When Is An Annexe A Separate Dwelling?

Working out whether a  granny annexe is classed as a separate dwelling might not be the first thing on your mind when you’re exploring or thinking of moving a family member closer to home.

However, it’s an important question to ask yourself, and one that can have a big impact on everything from annexe planning permission, to council tax and insurance.

As the UK’s leading annexe specialist, we can help you find the answers. From your initial planning consultation to the finishing touches on your new home as part of our full turnkey solution, we’re here to make the process clear and stress‑free.

To help you get started, we’ve answered some of the most common annexe questions we receive about the practicalities and separate dwellings status below.

Are granny annexes classed as a separate dwellings?

In most cases, no. The way an annexe is used plays a big role in how it’s classified, and for the vast majority of families building a self‑contained home for an elderly parent or relative, it won’t be treated as a separate dwelling.

As long as the annexe remains genuinely linked to the main house, for example, used by a family member and not rented out independently, it is typically not considered a standalone residence. That means you shouldn’t face the complications associated with separate dwelling status.

Is a detached building automatically classed as a separate dwelling?

The short answer is ‘no’.

Planning guidance focuses on how the building is used, not whether it’s physically connected to your main home. So, whether your annexe is linked to an existing extension, attached to a garage, or completely standalone in the garden, it can still be classed as part of the same dwelling.

To make things simpler, all our granny annexes are designed as a detached structure and under normal circumstances, it will still be considered part of your main residence rather than a separate home.

Does an annexe have its own postal address?

No, it does not. Because an annexe sits on the same plot of land as the main home, it will usually share the same postal address. For many families, this is actually a real advantage, especially when the annexe is used by elderly parents or grandparents.

Sharing an address makes it easier for the wider family to help with day‑to‑day tasks, such as collecting parcels, managing post, or dropping things off when needed. It keeps life simple and convenient for everyone.

Will I need to pay council tax for my annexe?

Council tax is one of the biggest ongoing costs of home ownership, so it’s no surprise that it’s a key concern for families planning a garden annexe.

While the rules can feel complicated, the simple answer is this: annexes are usually given their own council tax band, but you’re unlikely to pay the full amount.

Most local authorities offer a 50% discount when the annexe is occupied by a family member and sits within the grounds of the main home. This means your annexe will be recognised for council tax purposes, but the cost is significantly reduced for families using it to support relatives.

You can find out more in our annexe resource library if you’d like a deeper breakdown of how the council tax discount works.

Will I need to get planning permission for my annexe?

The simple answer is yes. While there are a few rare situations where an annexe can be built without full planning permission, if you’re creating a semi‑permanent home where someone will live, you will almost certainly need to apply to your Local Planning Authority.

Planning can feel complex and overwhelming, but it doesn’t have to be. Our online guide to planning permission for your annexe is a great place to start, or get in touch with one of our experts and let them point you in the right direction.

Having helped more than 500 customers bring their annexe plans to life, we’ve built up a 94% success rate in planning applications. In fact, we’re so confident in our approach that we offer a full money‑back guarantee if your application isn’t approved.

Can I use my garden annexe as a holiday let?

On paper, it might seem straightforward: build an annexe, then list it on Airbnb. But in reality, most garden annexes are designed and given planning permission as residential living spaces for family members, not as commercial holiday accommodation.

With that said, should a family member pass away, or go into full time care, there are ways to change the use permission of the building, and certain limitations that you can stay below to rent out your annexe.

As there are quite a few different factors to consider with this, it is always best to speak with the experts to stay compliant with local regulations.

More questions? Just ask iHus

If you have any other questions or concerns about your annexe plans, or simply would like to talk through your ideas with someone who understands the process inside and out, our annexe specialists are here to help, just contact us today.

You might also want to check out our free library of FAQs, blogs and webinars and explore articles.