Can you put a granny annexe in your garden without planning permission?

The first route is the main way to have an annexe without a planning application. A mobile home is not a building in planning terms, because it can be moved, so stationing one in the garden is a use of the land. Under the Town and Country Planning Act 1990, a change in how land is used only counts as development if it is a material change. If your parent lives in it as part of your household, planning inspectors have found no material change of use, because no new home has been created. A brick or timber building of the same size, used the same way, needs an application because putting it up is building work.

Under the second route, permitted development lets you put up an outbuilding without applying, but not as a bedroom, as the section on garden rooms explains.

The third route is rooms inside the house. Converting a dining room into a downstairs bedroom, or fitting a shower room on the ground floor, is work that affects only the inside of the house, and planning law does not count it as development. Your parent is living in the family home, so nothing about how the house is used has changed. The guide to living with elderly parents covers the day-to-day side of that arrangement, and a Disabled Facilities Grant can pay towards adaptations such as a level-access shower.

The fourth route is a full planning application for a permanent building, and do you need planning permission for a granny annexe explains the application, the timescales and what happens if you are refused. The granny annexes guide sets out the wider choice between finding, building and adapting, and the Care at home or a care home guide covers the wider decision about where your parent will live and be looked after.

The starting point is section 29 of the Caravan Sites and Control of Development Act 1960. It defines a caravan as any structure designed or adapted for people to live in that can be moved from one place to another, whether towed or carried on a vehicle. Section 13 of the Caravan Sites Act 1968 extends that to twin-unit mobile homes, the kind that arrive in two halves and are bolted together on site, and sets the size limits shown above.

Some annexes sold as "mobile" or "caravan act" lodges look like small bungalows, with pitched roofs and cladding. How it looks does not decide anything. What matters is whether it meets all three tests, and whether it could still be lifted and moved in one piece once it is assembled.

What to ask a supplier before you orderSection titled What%20to%20ask%20a%20supplier%20before%20you%20order

Ask for the external length and width once assembled, and the internal height from the lowest floor to the highest ceiling. Ask how many sections it has and how it would be moved off the site if it ever had to go. Ask how it sits on the ground, because a unit fixed so firmly that it cannot be moved may stop counting as a caravan. Then ask whether the supplier will give you drawings for a lawful development certificate application, because the council will want them.

Other things that still applySection titled Other%20things%20that%20still%20apply

Avoiding a planning application does not mean nothing else applies. Ask the council's building control team what applies to the water, drainage and electricity connections. If the house is listed, or if the mobile home would sit outside the garden that belongs to the house, for example in a paddock or a field next to it, the position changes and you should talk to the council before going further. A site licence is not needed for a caravan used within the grounds of a house for a purpose incidental to living there, under the first schedule of the 1960 Act. Council tax is a separate question: is a granny annexe subject to council tax explains the discounts and exemptions for an annexe a relative lives in.

Modular and prefab granny annexes compares the different kinds of unit on the market and the costs suppliers leave out, and how much it would cost to build a granny annexe puts the mobile home route next to a conversion and a new build.

Councils and planning inspectors look at the relationship between the people in the annexe and the people in the house. Rother District Council's annexe guidance, for example, says permission will be needed where the person in the annexe has no clear ancillary relationship with the main house, and gives a family member living independently, a tenant and a holiday let as examples.

A planning appeal decided in June 2025 shows how this works in practice. An application in Lancashire asked the council for a lawful development certificate for a mobile home in the front garden of a house, with a kitchenette, two bedrooms and a sitting room, to be used by the family living in the house. The council refused, and the Planning Inspectorate allowed the appeal. The inspector found the mobile home had everything needed for day-to-day living, but it would sit close to the house, was not fenced off, and had no separate address, post box, meters, parking, garden or access. Those facts showed it would be used as part of the household in the main house, so there was no material change of use.

