Planning drawings, budgets, party wall notices and building regulations usually get all the attention. Insurance is often an afterthought.
That matters because standard home insurance, while building an extension, may not cover the same risks once structural work starts. A house that is normally secure can be opened up, scaffolded, filled with materials, or left partly unoccupied. If you are extending your home, check your cover before work begins.
How the Right Insurance Protects You When Building an Extension
An extension changes the risk around your property for a while. Walls may be opened, parts of the roof may come off, and contractors may be on site every day.
That is why building extension insurance matters. The right cover can help protect the existing house, the new works, materials on site, and sometimes contents if they are damaged or moved into storage.
How Does Building an Extension Affect My Home Insurance?
Your insurer may see the property as a higher risk during the works. Structural alterations, scaffolding, skips, regular contractor access, and temporary openings can all affect the cover you already have.
Some insurers will continue your normal policy if they have been told in advance. Others may increase the premium, raise the excess, place restrictions on cover, or ask you to arrange specialist building insurance during extension works instead.
When the extension is complete, the rebuild cost of the property will usually be higher as well. A larger footprint, new glazing, extra bathrooms, or upgraded finishes can all increase the amount it would cost to rebuild the house.
Do I Need to Tell My Insurance Provider About My Extension?
Yes. If the work is structural, tell your insurer before the build starts.
Give them a clear outline of the project, when work begins, the likely contract value, whether you will stay in the house, and who is carrying out the build. Mention anything that changes the risk, such as demolition, hot works, scaffolding, or periods when the house will be empty.
Failing to disclose the work before it starts can cause problems if you later need to make a claim.
Does My Builder’s Insurance Cover the Work?
It helps, but it is not enough on its own. A reputable contractor should usually have public liability insurance, employers’ liability insurance, and often contract works insurance. You should ask for proof before work starts. These policies can help with injury claims, accidental damage caused by the builder, or loss relating to the works and materials.
Even so, your builder’s insurance may not fully protect the existing house, your belongings, or alternative accommodation if you have to move out after a serious incident.
So while builder cover is important, it should sit alongside your own house insurance while building extension works are underway, not replace it.
What Does Home Renovation and Extension Insurance Cover?
This varies by insurer, but specialist cover can include:
- The existing structure of your home
- The extension works in progress
- Materials stored on site
- Contents in the house or temporary storage
- Public liability linked to the project
- Alternative accommodation if the property becomes uninhabitable
- Periods when the home is unoccupied during the build
Poor workmanship, wear and tear, gradual damage, and undeclared works are common gaps.
Will Having an Extension Increase My Home Insurance premium?
Often, yes. During the works, the premium may rise because the property is temporarily exposed to more risk. Once the extension is complete, the premium may rise again because the rebuild value is higher.
The bigger issue is whether the policy still reflects the real value of the property and the work being carried out.
How Else Might an Extension Affect My Home Insurance Policy?
If you move out during the build, your standard home policy may no longer be suitable. If furniture goes into storage, check whether it stays insured away from the property. If the finished project includes features such as large glazed doors or underfloor heating, your insurer may need those details once the work is complete.
It also helps to keep contracts, invoices, proof of your builder’s insurance, and completion paperwork together.
Can I Build My Own Extension?
You can manage or carry out some of the work yourself, but the normal legal and technical rules still apply.
All extensions must comply with building regulations, whether or not they need planning permission. Some may fall within permitted development or require planning permission, depending on the size of the extension, the property type, and the location.
From an insurance point of view, a self-managed build can be more complicated. Your insurer may want more details on who is doing the work and what liability cover is in place.
What About Indemnity Insurance For an Extension Without Building Regulations?
This is separate from building insurance during extension works. Indemnity insurance for an extension without building regulations usually comes up later, often when a property is sold or remortgaged, and the right building control paperwork cannot be found. It is designed to cover certain legal and enforcement risks linked to missing approval.
What it does not do is confirm the work is safe, prove it meets the rules, or pay to correct poor construction. If approval was never obtained, or the final certificate is missing, the proper route may be retrospective approval through regularisation. So indemnity insurance is not a substitute for proper sign-off.
Final Thoughts
Insurance should be part of the extension process from the start. Before work begins, tell your insurer what is planned, ask your builder for proof of cover, and make sure there are no gaps between the existing house and the new works.
Then, once the extension is finished, update your policy so the rebuild value reflects the completed project.
If you are still at the planning stage, it also helps to get clear on planning permission and permitted development and on building regulations for extensions.
If you are planning a home extension and want experienced support from design through to planning and build, Plus Rooms can help. Our team specialises in high-quality extensions across London, managing every stage of the process to keep your project running smoothly. Get in touch today to discuss your ideas and see how we can bring your plans to life.
