Getting planning permission for an annexe for a relative
Most annexes for a relative need planning permission, and the decision turns on whether the council sees ancillary accommodation or a second dwelling. Here is how that judgement is made and how to shape your application around it.
Granny annexe planning permission usually hinges on one question: is the annexe part of your existing house in planning terms, or is it a second, separate home in your garden? An annexe that remains ancillary to the main dwelling is normally acceptable in principle, often with a condition tying its occupation to the house. One that reads as a self-contained independent dwelling is judged against the policies for new housing, which in a back garden, the Green Belt or open countryside is where most refusals come from.
Annexes are rarely permitted development. Extending the house under the General Permitted Development Order 2015 Schedule 2 Part 1 Class A can produce annexe accommodation, but creating a separate planning unit is a material change of use and needs permission under the Town and Country Planning Act 1990 section 55. A detached garden annexe with a bedroom and kitchen is not incidental to the enjoyment of the house, so Class E rarely covers it either.
Ancillary annexe or separate dwelling: the test that decides everything
The courts have approached the meaning of a dwellinghouse by asking whether a building provides the facilities for day-to-day private domestic existence for a household living independently. Applied to annexes, the practical question becomes whether the occupant would be functionally part of your household, sharing the site, the access, the garden and some of the daily arrangements, or living a wholly separate life next door.
That is a matter of fact and degree, which is why two apparently similar schemes can get different answers from the same authority. Officers look at the physical relationship between the annexe and the house, the degree of self-containment, the layout of the plot and the practical reality of how the two will be used.
| Points towards ancillary | Points towards a separate dwelling |
|---|---|
| Attached to the house, or a short distance away within the same garden | Sited at the bottom of a long garden, screened from the house |
| Shares the driveway, bin storage and garden with the host dwelling | Own gated access, own parking bay, own private curtilage |
| Modest floor area relative to the house, one bedroom | Two or more bedrooms, generous living space, utility room |
| Kitchenette or basic food preparation area | Full kitchen with the fittings of an independent home |
| No physical or visual subdivision of the plot | Fence, hedge or wall dividing off the annexe's land |
| Applied for as ancillary accommodation for a named family member | Marketed or described as a self-contained unit or holiday let |
No single row is decisive. A full kitchen alone will not sink an application if everything else says ancillary, and an attached annexe with its own fenced garden and separate entrance from the street can still be refused as a de facto second dwelling.
Why councils tie the annexe to the main house
If permission is granted for ancillary accommodation, expect a condition restricting occupation to the main house. The wording varies, and it is worth reading carefully before you accept it.
Some authorities restrict occupation to a person who is a member of the household of the occupier of the host dwelling, or a dependent relative. Others simply require that the annexe is used only for purposes ancillary to the main dwelling and is not occupied as a separate dwelling. Others add that the annexe must not be sold or let separately, and that on the accommodation no longer being needed the kitchen must be removed or the annexe reintegrated.
The condition protects the council's housing policy, not you. It matters because it affects resale, mortgageability and what happens when the relative no longer needs the annexe. If a condition is drafted so tightly that it would be unusable in five years' time, negotiate the wording with the case officer before determination rather than applying later under section 73 to vary it.
A condition tie is also the reason officers sometimes prefer a slightly less self-contained scheme. It is easier to defend a condition on a building that could not readily function as an independent home.
Design choices that push you into "new dwelling" judgement
The cheapest way to avoid a refusal is to design out the features that make the annexe look like a house of its own.
Keep a physical link where you can. A short glazed connection, a shared lobby or an internal door from the annexe into the host dwelling gives the officer something concrete to point to. Interlocking use, such as a shared utility room or plant room, helps for the same reason.
Hold the plot together. Do not fence off a private garden for the annexe, do not create a second dropped kerb, and keep the parking arrangement shared. Once the plot has been visually subdivided, a future application to sever the annexe becomes much easier to argue, and councils know it.
Be proportionate. An annexe that approaches the floor area of the original house invites the conclusion that it is a dwelling in its own right, and in the Green Belt it also runs into the disproportionate additions test. Where the site is in a conservation area or the building is listed, the annexe's design, materials and impact on the setting will carry as much weight as the use question.
And be straight about the kitchen. Pretending an annexe with a full kitchen has none, then installing it after the decision, is a route to enforcement rather than a clever tactic.
Illustrative example
Illustrative only. A 1930s semi with a 30m garden. The owners propose a single-storey rear and side extension of about 34m2 containing a bedroom, a wet room, a sitting area and a kitchenette, connected to the house through the existing dining room with a lockable internal door. No fence is added, the driveway is unchanged, and the application describes the accommodation as for the applicant's mother. The submission includes a short Planning Statement explaining the ancillary relationship and offering an occupancy condition. That is a straightforward householder application. Move the same accommodation into a detached 34m2 building at the end of the garden, add a full kitchen, a fence and a second parking space, and the same council is likely to assess it as a new dwelling in a back garden.
Turning an existing outbuilding into an annexe
Converting a garage, stable or garden studio into annexe accommodation is a change of use, not building work in the planning sense, so the fact the building already exists does not remove the need for permission. If the building was originally permitted or built under Class E as incidental to the house, sleeping accommodation for a relative goes beyond incidental use.
