How Much Space Do You Need for a Granny Annexe?

If you have landed on this page, then you are likely thinking of putting a granny annexe in your back garden but might not know if it’s even a possibility yet. Some people think building separate living accommodation for a relative is only an option for those with acres of land. Or that you would have to have a detached house at least.

However, many models of granny annexe will comfortably fit into a suburban back garden and that is indeed, the space that most iHUS customers are working with. Read on to see what sort of space is needed for a granny annexe and how to check that you have enough room.


Can I Fit a Granny Annexe in My Back Garden?

This question is a little bit like asking ‘how long is a piece of string? ’…

British gardens do vary quite a bit depending on location. For example, inner-city homeowners probably won’t have a garden or may have a small courtyard if they’re lucky. Terraced houses may also have small backyards. Suburban homes typically have bigger gardens as from the 1920s onwards, the benefits of having outdoor space were recognised by house builders.

According to a survey done by estate agent, Foxtons, the average British back garden is 15-metres long – around 50-foot. The width is normally a lot smaller, giving most gardens a long thin appearance. This does limit what structures you can fit in the average sized garden, but it is entirely possible to fit a granny annexe on a typical back garden.

If you are lucky enough to have a big plot of land or a huge garden, then the sky is the limit! (planning permission granted, of course).

How Can I Check That My Garden is Big Enough For a Granny Annexe?

When considering an annexe, start by thinking what sort of spaces the annexe will need to have, for example, will it need two bedrooms, or just one? Once you have thought about the layout that you will need, start to look at models of granny annexe and their measurements. Our core annexe range all have measurements and layout plans to make it easy for you to make a shortlist of the ones you think might fit in your garden, and suit your needs.

When you have chosen an annexe that you like the look of, its time to get the tape measure out!

When it comes to choosing a model and surveying your garden for a granny annexe, you must also take your Local Planning Authority into consideration. You can’t have an annexe that is bigger than the footprint of your main house – an annexe is to be considered ancillary and subordinate to the main house.

If you already have an extension on your home, then a considerable amount of land will already be taken up and its likely that you will not be granted permission to build an annexe.

Not to worry, it is easy to do a quick check to see how likely it is that you will be able to fit an annexe on your garden and if planning permission will be granted.

Using graph paper, plot out the overall size of your house and garden. You can usually find out the measurements of the overall footprint from site location plans or your title deeds. If not, you can measure the footprint yourself.

Now, add onto that the overall footprint of the iHUS annexe you are thinking about having. If less than 50% of the garden areas is left, then the annexe is likely too big, and you may struggle to be granted permission by the Local Planning Authority.

Our core range of annexes comes in several sizes – if your first choice is too big then look at some of our smaller models and repeat the exercise.

image shows a small granny annexe from iHUS

Small Granny Annexes

If you have an average back garden and aren’t too sure if you could have a granny annexe, you will be surprised to find that our core range features some more compact models that are ideal for gardens.

The Cantley, for example, is one of our most popular models for independent relative living. Measuring in under four metres long, it will fit comfortably in the average back garden.

Its bijou size doesn’t mean you have to sacrifice any quality of life either as the floorplan is designed to maximise living space and suit most requirements.

It is even possible to fit a two-bedroom annexe on an average garden. Look at this project to see how a two-bedroom granny annexe can comfortably fit on an average garden.

Most iHUS customers choose a granny annexe from our core range but if you are struggling to find something that you think will work, size wise, then there is always the option of a custom build. A custom granny annexe means that we can work with you to build a home to your exact specifications – ideal for smaller or quirky garden plots.

image of small granny annexe from ihus

Get in Touch

If you still aren’t sure how to measure your garden or if you could realistically fit an annexe on your plot, then please get in touch. Our team will be happy to advise you and we offer free consultations.

Give us a call on 0808 164 1111 or use our contact form to send us a message.


Recent Projects



Samuel Annexe



Margaret & Nicky Wilson

Margaret Wilson and daughter Nicky recently had their custom annexe featured on BBC One. Click to watch the video walk-though.
Shack at the Back


A two-bedroom Cadeby Extra Plus, finished in grey green Marley cedral weatherboard with flat-roof and feature canopy.

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.

    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.

      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