A contract works extension on a UK PI policy widens cover to include the cost of rectifying, removing or making safe defective work where the professional’s negligent design or advice has caused the defect. It does not turn PI into construction all risks (CAR) cover; the extension responds to consequential rectification costs that flow from a covered professional liability rather than direct damage to the works themselves.
What the contract works PI extension means
In the standard PI insuring clause, the policy responds to “civil liability” arising from the conduct of the insured’s professional business. The classic claim is for financial loss caused to a third party by negligent advice or design — the loss flowing from the client having to repair, replace or do without something that should have worked.
The grey area is the rectification cost itself. If a structural engineer’s design specifies the wrong steel grade and a beam has to be replaced before completion, the cost of replacing the beam is partly damage to the works (a CAR issue) and partly a consequence of the negligent design (a PI issue). Insurers have long argued about which policy responds in which circumstances, and the contract works extension is the wording response.
The extension extends PI cover to:
- The cost of removing the defective design element from the works
- The cost of installing the corrected design
- Consequential costs of disruption, delay and additional supervision
- Sometimes, the cost of inspecting other potentially affected parts of the works
- Sometimes, the cost of demolition and reconstruction where the defect is structural
The extension does not extend cover to:
- Damage to the works caused by causes unrelated to the professional’s negligence (fire, theft, weather, contractor error not flowing from the professional’s design)
- The contractor’s costs of building the works in the first place (cost-of-the-bargain claims)
- Cost overruns unrelated to a covered design defect
- The professional’s own time spent rectifying its design
The extension is most commonly given to engineers, architects and design-and-build consultants. It is rarely given to accountants, solicitors or non-construction consultants.
How the contract works extension works in practice
When a defect emerges and the cause is contested, the contract works extension allows the PI insurer to respond without waiting for the CAR position to be resolved. In a typical defect notification:
Stage 1 — defect identified. A defect is discovered during construction or shortly after practical completion. The contractor and client investigate; the professional is notified and notifies its PI insurer as a circumstance.
Stage 2 — cause investigated. The investigation establishes whether the defect is a design issue (PI), a workmanship issue (contractor), a materials issue (supplier), or a combination. Where the cause is mixed, the parties typically agree apportionments.
Stage 3 — rectification scoped. The cost of rectification is scoped. This includes the direct cost of removing and replacing the defective element, the consequential costs of access, supervision, disruption to other trades, and the cost of investigating whether other parts of the works are affected.
Stage 4 — PI extension responds. Where the cause is held to be the professional’s negligent design, and the contract works extension is in place, the PI policy responds to the rectification cost subject to the sub-limit and excess. Without the extension, the PI policy might decline part of the cost on the basis that it is damage to the works rather than a covered third-party loss.
The CAR policy on the same project may also respond if its cover triggers — for instance if a structural collapse occurs during construction. In a serious case both policies may be drawn upon and the eventual recovery allocation is negotiated between insurers.
Worked example with realistic numbers
A consulting structural engineering practice in Bristol with £420,000 of fee income carries a £2m each-and-every PI policy with a contract works extension at a £500,000 sub-limit and a £5,000 each-and-every excess. The practice designs the structural frame for a four-storey office development.
Two months before practical completion, the contractor identifies that the engineer’s design under-specified the bolt grade in a critical primary connection. Independent investigation confirms the design error. The contractor estimates rectification cost at £215,000: £140,000 to remove and replace the affected connections across the frame, £55,000 in consequential trade disruption (mechanical and electrical work has to be stripped back from the affected zone), and £20,000 in additional supervision and engineering inspection.
The PI insurer accepts the notification. The contract works extension responds within its £500,000 sub-limit. The insurer pays £210,000 (£215,000 less the £5,000 excess). The engineering practice does not have to fund the rectification from its working capital.
Without the contract works extension, the insurer might have argued that the bolt-replacement cost was damage to the works rather than a covered civil liability — passing the £140,000 element to the CAR insurer or to the contractor’s own resources, and leaving the engineer with a more complex claim journey.
When this matters most
The extension matters most for design professionals working on construction projects where defective design can be expected to produce rectification claims of meaningful size.
Consulting engineers — structural, civil, MEP and geotechnical. The extension is particularly relevant where the engineer’s design drives the works package and a design defect implies direct rectification.
Architects with design responsibility — particularly where the architect specifies products or systems with technical performance requirements. A specification that turns out to be unsuited to its environment can produce direct rectification cost as well as consequential loss.
Design-and-build subcontractors — including specialist subcontractors taking design responsibility for a particular package (façade, MEP, structural steelwork, modular construction). The extension is often essential because the subcontract package is the rectification target.
Building services consultants — net-zero designers, M&E coordinators, building physics consultants. As building services have become more integral to project delivery, the consequential cost of rectifying a flawed services design has grown.
