Most homeowners carry out building works without telling their insurer. This is a problem. Standard home insurance policies contain conditions about notifying the insurer of significant alterations or works to the property, and failure to notify can invalidate your policy entirely. If something goes wrong during the works and your insurer discovers it wasn't disclosed, you may have no cover at all.
The insurance implications of renovation work are genuinely underappreciated. This guide covers what you need to do, what specialist insurance exists for the build period, and how to ensure you're covered throughout.
Notifying Your Existing Insurer
The first thing to do when you have a confirmed building project is contact your home insurer and tell them. Do this before work starts. Explain the nature, scale, and duration of the works. Ask them to confirm in writing whether your existing policy continues to provide cover and, if so, under what conditions.
The response varies by insurer and by the scale of the works:
Minor works (decoration, minor bathroom or kitchen refits, no structural changes): most insurers will continue cover with no change, often without even a premium adjustment.
Significant alterations (structural works, extensions, loft conversions): many standard policies either exclude cover for the period of works entirely, or require an endorsement (an addition to the policy) with an additional premium. Others will continue cover but exclude the specific risks created by the building works.
Unoccupied properties: if you're vacating the property during the works, standard home insurance almost always contains provisions about unoccupied periods (typically 30-60 days). A renovation that empties the property for six months will breach these conditions and invalidate your cover unless you arrange specialist unoccupied property insurance.
Site-Specific Insurance
For significant building works, a specialist site insurance policy (also called contract works insurance or self-build insurance) covers the specific risks of the construction period that a standard home policy won't:
Contract works. Covers loss or damage to the works themselves during construction. If a completed structure is damaged by fire, flood, storm, or vandalism before practical completion, this reinstates it. Without it, you bear the cost of rebuilding work that has already been paid for.
Public liability. Your contractor should have their own public liability insurance, but it's prudent to have site public liability cover in your own name as well. If a member of the public or a neighbour is injured or has their property damaged due to your project, this protects you.
Employers' liability. If you're directly employing any workers on site (even casually), you're legally required to have employers' liability insurance of at least £5m. If you're appointing a main contractor, the requirement sits with them. If you're self-managing and directly instructing individual trades, it potentially sits with you. Get advice on this point if you're unsure.
Self-build insurance packages (from providers like Buildstore and Self-Build Zone) typically bundle contract works, public liability, and other site risks into a single policy. For an extension project, a construction-period policy might cost £400-£1,000 depending on the build value and duration.
Check your contractor's insurance, but don't rely solely on it. If your contractor's policy lapses mid-project, or if the claim arises from circumstances their policy excludes, your property is unprotected unless you have your own cover in place.
Unoccupied Property Insurance
If you move out during the build, standard home insurance almost certainly won't cover the empty property for the full duration. Unoccupied property insurance is a specialist product that covers vacant properties for extended periods. Premiums are typically higher than standard cover because vacant properties are statistically more at risk from fire, flood, and vandalism (both because problems go undetected longer and because they're more vulnerable to opportunistic damage).
Conditions typically include regular property inspections (every 7-14 days), keeping utilities on or off as specified, and maintaining basic security. Check the policy conditions carefully: an insurer who discovers that the property was left without a scheduled inspection when a loss occurred will try to use that as grounds to avoid the claim.
Contents and High-Value Items
During a renovation, you may be moving contents between rooms, storing items in a skip or garden, or temporarily placing valuables in storage. Standard contents policies cover items in your home, not in a garden shed, a skip, or a third-party storage unit.
If you're storing valuable items temporarily, check what cover you have for them. You may need to add cover for items temporarily removed from the property, or arrange short-term storage insurance through the storage facility.
Items being fitted into the property (new kitchen units in the garage waiting to be installed, flooring stored on site) are typically treated as contract works rather than contents. They should be covered by your contract works insurance rather than your home contents policy.
Updating Your Policy After Completion
When the works are complete, notify your insurer again. The rebuild cost of your property has increased (sometimes significantly), and your contents may have changed too. A policy taken out on an unextended house will be underinsured once the extension is complete.
Underinsurance is a real problem in building claims. If you insure for £400,000 and the true rebuild cost is £600,000, most policies apply an average clause: they'll only pay 66% of any claim, however large. Get a rebuild cost calculation (RICS publish a house rebuilding cost calculator) and ensure your buildings sum insured reflects the post-completion value.