Granny Annexe Design, Layout & Build: FAQs

Size and feasibility

How much space you need, and what’s possible on a typical plot.

How big can a granny annexe be?

An annexe can’t take up more than 50% of your garden or exceed the footprint of your main property. Under the Caravan Act we can build up to 20 metres by 6.8 metres, which comfortably accommodates a one- or two-bedroom home with a kitchen, bathroom and living space. In practice, most gardens have more than enough room — you can see the footprints of each model on our annexe designs page.

Can you build an annexe in a small garden?

Usually, yes. Your garden doesn’t need to be large, as long as there’s room for the annexe without spoiling the garden’s look and usability, plus suitable access. We explain what makes a plot suitable in can I build a granny annexe in my garden?

Can you have a two-bedroom granny annexe?

Yes. We build both one- and two-bedroom annexes — browse the full range on our annexe designs page.

Design, layout and customisation

Your annexe is designed around the people who’ll live in it, down to the finishes.

What’s the best layout for a granny annexe?

It depends on who’ll live there and how. For an older relative, open-plan living with a separate bedroom and a step-free shower room tends to work best, keeping everything on one level and easy to move around. A guest annexe or home office might instead prioritise flexible, multi-use space. With our Classic range we design around your needs rather than fitting you to a fixed plan.

Can a granny annexe be customised?

Our Classic range can be fully customised, or we can design from scratch to your own brief. Our 3632 range offers fixed, contemporary designs for a modern feel but can’t be altered. We don’t build two-storey annexes, and we don’t convert existing buildings.

Can a granny annexe have a full kitchen?

Yes. A full kitchen is included as standard — oven, ceramic hob, extractor, units, worktop and sink — and can be upgraded to suit your taste.

Can a granny annexe be wheelchair accessible?

Yes, and it’s one of the most common requests. We can build in level, step-free access and wider doorways, a wet room with a level-access shower and grab-rail provision, and enough turning space throughout. Because we design from scratch, accessibility is planned in from the start rather than retro-fitted.

Can a granny annexe be designed for future care needs?

Absolutely. Many families future-proof their annexe even if it isn’t needed yet — level thresholds, wider doorways, a wet room and reinforced walls where grab rails might later go — so the space continues to suit a relative comfortably as their needs change over the years.

Can I choose the windows, doors and cladding?

Yes. You choose from a range of finishes, and your consultant brings samples of everything — cladding, decking, flooring and kitchen units — to your site survey so you can see them in place.

Can a granny annexe have a pitched roof?

Yes. A flat EPDM rubber roof comes as standard, with a pitched roof available for an additional cost.

Building your annexe

How your annexe is planned, constructed and connected.

Do I need planning permission?

In most cases, yes — and we handle the entire application for you, with a 94% success rate. For the full detail on planning and the Caravan Act, see can I build a granny annexe in my garden?

Where do iHus build?

We build across England and Wales.

How long does it take to build?

Once your planning application is validated (up to 4 weeks), the planning process takes around 8 weeks, and the build itself a further 8 to 12 weeks depending on the size of your annexe. In total, most projects run to around 5 to 6 months from first enquiry to handover, and we keep you updated at every stage. You can see how each stage works in our four step process.

How is a granny annexe built?

Each annexe is built off site at our facility in Doncaster, then delivered and assembled on your prepared base, which keeps disruption to your garden and home to a minimum. They are fully insulated and finished to residential standards, using the same quality of materials as a permanent home, so they are comfortable to live in all year round. You can read more about how we build in best in class builds.

How is a granny annexe connected to water, drainage and electricity?

Your annexe is connected to the mains services at your main property for water, drainage and electricity, and we handle these connections as part of the installation. We assess the best routing and any groundwork needed when we visit for your site survey.

Is a granny annexe guaranteed?

Yes. Our annexes are built to last and come with a 10-year guarantee, so you have peace of mind long after the build is complete.

Ready to start designing your annexe?

If you already have a design in mind, or you would like help shaping one, we are happy to talk it through. Browse the full range of annexe designs, read our complete guide to building an annexe in the garden, or check what is possible on your plot in can I build a granny annexe in my garden? When you are ready, request a brochure or speak to an expert.