You’ve had the loft boarded out, the kitchen knocked through, or a wet room fitted downstairs, and somewhere in a drawer is an invoice you never thought to show anyone outside the trade who did the work. Most homeowners only think about whether to tell their insurer about renovations after something has gone wrong — a leak through new plasterboard, or a survey during a sale that turns up work with no paper trail. By then it is too late to fix the one thing that actually matters.
You need to tell your insurer about any structural work, extension, rewiring, replumbing, loft conversion, or change of use before it starts, because an undisclosed “material change” can reduce what an insurer pays out or let them refuse a claim altogether. Redecorating, a like-for-like kitchen refit, or new flooring generally do not need reporting. The line between the two is narrower than most people assume, and it is the insurer’s definition that counts, not yours.
Why insurers care what you build
A buildings insurance quote is priced against the house you told them about at the start: its construction, its size, how it’s used, and its rebuild cost. Extend it, gut it, or convert part of it into a separate living space, and the risk they priced no longer matches the risk they’re covering. That’s not the insurer being difficult. It’s the same reason you wouldn’t expect car insurance bought for a hatchback to still apply once you’ve fitted a different engine.
What you must tell your insurer about
Tell your insurer, in writing, before work starts, if you are:
Extending the property — a side return, rear extension, loft conversion, garage conversion or outbuilding used as living space.
Removing or altering structural walls, including opening up a kitchen-diner.
Rewiring, replumbing, or replacing the consumer unit as part of wider works, rather than a like-for-like repair.
Changing the roof structure or covering, not just re-tiling like-for-like.
Converting the property into flats, an annexe, or a space you’ll let out (Airbnb-style short lets almost always need separate disclosure).
Leaving the property unoccupied for an extended period during the works — most policies define “unoccupied” at 30 or 60 days, and building sites left empty overnight are a common target.
What you usually don’t need to report
New kitchen units or a bathroom suite that doesn’t move pipework or walls.
Redecorating, new flooring, or a new boiler that’s a like-for-like replacement.
Garden landscaping that doesn’t add a structure (a shed under a certain size is often fine — check your policy wording).
Replacing windows or doors like-for-like, as opposed to changing the opening size.
If in doubt, the honest answer is to ask. A five-minute call or a note through your policy’s online portal costs nothing. Finding out the hard way, mid-claim, costs considerably more.
The grey area: small works you assume don’t count
Loft insulation, a new driveway, solar panels, or an EV charger sit in a genuine grey area. None are “extensions” in the everyday sense, but several change the rebuild cost or what’s attached to the property, and some insurers ask about them at renewal. Treat anything involving a contractor, a permit, or a permanent fixture as worth a quick disclosure check.
What actually happens if you don’t tell them
Non-disclosure doesn’t always void a policy outright — UK insurers distinguish between deliberate concealment and an honest oversight. But the practical range of outcomes still runs from a reduced payout, through a proportionate cut based on the premium you should have paid, to the insurer treating the policy as if it never covered the altered part of the property.
Before you start any structural job, assume every insurer will eventually find out, because a claim, a survey, or a mortgage revaluation tends to surface undeclared work at the worst possible moment. Treat a five-minute disclosure call as cheaper than any version of that conversation happening later. Insurers would rather adjust a premium now than argue about a claim in eighteen months, and so would you.
Will telling them put your premium up?
Sometimes, and it’s worth knowing why before you’re surprised by it. A higher rebuild cost, a higher-risk feature like a flat roof or a loft with limited escape routes, or a vulnerable period during works can all nudge a premium up. Just as often, disclosure changes nothing, because the work brings the property up to a better standard.
What you should not do is stay quiet to avoid a premium rise. A modest increase, or none, is a far better outcome than a claim assessed against the house you didn’t tell them you had.
During the works: the gap most homeowners miss
Your own buildings policy usually keeps covering the existing structure while work is under way, but it typically won’t cover the contractor’s liability, tools, or work-in-progress materials — that’s what the trade’s own insurance is for. Ask to see a public liability certificate before signing anything, and check whether your policy has an unoccupied-property clause if you’re moving out during the build.
What to do in the next 30 minutes
Find your current buildings and contents policy documents and check the definition of “notifiable alterations” in the small print.
List every job completed on the property in the last three years, however small, and mark which ones you told your insurer about.
Call or message your insurer about anything currently underway or planned in the next six months.
Ask your contractor for a copy of their public liability insurance certificate and keep it with the job’s paperwork.
Photograph the work at first fix, second fix and completion — useful for a future claim or a sale, not just for the insurer.
Keep the invoice, the disclosure confirmation, and the completion certificate together against the property, rather than scattered across email threads and a kitchen drawer.
Record improvements in Home+ as you go, so the paperwork trail an insurer or a buyer eventually asks for is already sitting against your property record, not being reconstructed from memory two years later.
FAQ
Do I need to tell my insurer about a loft conversion? Yes. A loft conversion changes the structure, the rebuild cost, and often the escape routes, so it should be disclosed before work starts, not on renewal.
What happens if I never tell my insurer and never make a claim? Nothing happens immediately, but the cover you believe you have may not match the cover you actually have. The gap only becomes visible when you need to claim, sell, or remortgage.
Does a kitchen extension count as notifiable? Almost always, because it changes the footprint, the rebuild cost, and usually involves removing a structural wall. Treat any extension as something to disclose.
Will my premium definitely go up if I tell them? Not necessarily. Some works bring no change; others, like adding a flat roof or converting a loft with a single stair, may.
Do I still need to tell them if the work has building control sign-off? Yes. Building control sign-off confirms the work meets building regulations; it does not tell your insurer what changed about the property, and the two processes are unrelated.
Should I tell my mortgage lender too? Often yes, particularly for structural work or an extension — many mortgage conditions require notice of material alterations, separately from your insurer.
