Legal Considerations of Building a Granny Annexe

If you’ve got an elderly relative, such as a parent, thinking about their care needs or wondering if they are safe can be worrying. If you don’t live close by, this can make worries worse, knowing that you can’t get to them quickly if you were needed in an emergency. What to do though? With rising care costs making care seem unaffordable, the worries soon mount up and you can find yourself becoming increasingly concerned about the future.

These worries mean many families are turning to building granny annexes in their own back gardens, so that can have relatives living close by but still retaining a bit of independence. It has become an increasingly popular option for families over the past ten years.

So, if building a granny annexe is something you have considered you may well now be thinking about the legal considerations and want you to need to think about before contacting a granny annexe provider. Here are some key points you should consider first.

Planning Permission

A building with planning permission is a disaster waiting to happen – you might get away with it for years before you are suddenly told that the building must come down. That is why it’s important to get planning right, the first time around.

A separate self-contained annexe in your garden is likely to need an application for full planning permission from your Local Planning Authority. This is usually achieved by either a ‘householder application’ or The Caravan Act.

Planning can be a complex matter and thinking about it might even put you off building an annexe. Look for a supplier who includes planning permission as part of your development.

Here at iHUS, our planning permission service is automatically included. Our in-house planning specialist will apply for planning permission and liaise with the relevant authorities on your behalf. You can read more about our planning service here.

Are There Any Other Permissions Needed?

In addition to planning permission, there may be other legal requirements that you need to comply with. It is important to check the title deeds of your home for any clauses.

For example, your title deeds may contain restrictions which mean that any new building work would require the consent of an adjoining landowner or another third party. Although it is likely that you would be aware of this it’s a good idea to double-check.

If your home is leasehold, then it’s highly likely that you will need your landlords’ consent before any work begins. Also, you may need your lender’s consent if your home is still subject to a mortgage.


Building a new granny annexe on your property shouldn’t make you liable for stamp duty land tax in most circumstances. However, if you sell the property in the future, stamp duty land tax will apply and could affect how desirable your property is to potential buyers.

Before starting your building project, you should also consider the potential impact it may have on liability for capital gains and inheritance tax. Tax laws in this area are very complex so it is vital that you speak to a family solicitor and financial advisor before any firm decisions are made.

Annexe Ownership

Consider who will own your annexe. Joint ownership is most common because it seems to be the fairest option – especially if both parties made a financial contribution. You must consider what will happen if the annexe occupant dies – they will be entitled to pass their share of ownership to whoever they like, this will usually be in their will. In all likeliness, you will agree beforehand that the benefactor will be you, but it is worth double-checking what your parent has in mind.

Annexe Finance

Finally, and one of the biggest areas to consider is how you will finance your annexe.

You or your parents might have savings that will finance the build but in a lot of cases, money is usually borrowed to build an annexe.

Whether you borrow the money, or it comes from savings, if finances are being combined between family members then you should all be clear on the financial arrangement and its implications. Again, this is something you should discuss with your family solicitor, who can offer their best advice and produce a written agreement which reflects everyone’s intentions.

iHUS Granny Annexes

for more advice on building a granny annexe and the legal considerations please get in touch.

Click here to view our core range of annexes and download a brochure.

Recent Projects

iHUS Granny Annexe Bath 1


In Autumn 2020 Wendy Hamm and her family approached iHus as they were contemplating an annexe build in their back garden to house Wendy’s mother. Wendy’s mother Jane, 82, was living over an hours drive away from the family. Wendy’s day to day responsibilities meant that visits to Jane were a lot less frequent then they would have wished. Read their story here.
can i build a granny annexe in my garden

Jean Aldridge

Listed building status lead to green oak cladding and Cotswold stone tiles being used to meet strict planning criteria.
Hot tub outside granny annexe

Ingrid & Donna Giles

Ingrid & daughter Donna Giles opted for a custom designed two-bed annex with large outdoor decked area.
Clarke custom granny annexe

Custom Engineered

This large, two-bedroom custom annexe was finished to an exceptionally high specification, with open-plan kitchen and living area.

Download Your Free Annexe Brochure

Simply fill in the form and you will be emailed a link to download our 32 page annexe brochure.

    Simply fill in the form and you will be emailed a link to download our 32 page annexe brochure. Please check your Junk mail if your brochure doesn’t appear in your inbox

    Request A Hard Copy?:

    Download Your Free Annexe Brochure

      Simply fill in the form and you will be emailed a link to download our 32 page annexe brochure. Please check your Junk mail if your brochure doesn’t appear in your inbox

      Request A Hard Copy?:

      Talk to a Consultant

      We know that building an annexe can seem daunting which is why we created our Signature Move process.

      It all starts with a conversation where we want to get to know you better, understand what you need and give you an opportunity to ask any questions you might have.

      To ger started complete the form on the right and we will get in touch.,,

        Simply fill in the form and one of our consultants will get in touch