TL;DR - KEY POINTS
- Home insurance while building an extension must be notified to the insurer or cover can be voided.
- Many policies cap minor works at £25,000 to £75,000 and require separate cover above that threshold.
- Contract works or renovation insurance covers new materials, public liability and existing structure together.
- JCT Insurance Option A, B and C define who insures the existing building and the works during construction.
- Empty property and unoccupied clauses can be triggered during renovations and remove cover for theft or water damage.
UK HOME INSURANCE - BUILDING EXTENSION - 2026
KEY FACTS
- FCA Insurance Conduct of Business rules require insurers to act on notifications of changes in risk during the policy term.
- Standard household policies include a minor works limit, often £25,000 to £75,000, written into the schedule or wording.
- Contractors All Risks insurance is the trade product covering large extensions, conversions and structural works.
- Public liability cover for a builder must be at least £2m, with £5m or £10m common on commercial sites.
- Empty property exclusions usually trigger after 30 or 60 consecutive days unoccupied during major works.
Home insurance while building an extension is one of the most misunderstood areas of UK household cover. Standard home insurance is written for everyday occupation and does not automatically extend to large building works. Failing to notify the insurer, exceeding the minor works limit, or letting the property fall under an empty property clause are the three biggest reasons claims are declined during a renovation. Notifying the insurer, checking the schedule for works thresholds, and arranging a contract works or JCT-compliant policy are the basic steps before the builder starts on site.
Home insurance while building an extension: what to notify
The first call before a project starts is to the existing insurer. Most UK home insurance policies require the policyholder to notify the insurer of any material change in risk during the term, including building works. Insurers either confirm continued cover under the existing policy, apply special endorsements, increase the excess on certain perils, or refuse to continue cover and require the works to be insured separately. Failing to notify the insurer can void cover for the duration of the works and for losses indirectly related to them.
The information the insurer needs typically includes the scope of the works, the start and expected completion date, the value of the works, whether the property will remain occupied, whether scaffolding will be erected, and the contractor's name and public liability cover details. For larger jobs the insurer may also ask for a copy of the building regulations approval and any party wall award.
Where the existing insurer continues cover, the schedule should be updated in writing. A verbal confirmation is rarely sufficient if a dispute arises. Policyholders should keep a copy of the updated schedule and any endorsement letters. The Financial Conduct Authority's Insurance Conduct of Business rules require insurers to deal with notifications promptly and to make their requirements clear in writing.
Minor works limits and what they cover
Most UK home insurance policies include a minor works limit in the schedule. The limit varies by insurer and sits commonly between £25,000 and £75,000. Works within the limit are covered under the existing policy as a low risk continuation of occupation. Internal redecoration, replacement kitchens, single bathroom installations and small electrical jobs usually fall inside the threshold. Single storey rear extensions, loft conversions and structural alterations frequently exceed it.
The minor works limit covers the existing buildings and contents during the works but does not extend to new materials, plant on site, or theft from the contractor's compound. Damage caused by the contractor to the existing structure may be covered by the household policy if the contractor is uninsured, but insurers typically reserve the right to recover from the contractor's public liability insurance through subrogation. This is one reason insurers ask for the contractor's insurance details before continuing cover.
Where the works exceed the minor works limit, the household policy alone is insufficient. The homeowner needs either a renovation insurance product, a contract works policy under the JCT framework, or an arrangement where the contractor's policy covers the existing structure as well as the works. Each route has its own paperwork and limits.
JCT contract insurance options explained
JCT, the Joint Contracts Tribunal, publishes the standard form construction contracts used across UK building works. JCT contracts contain three main insurance options for the works. Option A is used for new build works and requires the contractor to insure the works in joint names of the employer and contractor. Option B is used where the employer insures new works. Option C is used for extensions and alterations to an existing building and requires the employer to insure both the existing structure and the works.
For most domestic extensions, Option C is the practical reality. The homeowner already insures the existing house and must arrange cover that extends to the works in joint names. Some specialist insurers write Option C policies directly for homeowners, while others operate through brokers who package the cover with the household policy. The benefit is a single insurer responding to a loss that affects both the existing house and the new works, removing the dispute about which policy responds first.
