Do You Need Planning Permission for a Granny Annexe in the UK?
At a glance
Do most annexes need planning permission?
No. Most are covered by a Lawful Development Certificate.
What is an LDC?
An official council document confirming your annexe is legal.
Who handles the LDC application?
Garden Annexes. 100% success rate. Included in the price.
Next step
Free site survey and fixed all-in price. No obligation.
In most cases, no. The majority of garden annexes installed across the UK do not require full planning permission. Instead, they are covered by a Lawful Development Certificate, which is a simpler, faster and more straightforward process. Garden Annexes handles the entire application on your behalf as part of the turn-key price.
Planning Permission vs a Lawful Development Certificate
There is often confusion between planning permission and a Lawful Development Certificate (LDC). They are two very different things and it is important to understand the distinction.
Full planning permission is required when you want to build something that falls outside what is allowed under Permitted Development rights. It involves submitting plans to the council, a public consultation period and a formal decision that can take months.
A Lawful Development Certificate is a formal document from your local council that confirms your proposed annexe is lawful. It does not go through a public consultation. It is sometimes processed faster and we have a much higher success rate. Most Garden Annexes projects use this route.
Garden Annexes manages the entire Lawful Development Certificate application on your behalf, from preparing the documents to submitting to the council and chasing for a decision. It is included in the turn-key price and our team has a 94% success rate.
When Does a Granny Annexe Need Full Planning Permission?
There are specific circumstances where full planning permission would be required rather than an LDC. These include:
The annexe cannot be proved to be demonstrably moveable. Whilst all Garden Annexes that we produce are considered to be moveable (it’s designed into the structure of each annexe), not every granny annexe provider can demonstrate proper moveability and in many of those cases planning permission will eed to be sought
The annexe is intended to be rented out to someone unconnected to the main household. Renting to a third party changes the planning status of the annexe. Full planning permission would be required before doing so.
The annexe would exceed size limits. There are specific rules about the maximum size of outbuildings relative to the main house and garden. Garden Annexes will advise on this during the design stage.
If any of the above apply to your situation, it does not necessarily mean you cannot build an annexe. It simply means the route to approval is different. Garden Annexes will advise on the right approach for your specific property and circumstances.
What Are Permitted Development Rights?
Permitted Development rights are a set of rules that allow certain types of building work to go ahead without the need for full planning permission. They are granted by the government and apply to most residential properties in England. The do NOT cover residential annexes.
Under Permitted Development, you can build an outbuilding - for example a small garden room - within the grounds of your home without planning permission, provided it meets certain criteria. The key conditions are:
The garden room must not be built forward of the principal elevation of the house.
The garden room must not take up more than 50% of the total area of land around the original house.
The maximum external height must not exceed 2.5m.
What Is a Lawful Development Certificate and Do You Need One?
A Lawful Development Certificate is an official document from your local planning authority that confirms your proposed annexe is lawful. It is strongly recommended.
Without one, you have no formal confirmation from the council that your annexe is legal. This can cause problems if you come to sell the property, remortgage or if a neighbour raises a complaint. An LDC removes all of that uncertainty.
Garden Annexes includes the LDC application as part of every turn-key project. The team prepares all the required documents, submits to your local council and manages the process from start to finish. You do not need to deal with the council directly at any point.
How Long Does the Planning Process Take?
A Lawful Development Certificate application typically takes eight to twelve weeks to be processed by the local authority. Garden Annexes submits the application early in the project timeline so it runs alongside the design and manufacturing stages. By the time your annexe is ready to install, the certificate is usually already in place.
Full planning permission takes longer, typically three to six months, and involves additional preparation. If your project requires this route, Garden Annexes will factor the timeline into the project plan from the outset.
Does a Granny Annexe Affect Council Tax?
When a granny annexe is used by a family member and remains connected to the main household, your local authority should not separately list the annexe. In most cases there is no additional council tax to pay.
If the annexe is rented out to someone unconnected to the household, it may be given its own council tax band. This is one of the key reasons why the distinction between a family annexe and a separately occupied dwelling matters from a planning perspective.
For a full explanation of how planning status affects council tax and other legal considerations, see our guide on when a granny annexe becomes a separate dwelling.
What Happens During a Site Survey?
A free site survey from Garden Annexes is the first practical step toward your annexe. During the visit, the team will:
Measure your garden and assess the available space.
Confirm whether your proposed annexe falls within Permitted Development.
Identify the best position for the annexe on your plot.
Assess the access route for the delivery and installation team.
Provide a complete, fixed all-in price with no hidden extras.
The site survey is completely free and carries no obligation. You can view full pricing across all ranges and sizes before you book, or request the free 2026 brochure which includes every size, range and price in one place.
Frequently Asked Questions
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In most cases, no. Most granny annexes are installed under Permitted Development rights and require a Lawful Development Certificate rather than full planning permission. Garden Annexes manages the LDC application on your behalf with a 96% success rate as part of the turn-key price.
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A Lawful Development Certificate is an official document from your local planning authority confirming that your proposed annexe is lawful under Permitted Development rules. It is not planning permission but it gives you formal confirmation that the annexe is legal, which is important when selling or remortgaging the property.
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Full planning permission is required if the annexe will be rented to someone outside the household, if the property is in a conservation area or National Park, if the annexe exceeds Permitted Development size limits, or if Permitted Development rights have been removed from the property. Garden Annexes will advise on the right route for your specific situation.
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Typically eight to twelve weeks. Garden Annexes submits the application early in the project so it runs alongside the design and manufacturing stages and is usually in place before installation begins.
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Yes. Garden Annexes manages the entire Lawful Development Certificate application from preparing the documents to submitting to the council and chasing for a decision. It is included in the turn-key price and the team has a 96% success rate on applications.
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In most cases no, provided the annexe falls within Permitted Development guidelines. The key conditions are that it must not exceed size limits, must not be rented independently and must sit within the curtilage of the main home. Garden Annexes confirms all of this during the free site survey before any work begins.
Planning Permission for a Granny Annexe
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