Project managers and contract administrators — where their certification or instruction has caused the works to proceed in a way that requires later rectification.
The extension is less relevant to professionals whose deliverables are advisory rather than constructional — accountants, lawyers, IFAs, generalist consultants. Their losses flow as financial damage to clients rather than as rectification of physical works.
Common variations and market wording
The extension is one of the less standardised parts of construction-focused PI cover. Wordings vary in several ways.
Sub-limit size. Sub-limits typically run from £250,000 to £1m within the main policy limit. Some insurers will offer the full policy limit as the sub-limit for engineers with strong track records. The sub-limit caps total contract works claims in the policy year.
Trigger. Most wordings trigger on “negligent design or advice”; some require “negligent breach of professional duty”; a few extend to “any cause arising from the conduct of the professional business”. The narrower the trigger, the more contested the response in mixed-cause defects.
Mitigation costs. Some wordings explicitly include the cost of mitigation work the professional commissions to reduce a larger eventual claim (interim shoring, monitoring, additional inspection of unaffected zones). Others require the insurer’s prior consent before mitigation costs are incurred.
Demolition and reconstruction. A few wordings expressly exclude demolition and reconstruction costs even where they arise from the covered design defect. Where the works being designed are major structures, the cap on demolition cost cover can leave a serious uninsured exposure.
Inspection and investigation. Some wordings cover the cost of inspecting other parts of the works to identify whether the defect is replicated. This can be valuable on schemes where one design element has been replicated across multiple buildings or floors.
Listed/heritage premises. Special-case treatment is sometimes given to works on listed buildings or heritage structures, where rectification cost can be materially higher than for new build. The extension may be sub-limited further for such projects.
Building Safety Act 2022 interaction. Following the Building Safety Act, dutyholder responsibilities on higher-risk buildings have produced new design-responsibility claims. Wordings have not fully caught up; some insurers now apply specific sub-limits or exclusions for higher-risk buildings under the Act.
Related concepts
- Breach of contract cover — relevant where the rectification is also a breach of warranties given by the professional in the appointment.
- Civil liability extension — the broad cover that responds where the contract works extension is not in place.
- Intellectual property infringement PI cover — relevant where re-use of drawings or design rights overlaps with rectification of construction works.
Frequently asked questions
Is a contract works extension the same as construction all risks?
No. Construction all risks (CAR) is a separate project insurance policy taken out by the contractor or client, which covers physical damage to the works, materials and plant during construction from defined causes. The contract works PI extension covers the cost of rectifying defects caused by the professional’s negligent design or advice. CAR responds to physical loss; the PI extension responds to professional liability that produces rectification cost.
Does the contract works extension cover damage caused by the contractor?
No, only where the damage flows from a covered professional liability. If the contractor mis-installs a correctly designed element and the element has to be re-done, that is the contractor’s issue and the CAR policy may respond. If the contractor installs in accordance with a negligently flawed design, and the design is the cause, the PI extension responds.
What is the typical sub-limit?
Sub-limits commonly run from £250,000 to £1m within the main policy limit. A few wordings give the full policy limit to contract works claims. The sub-limit caps total contract works claims in the policy year and erodes the main limit when it is drawn down. The sub-limit is one of the first numbers to check at renewal for engineers and architects.
Does the extension cover delay damages payable to the client?
Sometimes, where the delay was directly caused by rectification of the covered design defect. The delay cost has to be reasonable and proportionate to the rectification needed. Liquidated damages payable to the client under the main building contract are insurable as a covered loss flowing from the professional’s negligence, where the wording does not exclude liquidated damages separately. Some wordings do exclude liquidated damages — read the wording.
Is demolition and reconstruction covered?
In most modern wordings, yes, where the defect cannot be rectified without demolition and the cost is reasonable. A few wordings cap demolition cost separately. Where the design is for major structural elements that would require substantial reconstruction to rectify, an express confirmation that demolition is within cover is worth obtaining.
Does the extension apply to higher-risk buildings under the Building Safety Act?
Insurer practice on higher-risk buildings has been cautious since the Act came into force. Some wordings now apply specific sub-limits or exclusions for design work on higher-risk buildings (broadly, residential buildings of 18 metres or more, or seven storeys). Disclose higher-risk building work explicitly at renewal and confirm the position on the contract works extension.
Does the extension cover failure of materials specified by the engineer?
Where the engineer’s specification turned out to be unsuited to the actual conditions, and rectification is required, the extension typically responds. Where the issue is product failure by the manufacturer of a properly specified product, the loss is more naturally a product liability claim against the manufacturer; the engineer may still face a claim for failing to warn or inspect, and the extension responds to that.
How does the contract works extension interact with collateral warranties?
Collateral warranties given by the professional to funders, tenants or purchasers can extend the universe of claimants on a defect. The contract works extension responds whether the claim comes from the original client or a warranty beneficiary, provided the underlying negligence is the same. Check that the wording does not restrict cover to claims by the original client only.
