Bringing family together under one roof is a dream for many—especially when caring for elderly parents or planning for the future. The idea of a “granny annexe” is increasingly popular, but the words “no planning permission” can be both tempting and confusing. Here’s what you need to know before you take the plunge.

For a granny annexe to be built under permitted development rights in England, it must meet specific conditions set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1. Here are the key points:

• The annexe must be “ancillary” to the main dwelling—used in connection with, and not as a separate home.

• It must be within the curtilage (the land immediately surrounding) of a single house, not a flat or maisonette.

• The building cannot be forward of the principal elevation facing a highway.

• Maximum height is generally 2.5m for buildings within 2m of a boundary, or up to 4m for a dual-pitched roof further away.

• The total area covered by outbuildings and extensions (including the annexe) must not exceed 50% of the land around the original house.

• No verandas, balconies, or raised platforms higher than 0.3m.

• Not allowed in the grounds of listed buildings, and restrictions apply in conservation areas, national parks, and Areas of Outstanding Natural Beauty.

• The annexe cannot be self-contained accommodation (e.g., with a separate kitchen and entrance) that could be used as an independent dwelling.

Building regulations approval is still required, even if planning permission is not.
If you’re unsure, applying for a Lawful Development Certificate from your local authority can confirm your plans are compliant.

Who Needs a Granny Annexe?

Families often look for annexes to provide care for ageing relatives, help with inheritance tax planning, or simply create flexible living space for grown-up children, carers, or guests. Sometimes, it’s about consolidating two households into one, saving money and building stronger family ties.

Permitted Development: When Is Planning Permission Not Required?

In England, permitted development rights allow certain home improvements and extensions without a full planning application. Some annexes can be built under these rights, but there are strict rules. The annexe must be “ancillary” to the main house—meaning it can’t be a completely separate dwelling. You’ll need to check if your property is in a conservation area, national park, or is a listed building, as these locations often have tighter restrictions.

Even if planning permission isn’t needed, building regulations still apply. These cover safety, insulation, drainage, and more. You may also want to apply for a Lawful Development Certificate from your local council for peace of mind.

Legal Risks and Pitfalls

Building an annexe without proper checks can lead to enforcement action, which might mean having to remove the structure or pay fines. It can also complicate resale, insurance, and council tax—sometimes annexes are given a separate council tax band. If the annexe is used independently, it could be classed as a separate dwelling, triggering more legal and tax issues.

Checklist: What to Look For When Buying a Property for a Granny Annexe

• Is there enough land for an annexe, with suitable access?

• Is the property in a conservation area, national park, or subject to other planning restrictions?

• Are there any restrictive covenants in the title deeds that could prevent building an annexe or using it as living accommodation?

• Does any existing annexe have a lawful development certificate or planning approval?

• Is the annexe truly ancillary, or could it be considered a separate home (which may breach planning or covenant restrictions)?

• Are there outstanding planning or building regulation issues?

• What’s the local council’s attitude to annexes?

• Will the annexe affect inheritance tax planning or council tax?

• Are there any rights of way, easements, or other legal interests affecting the land where the annexe would be built?

• Has the property ever been subject to enforcement action or notices relating to outbuildings or annexes?
  
  

Practical Tips for Success

Speak to your local council before starting any work. Pre-application advice can save headaches later. Talk to neighbours—objections can sometimes derail even permitted development projects. Get professional drawings and certificates, and keep the annexe clearly linked to the main house (shared utilities, no separate postal address, etc.).

Example

The Patel family wanted to future-proof their living arrangements and inheritance planning. With their grandmother’s health declining, they decided to build a granny annexe for her at their home, aiming to consolidate two households and simplify care. They were also mindful of the potential inheritance tax benefits—knowing that if their grandmother gifted her main home to her children and survived seven years, the value could fall outside her estate for IHT purposes.

To avoid planning delays, they carefully checked the permitted development rules, ensuring the annexe was ancillary (no separate kitchen, shared utilities, and direct access to the main house). They reviewed the property’s title deeds for covenants and confirmed there were no restrictions. The family applied for a Lawful Development Certificate, giving them peace of mind that the annexe was lawful.

By acting early, they not only created a comfortable space for their grandmother but also set up their affairs to potentially reduce future inheritance tax, all while staying within the law and keeping family harmony.

Permitted Development Checklist for a Granny Annexe (Class A, England & Wales):

• The property must be a dwellinghouse, not one created by change of use under Classes G, M, MA, N, P, PA, or Q of Part 3.

• The total area of ground covered by buildings (excluding the original house) must not exceed 50% of the curtilage.

• The height of the annexe must not exceed the highest part of the roof of the existing house.

• The eaves of the annexe must not be higher than the eaves of the existing house.

• The annexe must not extend beyond the principal elevation or any side elevation that fronts a highway.

• For single-storey rear extensions:

  • Detached houses: must not extend more than 4m beyond the rear wall (or up to 8m if not on article 2(3) land or SSSI and neighbour consultation is completed).

  • Other houses: must not extend more than 3m beyond the rear wall (or up to 6m with the same conditions as above).

  • Must not exceed 4m in height.

• For multi-storey rear extensions:

  • Must not extend more than 3m beyond the rear wall.

  • Must not be within 7m of any boundary opposite the rear wall.

• If within 2m of a boundary, eaves height must not exceed 3m.

• Side extensions:

  • Must not exceed 4m in height.

  • Must be single storey only.

  • Must not be wider than half the width of the original house.

• No verandas, balconies, or raised platforms.

• No installation or alteration of microwave antenna, chimney, flue, or soil/vent pipe.

• No alterations to any part of the roof.

• The dwellinghouse must not be built under Part 20 (new dwellinghouses).

Additional Notes:

• The annexe must remain ancillary to the main house, not a separate dwelling.

• Building regulations approval is still required.

• Restrictions apply in conservation areas, national parks, and for listed buildings.

Conclusion

A granny annexe can be a wonderful solution, but it’s vital to check the legal angles before you start. Permitted development offers a shortcut, but only if you stay within the rules. Take your time, do your homework, and you’ll be well on your way to creating a safe, comfortable space for your loved ones—without unnecessary drama.