If you make changes to your home and don't let your insurance company know, your home insurance policy may become invalid. This means you may not be protected from things like fire, theft, water damage and so on.
It often comes down to the extent of the building work. While smaller, cosmetic tweaks to your home are unlikely to affect your cover, most insurers will want to know about larger projects and whether you're taking it on yourself or leaving it to the professionals.
Each insurer will have a different policy. For example, if you're adding a new bathroom, en suite or wet room, some insurers would need to be told because the number of bathrooms in your home is used to help calculate your premium. that may not be the case for all insurers, but it's always best to make sure by telling them about your plans.
Any work you carry out on your property has the potential to increase the value of your home and, therefore, the cost to rebuild it if it's damaged beyond repair. The higher the rebuild cost, the bigger the risk for insurers, which will need to be reflected in your premium.
Even if you're only spending money on your home to make it a nicer place to live – as opposed to making it a more attractive proposition if you sell – this could still increase the rebuild cost.
Insurers also need to know whether you'll have to move out of the property while work is being carried out. Most providers will insure an unoccupied home for up to 30 days as standard, but longer periods may need additional cover.