Domestic homeowners not using a formal JCT contract still benefit from understanding the framework. The principles map onto how commercial contract works policies are written, and most renovation insurance products on the UK market follow the JCT logic even when the underlying contract is informal.
Contract works and renovation insurance products
Renovation insurance is sold by specialist insurers and brokers under names such as contract works, contractor all risks, or renovation cover. A typical domestic product covers the existing buildings and contents for the duration of the project, the new works including materials on site, public liability of typically £2m to £5m, employers liability if the homeowner directly employs labour, and legal expenses for disputes with the contractor.
Premiums depend on the value of the works, the duration of the project, the type of construction and the postcode. A £150,000 single storey extension over six months might cost £600 to £1,500 to insure depending on the insurer and the risk profile. Higher value or longer projects scale up. Most policies are written for an estimated duration with the option to extend if works overrun, subject to additional premium.
The existing home insurance policy may be cancelled or paused during the contract works policy, depending on the broker arrangement. Some homeowners run both simultaneously to keep claims simpler, others switch entirely. The decision is usually made on advice from the broker and depends on the wording of both policies. A clear written record of who insures what is critical to avoid disputes during a claim.
Empty property and unoccupied risks during works
Major renovations often involve the family moving out for safety or convenience. Once the property is unoccupied for a continuous period, usually 30 or 60 days, standard home insurance triggers the empty property clause. The clause removes cover for theft, malicious damage, escape of water and accidental damage, leaving only fire, lightning, aircraft and explosion. This is a common cause of declined claims during extensions because policyholders do not realise the clause has activated.
Unoccupied property insurance is a separate product designed for empty homes. It provides broader cover than the unoccupied clause on a standard policy but at a higher premium. For renovation periods over a few weeks, unoccupied property insurance combined with contract works cover gives a more complete answer than relying on the household policy. Insurers also expect the property to be secured, water drained down if heating is off, and inspected at least weekly.
The Financial Ombudsman Service publishes decisions on disputes where insurers declined claims during renovations on empty property grounds. The FOS has consistently held that insurers must clearly communicate the unoccupied clause and that policyholders are entitled to a reasonable opportunity to take action. Notifying the insurer about the project at the outset is the simplest way to ensure the right cover sits in place from the first day of works.
Disclaimer: This guide is for information only. Kael Tripton Ltd is not authorised or regulated by the FCA. Nothing on this page constitutes financial advice. Always check current policy terms with your insurer before making decisions.
Frequently asked questions
Do I need to tell my home insurance about a building extension?
Yes, every UK home insurance policy requires notification of building works as a material change in risk. Failing to notify can void cover for losses during the project and for losses indirectly related to it. The call should be made before works start and confirmed in writing on an updated schedule from the insurer.
Does home insurance cover building works at home?
Standard home insurance covers minor works up to a limit set in the schedule, typically £25,000 to £75,000. Major extensions, loft conversions and structural alterations usually exceed the limit and require contract works or renovation insurance. The existing buildings and contents remain insured during the project subject to the insurer's terms.
Who insures an extension under construction?
Under JCT Option C, used for most extensions, the homeowner insures both the existing building and the works in joint names with the contractor. Many specialist renovation insurance products provide this cover. The contractor's public liability cover protects against third party injury and damage caused by the contractor's negligence.
Will my insurance still cover theft from the building site?
Theft from a building site is usually excluded under a standard home insurance policy. Contract works policies cover materials and equipment owned by the homeowner that are on site for incorporation into the works, while the contractor's own tools and plant are covered by the contractor's policy. Securing the site at night and weekends is a condition of most policies.
What if my house is empty during the works?
Empty property clauses trigger after 30 or 60 days unoccupied on most policies. Cover narrows to fire, lightning, aircraft and explosion only, removing theft and water damage cover. Unoccupied property insurance for the duration of the renovation, combined with contract works cover, is the standard arrangement for projects where the family moves out.
How much does extension insurance cost?
A typical domestic extension valued at £100,000 to £200,000 over six months sits at roughly £500 to £1,500 for contract works cover. The price depends on the works value, the duration, the construction method and the postcode. Brokers package the cover with the household policy where the insurer allows it, and quotes are usually obtained before contracts are signed.
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