for project managers.

The duties that apply

Several existing duties apply to this work:

Contract rules: the valuation method is set by the contract, including any amendments. A tool that defaults to market rates or a generic method is not following the contract.
RICS AI standard 4.2: a named, appropriately qualified surveyor records whether each priced output is reliable, with dip sampling where pricing is automated.
4.1: ask the supplier how rates are selected and whether contract-specific rules can be configured.
3.1: rates and defined cost records are commercially sensitive; get express prior written consent before uploading them.
Rules 2 and 3: the RICS Rules of Conduct require competence in the form of contract being administered.

What can go wrong

Common ways this goes wrong include:

Wrong valuation rule: a variation is priced at fresh market rates where the contract required bill rates, or the reverse.
Defined cost errors: people or equipment costs are included that the contract excludes, or the fee is applied twice.
Time limits: a quotation or assessment is prepared after the contract's period has passed, because the tool did not track notification dates.
Time and money split: a compensation event is priced without assessing its effect on the programme, or with a programme that is out of date.

Illustrative: a contractor's QS uses AI to price a series of NEC compensation events from site records. The tool includes some costs the amended contract excludes and misses that several events were notified late. The project manager rejects the quotations and makes its own lower assessments. The contractor loses the opportunity to challenge some of them in time and says its QS was negligent.

How PI usually responds

A claim that a QS valued change negligently is usually handled as professional negligence under the RICS Approved Minimum Wording, subject to the policy terms. Insurers commonly ask whether the client suffered a real loss, because a valuation error may be correctable through the contract's own mechanisms. Missed time limits are harder, as the client may have lost a right altogether.

Appointments on larger projects may set specific PI requirements for QSs, sometimes higher than the RICS minimums. Our guide to JCT and NEC appointment PI requirements sets out what to look for.

Practical controls

These steps reduce the risk:

Configure or brief the tool on the actual contract, including the valuation rules and any amendments.
Keep a register of notification and quotation dates outside the AI tool, reviewed weekly.
Check defined cost against the contract's schedule of cost components, line by line for high-value events.
Where the tool cannot show which record supports a figure, treat the figure as unverified until a person has traced it.
Price time and money together and check the programme used is current.
Record the named QS's sign-off before submission.

How Apex helps

Apex arranges PI for quantity surveyors on both the employer and contractor side. A broker can review whether your policy and limit match your appointments and how AI-assisted pricing is described. Related: AI loss and expense claims, AI in final accounts, the QS PI guide and the QS AI hub.

Sources

Frequently asked

Does the QS or the project manager carry the risk of AI errors in compensation events?

It depends on who did what. Under NEC, the project manager assesses compensation events, while QSs often prepare quotations for contractors or check them for employers. Each is responsible for their own advice, and each needs PI that fits their role.

Can an AI tool track contractual time limits for me?

It can help, but the RICS AI standard requires professional scepticism and a named surveyor's reliability decision. Missed time limits can extinguish a client's rights, so keep an independent date register checked by a person.

Is a contractor-side QS covered by RICS-compliant PI?

If the QS works in an RICS-regulated firm, the firm's RICS-compliant PI should cover its professional services, subject to the terms and the business description. An employed QS in a contracting business is usually covered by the employer's arrangements, not their own PI.

Check your PI covers how you use AI

Tell us about your firm and the work you do. A broker will review how your current PI treats AI-assisted work, or arrange new cover. No fee for a quote. Or call 0117 325 0027.

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Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Registered in England and Wales, company number 07014570. This page is general information about how AI is used in the profession and how insurance may respond. It is not legal, regulatory or insurance advice on your circumstances, and it does not guarantee that cover will be available or on what terms.