Rural conversions have a different route. Schedule 2 Part 3 Class Q of the GPDO 2015 allows prior approval for the change of use of an agricultural building to a dwellinghouse, subject to conditions on prior agricultural use, floorspace, unit numbers and the extent of works. That produces a full separate dwelling rather than an annexe, and the tests are technical, so read the current text of Class Q before assuming it applies.
Where works have already happened, a certificate of lawful use under section 191 or 192 of the Town and Country Planning Act 1990 is the only formal way to establish that the use is lawful. A council tax bill is not proof of planning lawfulness.
Council tax, CIL and the exemption worth claiming
Self-contained annexes are commonly banded separately for council tax, and a discount can apply where the annexe is occupied by a relative or is unoccupied and unable to be let separately because of a planning restriction. Check the position with your billing authority.
A separate council tax band does not by itself create a separate planning unit, but it is evidence a planning officer or enforcement officer may look at alongside everything else. Keep the planning description and the way you actually use the annexe consistent.
On the Community Infrastructure Levy, the CIL Regulations 2010 as amended include a residential annexe exemption alongside the self-build exemption. It has to be claimed on the correct form, granted in writing, and the assumption of liability and commencement notice submitted before you start work. Miss that sequence and the exemption is lost even if you qualified. Rates and forms change, so use the current CIL guidance and your council's charging schedule.
What to submit, and what the case officer reads first
An annexe attached to a house is normally a householder application. A detached annexe assessed as a new dwelling becomes a full application with a higher fee and, in most areas, additional requirements. Fees are set nationally and indexed annually, so check the current schedule before you pay.
- Application forms and the ownership certificate, submitted through the Planning Portal or your council's own system.
- A location plan at 1:1250 with the site edged red, and a block plan at 1:500 showing the whole plot, parking and boundaries.
- Existing and proposed floor plans and elevations at 1:50 or 1:100, with the internal connection to the host dwelling shown clearly.
- A short Planning Statement explaining the family need, the ancillary relationship and the occupancy condition you are willing to accept.
- A Design and Access Statement where one is required, for example listed building consent or certain development in a designated area, or where the design case needs explaining.
- Anything on your council's local validation list: tree information where there is a Tree Preservation Order or trees close to the works, a flood risk note in Flood Zone 2 or 3, or a heritage statement in a conservation area.
Officers read the description of development and the block plan first. If the description says "self-contained annexe" and the block plan shows a fenced-off unit with its own access, the assessment has already started badly. If you are unsure which supporting documents your project needs, the full report index sets out the 66 report types by category.
If it is refused
Read the reasons. A refusal on the principle of a new dwelling is a different problem from a refusal on scale, overlooking or design, and it needs a different response.
The usual fallback is to resubmit with the self-containment reduced: connect the annexe to the house, downgrade the kitchen, remove the fence, share the parking, and offer a tightly drafted occupancy condition. Free-go resubmissions are available in many cases within 12 months on the same site, subject to the fee regulations.
Otherwise, appeal to the Planning Inspectorate. Householder appeals run on a shortened timetable, with a 12-week deadline from the date on the decision notice, against six months for most other appeals. Appeal decisions on annexes are indicative of how inspectors weigh self-containment and family need, not binding precedent, so use them to frame an argument rather than to predict an outcome.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter your postcode on PlanScope to see which reports your annexe application is likely to need.
Frequently asked questions
Do I need planning permission for a granny annexe?
Almost always, yes. Extending your house may fall under permitted development, but creating accommodation that functions as a separate planning unit is a material change of use under section 55 of the Town and Country Planning Act 1990. A detached annexe with a bedroom and kitchen is not incidental to the enjoyment of the house, so it is not covered by Class E outbuilding rights either.
What is the difference between an ancillary annexe and a self-contained dwelling?
An ancillary annexe is used as part of your household: shared access, shared garden, modest size, close physical relationship to the main house. A separate dwelling provides everything needed for independent day-to-day domestic life on its own plot. Councils assess it as a matter of fact and degree, looking at siting, self-containment, size and how the plot is divided.
Can the council make me remove the annexe kitchen later?
Some occupancy conditions require the annexe to be reintegrated or the kitchen removed once the ancillary need ends. Read the draft condition before the decision is issued and negotiate the wording with the case officer if it would be unworkable. Varying a condition afterwards means an application under section 73, with no certainty of success.
Will an annexe be charged separate council tax?
Self-contained annexes are often banded separately by the billing authority. A discount can apply where a relative occupies the annexe, or where it cannot be let separately because of a planning restriction. Check with your council. A separate band does not make the annexe a lawful separate dwelling in planning terms.
Is an annexe liable for the Community Infrastructure Levy?
It can be, depending on your council's charging schedule and the floorspace created. The CIL Regulations 2010 as amended include a residential annexe exemption, but it must be claimed and granted in writing, with assumption of liability and a commencement notice submitted before work starts. Miss the sequence and the exemption is lost.
How long do I have to appeal an annexe refusal?
Householder appeals must be lodged within 12 weeks of the date on the decision notice, which is shorter than the six months allowed for most other planning appeals. Many applicants instead resubmit a revised scheme with reduced self-containment, which can often be done free of charge within 12 months on the same site.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.