An annexe is a self-contained living space next to or connected to the main house. It contains everything needed for independent living, including at least one bedroom, a kitchen, and a bathroom. It also must share the same address of the house it’s a part of. 

Importantly, an annexe is considered ‘ancillary’ to the main home, which means it serves a functional link to your main house, such as supporting relatives needing independent accommodation. 

There’s many types of annexe with lots of different uses. You could rent it out on AirBnB for some extra income (an increasingly popular trend in Kent and Sussex!), or use it to provide future security as families plan for elderly relatives and ‘boomerang’ children who return to live at home whilst saving up.

At The Garden House Company, we build bespoke garden annexes in Kent and Sussex to suit all these needs.

Bi-fold doors pulled back to allow for relaxation on the deck.

Interior of our garden annex

Annexe vs garden room: What’s the difference?

A garden annexe and a garden room are both spaces for your family and friends to enjoy, however, typically a garden room is not used for accommodation or living space. 

A garden room provides additional space to your main house for entertaining, as an office, or simply a place to relax and unwind on a summer afternoon. Learn more about the benefits of a garden room and how we build our garden rooms at The Garden House Company. An annexe can be used for the same purposes, but also contains the essential spaces to make a home.

The difference is subtle but can be important when it comes to tax and planning permission.

When is an annexe a separate dwelling in the UK?

In the UK, the line between an annexe and a separate dwelling can be blurred.

As we’ve covered, an annexe is a self-contained living space with everything needed to call it a home, but is considered ‘ancillary’ to the main home, meaning it should serve a specific purpose that the main house doesn’t. 

If your annexe has its own full amenities (water, heating) not shared with the main home and has a separate entrance, councils in Kent & Sussex may consider it a separate dwelling.

Separate dwellings often sit in higher council tax bands, but in some cases, annexes can claim a reduction.

Is an annexe liable for council tax?

Councils in the UK, including Kent & Sussex, may consider an annexe eligible for its own council tax if it can be classed as a self-contained unit – i.e. it has its own kitchen, bathroom and bedroom. This is true even if it shares other amenities (water, heating) and entrances with the main house. 

However, you might not have to pay any council tax if your annexe will be used by a dependent relative as their main home, a full-time student, or a relative under the age of 18.

Dependent relatives include those over the age of 65, disabled, or who are mentally impaired.

Can I build an annexe without planning permission?

In one of our previous blog posts, we provided a guide to garden room planning permission in the UK. One of the key reasons for needing planning permission was if it would be used for living accommodation.

With that in mind, if you are considering building an annexe, you will almost certainly need planning permission in the UK. You also cannot rent out or sell an annexe without planning permission.

Uses of an annexe

Children

Whilst annexes are most popular for elderly family members, they’re also becoming increasingly used as temporary accommodation for children saving up for their own property, back from university, or simply in-between flats.

My own annexe has been used across all family members! Currently my daughter and her boyfriend are living there after their landlord sold their flat in London and they needed a short-term home whilst searching for their next place back in the city.

They’ve found this ideal during a time of change as they didn’t have to worry (too much) about rent, could spend time around family, and it gives them the flexibility needed to navigate the London rental market.

Holiday let

Alternatively, if you’re looking at an annexe as a potential source of income, you could rent it out on a short-term let or on a platform like AirBnB. Just remember, you’ll probably need planning permissions to do so.

Extra considerations also include letting your mortgage lender know so they can decide if a different mortgage needs to be offered, as well as your home insurance provider, as holiday letting comes with its fair share of potential damages.

Holiday letting in Kent & Sussex is increasingly popular if you do decide to go down this route. The pandemic plus rising cost of living means more and more people are seeking the south of England for a countryside retreat. We’ll certainly be renting our annexe out on Airbnb once we get rid of the kids!

Bi-fold doors open on Garden Annex with double car port created using the roofline from the structure itself.

Exterior of our garden annex

Value of an annexe vs a garden room

Clearly, the value of an annexe depends on what you use it for. Using it as another income stream will raise the value of your home but comes with its share of costs in planning permission and taxation. 

When it comes time to sell your house, an annexe can make your home more attractive to potential buyers – with more adults living longer with their parents, homes which offer greater versatility will stand out in the market. 

So what’s the value of an annexe vs garden room? It’s estimated you could add 20-30% to the value of your property with an annexe, whilst our previous blog post identified an average increase of 8.4% for a garden room. 

It’s not all about money, though. Building an annexe can take more time, investment and potential planning headaches without the right building partner. A garden room offers a simpler, tax-friendly option for extra leisure or work space – read more about how investing in a garden room can add value to your home.

Annexe vs garden room: Your decision

Deciding between an annexe and a garden room depends on your specific needs and long-term plans. An annexe offers a versatile living space that can accommodate elderly relatives, returning children, or generate rental income, significantly increasing your property’s value. However, it requires planning permission and may incur additional council tax. 

In contrast, a garden room provides a simpler, tax-friendly option for extra leisure or work space without the complexities of full living accommodations. 

Ultimately, understanding how you want to use your extra space and your future goals will help you decide which option to go for. At the Garden House Company, we’re experienced in both builds and can guide you on the best design for your needs.

FAQs

A lodger is defined as someone who lives in the property at the same time as the landlord. A lodger can live in an annexe as long as they share a kitchen with the landlord and the landlord has regular access to the annexe area. If the annexe has its own kitchen and is separated from the main part of the house, then you’re considered a tenant, not a lodger, and the annexe will need planning permission.

An annexe is generally considered to be a separate self-contained living space close to the main home, whereas a flat is usually just an extension of the main home.

As an annexe is usually built on the same plot of land as the main home, it does not have its own address.

Traditionally, it’s called a ‘granny’ annexe because they are used to provide accommodation for elderly relatives who want to live independently but still be close to their family. 

However, the use of annexes has now grown to serve adult children needing temporary living space or as short-term holiday lets.

An annexe is considered ‘ancillary’ to the main house, meaning it must share amenities and provide an extra function to the main property, As such, it cannot be sold separately.