Understanding Ancillary Accommodation And Granny Annexes
Diane Cossie
There is a lot of mis-information and confusion about granny annexes when it comes to planning permission.
In this article we will help you understand why the only way for you to lawfully build a granny annexe in your garden is to fully understand the difference between “incidental” and “ancillary accommodation.”
Granny annexes are classed as ancillary accommodation which means everything you can do in a normal house, such as eating, sleeping, taking a shower, watching television, etc.
With all types of garden buildings currently being described and advertised as granny annexes you may be easily mis-lead into thinking granny annexes are permitted development.
This confusion has led to lots of homeowners being misadvised and subsequently we have seen a rise in enforcement cases.
Read on to find out why granny annexes and ancillary accommodation are the most important aspects of what you are planning to build in your garden if a family member is going to live in it.
So to potentially avoid a very costly mistake or avoid facing enforcement action in the future take a couple of minutes now to get crystal clear on what is classed as incidental & what is classed as ancillary accommodation. This will also greatly improve your chances of gaining permission from your Local Planning Authority.
What is classed as incidental?
If your primary aim is to use a garden studio style building for incidental use it will probably fall under Class E Permitted Development Rights.
Schedule 2 Part 1 Class E of the General Permitted Development Order (GPDO) allows a homeowner to construct an outbuilding within their curtilage without the need for planning permission.
There will still be conditions that will need to be adhered to but the critical word within legislation for this type of building is incidental.
Incidental use is best used to describe any building or enclosure, required for a purpose incidental to the enjoyment of the dwellinghouse


Examples of incidental use
Permitted development rights for Householders Technical Guidance 2019 provides some guidance;
“Examples could include common buildings such as garden sheds, other storage buildings, garages, and garden decking as long as they can be properly be described as having a purpose incidental to the enjoyment of the house.
A purpose incidental to a house would not, however, cover normal residential uses, such as separate self-contained accommodation or the use of an outbuilding for primary living accommodation such as a bedroom, bathroom, or kitchen”.
Other examples might include Home Office, Gym, Art Studio, Yoga Studio, Pool Enclosure, Garage or Storage.
You may even add a shower room to your home gym or toilet in your garden office, as long as it relates to the incidental use of the garden building.
Ancillary Accommodation Contains Primary Facilities
The Permitted development rights for Householders Technical Guidance 2019 makes it clear what incidental is not, which is primary living accommodation such as a bedroom, bathroom and kitchen.
So it’s clear to see the difference between a granny annexe that has primary facilities & all the amenities you would find in a house (ancillary accommodation) and a home gym room, studio, home office etc (incidental).
A granny annexe, that contains primary facilities such as a bedroom, bathroom and a kitchen does not benefit from Class E Permitted Development rights and therefore requires planning permission or a Certificate of Lawfulness issued by your Local Planning Authority.
If you build an incidental building with the intention of converting it to liveable accommodation in the future you will need to apply for change of use from your Local Planning Authority so it makes sense to do things right from the start to avoid potentially costly mistakes further down the line.


You will need the right paperwork in place should you sell up in the future
It can be tempting to think you might be able to “beat the system” or “save money” and opt for building an annexe in your garden without the relevant permission.
However not only do you face possible enforcement action if someone complains (and very few annexes fly through the approval process without neighbours objecting today) but if you decide to sell up and move without the relevant paperwork (ie planning permission or a Certificate of Lawfulness if it is a mobile home style annexe) in place it could jeopardise the value of your property or make it difficult to sell.
Interested In Great Advice About Annexe Living ?
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- Granny annexes are considered ancillary accommodation not incidental and therefore require permission from your LPA.
- Incidental buildings are any building or enclosure, required for a purpose incidental to the enjoyment of the dwellinghouse”
- The Permitted development rights for Householders Technical Guidance 2019 makes it clear what incidental is not, primary living accommodation such as a bedroom, bathroom and kitchen.
- Use our Contact Us Page to email us with your ideal annexe plan & we’ll be happy to advise you on the best way to get started.
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