How much does a granny annexe cost in the UK?
A granny annexe costs £60,000 on average in the UK. Most jobs fall between £30,000 and £150,000 installed. Annexe type: Garden annexe £30,000 to £60,000; Larger or brick-built annexe £60,000 to £100,000; Attached extension annexe £80,000 to £150,000. Prices reviewed July 2026.
A granny annexe, also called a granny flat, is a self-contained living space with its own kitchen and bathroom, in the garden or attached to the house. Cost depends on size, build type and the fit-out.
Granny annexe cost calculator
Use the calculator to price your granny annexe in 2026. Adjust the options and area for a UK cost range. Nothing is sent anywhere.
Granny annexe cost breakdown
Typical granny annexe costs, by option:
| Annexe type | Typical UK cost |
|---|---|
| Garden annexe (modular, one bed) | £30,000 to £60,000 |
| Larger or brick-built annexe | £60,000 to £100,000 |
| Attached extension annexe | £80,000 to £150,000 |
| + Full kitchen and bathroom fit-out | add £8,000 to £20,000 |
| + Utilities connected to the main house | add £3,000 to £10,000 |
What's included in the price?
Typical granny annexe prices include:
- The structure, insulated for year-round living
- Kitchen and bathroom fit-out
- Electrics, heating and plumbing
- Connection to services
What changes the price?
The things that move granny annexe prices most:
Garden annexe versus an attached extension
Size and number of rooms
Kitchen and bathroom spec
Connecting utilities to the main house
These are why two quotes for the same job can differ, and the only way to know your price is to get prices from local firms (through Bark; we may earn a fee, at no extra cost to you).
Does where you live change the cost?
In London, a granny annexe typically costs around £72,000 installed, about 20% above the UK average of £60,000. In the North, Scotland and Wales the guide figure is nearer £58,000.
| Region | From | Typical | Up to |
|---|---|---|---|
| Midlands / East (UK average) | £30,000 | £60,000 | £150,000 |
| London | £36,000 | £72,000 | £180,000 |
| South East / South West | £31,500 | £63,000 | £157,500 |
| North / Scotland / Wales | £29,000 | £58,000 | £145,500 |
Guide prices installed, scaled with the same regional multipliers as the calculator. Not quotes.
Granny annexe cost in major UK cities
| City | From | Typical | Up to |
|---|---|---|---|
| Belfast | £28,500 | £57,000 | £142,500 |
| Birmingham | £30,000 | £60,000 | £150,000 |
| Bristol | £31,500 | £63,000 | £157,500 |
| Cardiff | £29,000 | £58,000 | £145,500 |
| Edinburgh | £29,000 | £58,000 | £145,500 |
| Glasgow | £29,000 | £58,000 | £145,500 |
| Leeds | £29,000 | £58,000 | £145,500 |
| Liverpool | £29,000 | £58,000 | £145,500 |
| London | £36,000 | £72,000 | £180,000 |
| Manchester | £29,000 | £58,000 | £145,500 |
| Newcastle | £29,000 | £58,000 | £145,500 |
| Sheffield | £29,000 | £58,000 | £145,500 |
City guide estimates, scaled by local labour costs. Indicative averages for granny annexe, not quotes.
In London and the South East, figures run above the national figures, mainly on labour and groundwork.
Compare this with a real quote
The figures above are guide prices. Two or three quotes for your granny annexe tell you what it costs where you live.
Free and no obligation. You answer a few questions on Bark, local pros get in touch, and you decide who, if anyone, to hire. We may earn a fee, at no extra cost to you.Common questions
How much does a granny annexe cost?
A granny annexe costs roughly £30,000 to £150,000 installed in the UK, typically around £60,000. A modular one-bed garden annexe is £30,000 to £60,000, a larger or brick-built annexe £60,000 to £100,000, and an attached extension annexe £80,000 to £150,000. A full kitchen and bathroom fit-out and connecting utilities to the main house add to that.
Do I need planning permission for a granny annexe?