{
"@context": "https://schema.org",
"@type": "Article",
"headline": "Contract Works PI Extension — What It Covers and Where It Doesn't Reach",
"description": "How the contract works extension on UK PI policies works — what's covered, the overlap with construction all risks, sub-limits and when the extension is worth requesting.",
"author": {
"@type": "Organization",
"name": "Apex Insurance Brokers Ltd"
},
"publisher": {
"@type": "Organization",
"name": "Apex Insurance Brokers Ltd"
},
"datePublished": "2026-05-29",
"dateModified": "2026-05-29",
"image": "contract-works-pi-extension-hero.jpg"
}
{
"@context": "https://schema.org",
"@type": "DefinedTerm",
"name": "Contract works PI extension",
"description": "An extension on a UK professional indemnity policy that widens cover to include the cost of rectifying, removing or making safe defective work where the professional's negligent design or advice has caused the defect. Usually subject to a sub-limit within the main policy limit and most commonly given to engineers, architects and design-and-build consultants.",
"inDefinedTermSet": {
"@type": "DefinedTermSet",
"@id": "/glossary/",
"name": "Apex Insurance Brokers PI Glossary"
}
}
{
"@context": "https://schema.org",
"@type": "FAQPage",
"mainEntity": [
{
"@type": "Question",
"name": "Is a contract works extension the same as construction all risks?",
"acceptedAnswer": {
"@type": "Answer",
"text": "No. Construction all risks (CAR) is a separate project insurance policy that covers physical damage to the works from defined causes. The contract works PI extension covers the cost of rectifying defects caused by the professional's negligent design or advice. CAR responds to physical loss; the PI extension responds to professional liability that produces rectification cost."
}
},
{
"@type": "Question",
"name": "Does the contract works extension cover damage caused by the contractor?",
"acceptedAnswer": {
"@type": "Answer",
"text": "No, only where the damage flows from a covered professional liability. If the contractor mis-installs a correctly designed element, that is the contractor's issue. If the contractor installs in accordance with a negligently flawed design, the PI extension responds."
}
},
{
"@type": "Question",
"name": "What is the typical sub-limit?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Sub-limits commonly run from £250,000 to £1m within the main policy limit. A few wordings give the full policy limit to contract works claims. The sub-limit caps total contract works claims in the policy year and erodes the main limit when it is drawn down."
}
},
{
"@type": "Question",
"name": "Does the extension cover delay damages payable to the client?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Sometimes, where the delay was directly caused by rectification of the covered design defect. Liquidated damages payable to the client under the main building contract are insurable as a covered loss flowing from the professional's negligence, where the wording does not exclude liquidated damages separately."
}
},
{
"@type": "Question",
"name": "Is demolition and reconstruction covered?",
"acceptedAnswer": {
"@type": "Answer",
"text": "In most modern wordings, yes, where the defect cannot be rectified without demolition and the cost is reasonable. A few wordings cap demolition cost separately. For major structural elements an express confirmation that demolition is within cover is worth obtaining."
}
},
{
"@type": "Question",
"name": "Does the extension apply to higher-risk buildings under the Building Safety Act?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Insurer practice on higher-risk buildings has been cautious since the Act came into force. Some wordings apply specific sub-limits or exclusions for design work on higher-risk buildings. Disclose higher-risk building work at renewal and confirm the position on the contract works extension."
}
},
{
"@type": "Question",
"name": "Does the extension cover failure of materials specified by the engineer?",
"acceptedAnswer": {
"@type": "Answer",
"text": "Where the engineer's specification turned out to be unsuited to the actual conditions and rectification is required, the extension typically responds. Where the issue is product failure by the manufacturer, the engineer may still face a claim for failing to warn or inspect, and the extension responds to that."
}
},
{
"@type": "Question",
"name": "How does the contract works extension interact with collateral warranties?",
"acceptedAnswer": {
"@type": "Answer",
"text": "The contract works extension responds whether the claim comes from the original client or a collateral warranty beneficiary, provided the underlying negligence is the same. Check that the wording does not restrict cover to claims by the original client only."
}
}
]
}
About Apex Insurance Brokers Ltd
Apex Insurance Brokers Ltd is a Bristol-based UK insurance broker specialising in professional indemnity cover for regulated and non-regulated professional firms. Apex is authorised and regulated by the Financial Conduct Authority, firm reference number 724952, and is registered at Companies House under number 07014570. Contact: info@apexinsurancebrokers.co.uk or 0117 325 0027.
Last reviewed: May 2026 by Apex Insurance Brokers Ltd.
Important: this article is general information, not advice on your specific circumstances. For advice on PI insurance for your firm, contact us on 0117 325 0027 or info@apexinsurancebrokers.co.uk.