The inspector in that appeal added a warning worth remembering. A certificate is granted on the facts as described. If the annexe is later used in a different way, for example let to someone outside the family once a parent has moved on, the council can look at it again and decide that a material change of use has taken place. Letting out a granny annexe covers what to do in that situation.

When care comes into itSection titled When%20care%20comes%20into%20it

A parent who needs help does not stop being part of the household because somebody comes in to help them. Visits from a carer during the day are visits to your parent's home, wherever in the garden that home sits. Care in a granny annexe explains how visits, overnight help and live-in care can work when a parent lives at the bottom of the garden. A carer who lives in the annexe with your parent raises its own questions about rooms and breaks, and a live-in carer in a granny annexe covers them. If your parent is about to move in and you want to know what help near you would look like, you can search for carers near you and compare their rates before the move.

A lawful development certificate is a formal decision from the council that something you plan to do would be lawful without a planning application. GOV.UK's guidance on lawful development certificates says that once a certificate for a proposed use has been granted, anything done in line with it is presumed lawful, unless there is a material change before the work or use begins. The government's permitted development technical guidance recommends the same certificate for anyone who wants to be certain that an outbuilding does not need an application.

For a proposed use or building, the fee is half of what the equivalent planning application would cost. For comparison, a householder planning application in England costs £548 from 1 April 2026, and your council's fee table shows which figure applies to your proposal.

1. 1

   Gather the facts about the unit

   Before you order

   Get the supplier's drawings and specification showing the assembled length, width and internal height, the number of sections and how it is joined and moved.
2. 2

   Draw where it will go

   A site plan

   Show the mobile home within the garden of the house, how close it is to the house, and that it shares the drive and access. Mark out no separate plot.
3. 3

   Describe how it will be used

   In plain words

   Say who will live there, that they are part of your household, and that there will be no separate address, meters, parking or garden. The council can only decide on what you describe, so be precise.
4. 4

   Apply for a certificate of proposed use

   Through the council or the Planning Portal

   Wait for the decision before the unit is delivered.
5. 5

   If it is refused, you can appeal

   To the Planning Inspectorate

   An appeal against a refused certificate goes to the Planning Inspectorate, which can grant the certificate itself, as it did in the Lancashire case.

You can apply online through the Planning Portal, and GOV.UK's council finder gives you the planning department's details if you want to ask a question first.

The government's technical guidance on householder permitted development says that outbuildings under Class E must be for a purpose incidental to the enjoyment of the house. It then says what that does not include: separate self-contained accommodation, or the use of an outbuilding for primary living accommodation such as a bedroom, bathroom or kitchen. The Planning Portal's outbuildings guidance sets out the size limits and says the same about self-contained living accommodation.

So a garden room fitted with a bed, a shower and a kitchen for a parent is not covered by permitted development, even if the building is within every size limit. Building it as a study and moving a parent in later does not change that, because the change in use is what counts.

If your parent will need help with washing, toilet trips at night or getting in and out of bed, a garden room would not be a good place for them anyway. Designing a granny annexe for care needs covers the level access, door widths, wet room and bedroom space that make care possible.

The government's guidance on planning enforcement sets out each of these steps. It says councils have discretion over whether to take action, and that planning law should be enforced in a proportionate way. If a planning officer gets in touch, answer their questions fully and explain how the annexe is used, because a clear account of a parent living as part of the household may settle the matter.

The time limitsSection titled The%20time%20limits

There is a time limit after which the council can no longer take enforcement action. Since 25 April 2024, the limit in England is 10 years for all breaches, under the Levelling-up and Regeneration Act 2023. A shorter four-year limit still applies to building work substantially finished, or a change to use as a single home made, before that date. Waiting out a time limit is not a sensible plan, because a buyer's solicitor will ask about it.

If you get an enforcement noticeSection titled If%20you%20get%20an%20enforcement%20notice

Note the date it takes effect and appeal well before the deadline. GOV.UK's page on appealing an enforcement notice explains how to appeal. A planning consultant or a solicitor who handles planning can help you decide what to do next.