It depends on how it is used. In England, a garden building used for a purpose incidental to the house, such as a garden office, can fall under permitted development, but the government's permitted development guidance says that does not cover primary living accommodation such as a bedroom, bathroom or kitchen, so a garden annexe with any of those usually needs planning permission. One lived in independently, with its own kitchen, bathroom and entrance, counts as a separate dwelling. Always check with your council before building, as getting it wrong can mean an enforcement notice.
Do you pay council tax on a granny annexe?
Often, yes. A self-contained annexe can be banded separately for council tax, though in England there is a 50 per cent reduction where it is the sole or main residence of a relative of whoever pays the council tax on the main house, or where it is used as part of the main home. The relative does not have to be dependent: that is the condition for the separate full exemption, which applies in England and Wales where the relative is aged 65 or over, substantially and permanently disabled, or severely mentally impaired (in Wales, has a significant cognitive impairment). It is worth checking your council's rules, because the treatment varies by situation.
Is a granny annexe a good idea?
For keeping family close while giving everyone independence, an annexe can be well worth the £30,000 to £150,000, and it can add value or rental potential later. The things to weigh are the planning position, the council tax treatment, and whether the layout genuinely gives privacy for both households. Get the planning and council tax questions answered before committing, because they shape the whole project.
Is a granny annexe cheaper than an extension?
A modular garden annexe can undercut a full attached extension for the same floor space, because it is built off-site and needs less groundwork, while an attached or two-storey annexe costs as much as or more than an extension. It also keeps the accommodation separate, which is the point of an annexe. So it depends on whether you want separate, independent space or simply more room joined to the house.
Can I build a granny annexe myself?
If you are a capable builder you can self-build and save on labour, but most people buy a modular garden annexe, from £30,000 to £60,000, because it arrives largely finished. Foundations, drainage and connecting utilities to the main house, around £3,000 to £10,000, plus the kitchen and bathroom fit-out at £8,000 to £20,000, are where the skill and cost sit. Building regulations apply if someone will sleep there, so budget for sign-off.
Does a granny annexe have to pay the Community Infrastructure Levy?
It can, so claim the exemption before work starts. The levy only applies where your council has adopted a charging schedule, and there any development that creates a new dwelling is potentially liable whatever its size, which can include a self-contained annexe. In England, an owner who lives in the main house can claim the residential annex exemption under regulations 42A and 42B of the Community Infrastructure Levy Regulations 2010, and must have it granted and submit a commencement notice before starting on site. Letting the annexe, or selling it separately, within three years of completion withdraws the exemption.
Official guidance and sources
The rules and schemes referenced on this page come from these official UK sources. The price figures are Costwise's own; see how we price.
- Permitted development rights for householders: technical guidance GOV.UK · The government's guidance on the outbuilding rules, including that incidental use excludes primary living accommodation such as a bedroom, bathroom or kitchen, and how eaves height is measured.
- Council Tax (Reductions for Annexes) (England) Regulations 2013 legislation.gov.uk · The 50 per cent council tax reduction in England for an annexe lived in by a relative of the main household, or used as part of the main home.
- Council Tax (Exempt Dwellings) Order 1992 legislation.gov.uk · Class W exempts an annexe that is the home of a dependent relative, defined as aged 65 or over, severely mentally impaired, or substantially and permanently disabled.
- Community Infrastructure Levy GOV.UK · The government's guidance on the levy, including the residential annex exemption, claiming it before work starts, and losing it if the annexe is let or sold within three years.
Cite this data
These figures are free to use in articles, reports and research under a CC BY 4.0 licence. All we ask is a credit to Costwise, and online a link. Where your style allows, please make "Costwise" the linked word so readers can check the figure for their own region.
Costwise (2026): A granny annexe typically costs £60,000 in the UK, ranging from £30,000 to £150,000 installed. Reviewed July 2026. costwiseuk.co.ukSource: Costwise (costwiseuk.co.uk)Costwise (2026). Granny annexe cost. Costwise UK cost data, version 2026-10-05. https://costwiseuk.co.uk/granny-annexe-cost/2026-10-05 (158 jobs)Dataset DOI: 10.5281/zenodo.21159943 · also on Kaggle, Hugging Face and Figshare. Method: how we price. Downloadable CSV.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.