Before you start
Do you need planning permission for a garden annexe?
It is the first question almost everybody asks, and the answer is more settled than the internet suggests. The distinction that matters is not the size of the building. It is whether somebody lives in it.
The short answer
Yes — almost certainly.
A garden room, home office or gym can often go up under permitted development rights. An annexe cannot. Once a building has its own bedroom, kitchen and bathroom it is self-contained living accommodation, and that needs a full householder planning application to your local authority.
That is not a reason to walk away. It is a reason to get it right at the start, when it is a drawing rather than a building.
Why the kitchen and bathroom decide it
Permitted development covers outbuildings that are incidental to the enjoyment of the house — a workshop, a studio, a store. The moment the building can be lived in independently, it stops being incidental and becomes a separate dwelling in planning terms, whatever it is called on the drawing.
This is why a garden room supplier can often tell you no permission is needed and we cannot. We are not being cautious. They are selling a different thing.
Planning permission and building control are two separate things
They get conflated constantly, and you need both.
Planning permission
Asks whether the building should exist at all — its use, siting, size, appearance and effect on neighbours. Decided by your local planning authority.
Building control
Asks whether what you have built is safe and compliant — structure, insulation, fire, ventilation, drainage. Decided by your local authority's building control team or an approved inspector, who inspects during the build and issues the completion certificate at the end.
Building control is deliberately not us. We supply the kit, the drawings and the technical pack; sign-off sits with an independent qualified body, exactly as it does on any house extension. The wall system is specified to be Building Regulations compliant, and your inspector is the one who confirms the finished building is.
Conditions your council may attach
Permission for an annexe is often granted with conditions rather than refused outright. The common ones:
- Occupancy tied to a member of the household in the main house — the reason most people are building it in the first place.
- A restriction on selling or letting the annexe separately from the house.
- A requirement that the annexe remains ancillary to the main dwelling rather than becoming an independent home.
Which of these apply is local, and your planning officer is the person who will tell you. It is worth a conversation with them before an application rather than after a refusal.
The order to do things in
- Talk to your local planning authority early, informally.
- Settle the siting and size — how far from the house, how far from the boundary, where drainage and utilities can reasonably run.
- Submit the householder application with drawings.
- Once permission is granted, book building control and start on site.
- Build, inspect at the stages your inspector sets, and get the completion certificate.
We supply the drawings and the technical pack the application needs. We can also point you toward planning support. The application itself is between you and your council — anyone promising you permission is promising something they do not control.
One thing worth knowing early
Drainage and utility routes need planning before anyone turns a screw. Where the waste runs, and how far it has to travel to get there, is both a planning consideration and the single most site-specific cost in the project. We walk the site with you first for that reason.