Many people with a long or wide garden wonder whether another house would fit in it, perhaps a bungalow for a parent, a smaller home to downsize into, or a plot to sell.
In many cases you can build a second house in your garden, but it always needs planning permission and not every garden is suitable. Here is what the council will look at, and what to check before you spend money on drawings.
Do I need planning permission for a house in my garden?
Yes. A new, separate home always needs planning permission. Permitted development rights cover sheds, garden rooms and other outbuildings used incidentally to the main house. They do not cover self-contained living accommodation, and no permitted development right allows a new house in a garden.
Most people apply for full planning permission with detailed drawings. Outline permission can establish the principle first, but the details still need approving later.
Because the principle is often the main question, council pre-application advice can be a sensible first step. Our article on pre-application advice explains when it is worth paying for.
Is an annexe different from a separate house?
Yes. An annexe is extra accommodation used as part of the main home, often by a relative. It usually shares the garden, drive and services, and councils often add a condition stopping it being let or sold on its own.
A separate dwelling is an independent house with its own garden, parking and, usually, its own access and services. The council assesses it as new housing under its local plan policies.
A self-contained annexe still normally needs planning permission. If you might sell the new home one day, apply for a separate house from the start.
What will the planners look at?
Local plans vary, but the same issues come up again and again on garden plots.
- Location. Many councils draw a settlement boundary around towns and villages. Inside it, a new house is usually acceptable in principle. Outside it, permission is much harder to get.
- Access. The new house needs a safe way in and out, with good visibility onto the road. A long drive past the existing house can raise noise concerns.
- Parking. Both houses need parking that meets the council’s standards.
- Overlooking. New windows should not look straight into neighbouring gardens or rooms, and the house should not be overbearing or block light.
- Garden size. Both homes need a reasonable garden. Leaving either without usable outdoor space is a common reason for refusal.
- Character. A house tucked behind others, known as backland or tandem development, is resisted in some areas and accepted in others.
A modest bungalow or dormer bungalow is often easier to fit than a two-storey house, because it limits overlooking and sits more quietly behind existing homes.
How will the new house get water, drainage and power?
A separate house needs its own water, electricity and drainage, normally with its own meters. Sharing the existing supplies can cause problems later, particularly if the plot is sold.
Check early whether the new house can drain to a public sewer by gravity, as a pump or private treatment plant adds cost. New connections are charged for, and quotes can take several weeks.
Does it need Building Regulations approval?
Yes. Planning permission and Building Regulations are separate, and a house in a garden needs Building Regulations approval like any other new home.
On a plot set well back from the road, check early that a fire engine can get close enough to the house.
Will I have to pay the Community Infrastructure Levy?
Possibly. Where a council in England or Wales charges the Community Infrastructure Levy (CIL), it normally applies to every new home, whatever its size.
If you will live in the house yourself, you may be able to claim the self-build exemption, and an annexe can qualify for a separate exemption. Both must be claimed, and a commencement notice submitted, before work starts, or the exemption is lost. Our guide to the self-build CIL exemption covers the process.
Does biodiversity net gain apply?
In England, the biodiversity net gain (BNG) rules changed on 6 August 2026. For planning applications made on or after that date, sites of 0.2 hectares or less (about half an acre) are exempt, unless the development affects a priority habitat on the site. Most garden plots are well under that size.
The separate self-build exemption has been removed, so a larger plot may need to show a gain even if you plan to live there. The government’s guidance on BNG exempt developments sets out the detail. Either way, the council may still ask for wildlife surveys if trees, hedges or old buildings are affected.
Can I sell the new house separately?
Yes, if it has permission as a separate dwelling. A solicitor will need to register the new plot as a separate title, and if your home has a mortgage, the lender will normally need to agree to the land being released.
Check your deeds for restrictive covenants that limit building. Splitting the garden can also affect the value of your existing home, so ask a local estate agent before you commit.
What about council tax?
A separate house gets its own council tax band once it is built. A self-contained annexe is often banded separately too, but in England a discount or exemption can apply when it is used as part of the main home or a relative lives there.
What about Scotland, Wales and Northern Ireland?
Planning is devolved, but a new house in your garden needs planning permission everywhere in the UK.
Wales is similar to England: outbuilding permitted development covers incidental uses only. The English BNG rules do not apply, but Planning Policy Wales expects a net benefit for biodiversity, such as new planting or bird and bat boxes.
Scotland also requires planning permission, and you will need a building warrant from the council before work starts. CIL does not apply, and the equivalent of outline permission is called planning permission in principle.
Northern Ireland guidance confirms you need planning permission to build a separate house in your garden. Building control approval comes from your council, there is no CIL, and households pay domestic rates rather than council tax.
Final thoughts
A second house in the garden can work well, but only if the plot can take a modest home without harming the existing house, the neighbours or the street. Look hard at access, parking, garden space and services first.
The simplest starting point is to choose one of our ready-made house designs and have it customised to suit your plot. Our bungalows and dormer bungalows often suit garden plots, and our house plans search lets you filter the range by size and bedrooms. For some of our most popular designs, a Design Feasibility Pack (£29.99) helps you check plot fit, budget and planning points first, and the full £29.99 is credited if you order Planning Application Drawings for any of our designs within 18 months.
If nothing in the range suits, we can design a home for you from scratch. Our Start Here page explains how to get started, or get in touch to talk through your plot.
