Garden studio vs granny annexe: what's the difference and do you need planning permission?
These two terms get used interchangeably online — but the planning rules that apply to each are completely different, and getting it wrong can be costly.
By Distinct Spaces · Updated June 2026 · 6 min read
If you've been searching for a "fully fitted granny annexe" or a "granny pod" for your garden, you've probably noticed that what's being sold varies enormously — from a simple insulated cabin to a fully self-contained one-bedroom unit with its own kitchen, bathroom and separate entrance.
The structure might look similar. But how it's used, and what planning rules apply, are very different things. Here's what you need to know before you start.
The key distinction: ancillary use vs independent dwelling
Planning law doesn't care much about what a building looks like. What it cares about is how the building is used — and specifically, whether it's ancillary to the main house or an independent dwelling in its own right.
Ancillary use means the building is used in connection with the main house: a home office, a gym, a games room, a studio, a hobby space. The people using it live in the main house.
Independent dwelling means the building functions as a separate home — with its own bedroom, kitchen, bathroom and entrance, occupied by someone who lives there independently of the main household.
This distinction determines everything about what you can build, how, and whether you need planning permission.
Garden studios: typically permitted development
A garden studio used as a home office, gym, art studio or similar falls under Class E of permitted development rights — meaning you can build it without a full planning application, as long as it meets certain criteria:
Size and position rules for permitted development:
- Maximum height of 2.5m if within 2m of a boundary; up to 4m with a dual-pitched roof otherwise
- Must be in the garden (not forward of the principal elevation)
- Cannot cover more than 50% of the total garden area (including any other outbuildings)
- Not permitted on listed buildings or in some conservation areas without prior approval
- Must not be used as a separate dwelling
Permitted development does not require planning permission, but building regulations may still apply — particularly if the studio is larger than 15m², has sleeping accommodation, or is closer than 1m to a boundary. A good contractor will check all of this before quoting.
Granny annexes: almost always need planning permission
If the structure is intended as a self-contained living space — a bedroom, a kitchen, a bathroom, used by someone living there independently — it is considered a separate dwelling under planning law. This is true even if the building dimensions would otherwise fall within permitted development limits.
A full planning application is required. This involves the local planning authority assessing the proposal against local planning policy, which varies by borough. Some boroughs in South West London — particularly those with tight housing policies or conservation area designations — are cautious about approving new independent dwellings in gardens.
Planning permission for a garden annexe is not guaranteed. It takes time (typically 8–12 weeks for a decision), costs money in fees, and may be refused or require significant amendments.
The grey area: the "fully fitted" studio
This is where it gets complicated — and where a lot of the online advertising for "fully fitted granny annexes" operates.
A studio with a bed, a kitchenette and a shower room, used by your elderly parent who spends most of their time in the main house, is in a grey area. Planning authorities generally accept occasional sleeping and basic facilities as ancillary use. But a studio that functions as a full-time independent home — even for a family member — moves into self-contained dwelling territory, and the use of the building can be enforced against.
The risk of building a self-contained annexe under permitted development rules (i.e. without planning permission) is that the local authority can issue an enforcement notice requiring you to cease the residential use or even remove the structure. This is uncommon but it does happen, particularly after neighbour complaints.
What we build — and how we advise
At Distinct Spaces, we build insulated garden studios designed for year-round use as home offices, gyms, and ancillary living spaces. Every project starts with a permitted development check for your specific property before we quote — because the rules vary depending on your garden size, previous outbuildings, conservation area status, and whether your property is listed.
If you want a space with sleeping accommodation, a kitchen and a bathroom, we will be straight with you about what's permitted development, what requires a planning application, and what the likely outcome in your specific borough is. We don't build first and answer planning questions later.
The practical question: what do you actually need?
Most homeowners we speak to in Twickenham, Richmond and Kingston want one of three things:
A proper home office — dedicated, insulated, wired for ethernet, quiet and separated from the house. This is straightforward permitted development in most gardens. Timeline: 6–8 weeks from survey to handover.
A guest room — somewhere for family to stay occasionally, with a sofa bed or pull-out. Also generally acceptable as ancillary use, particularly without a permanent kitchen. A grey area worth discussing before building.
A full self-contained annexe — for an elderly parent or a family member who will live there permanently. This is a separate dwelling and requires full planning permission. We can advise on the likelihood of success for your specific property and borough.
Ready to talk through your project? We do free site visits across South West London.
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