Garden Rooms & Permitted Development Rights
The key factors
Modern standard sized garden rooms don’t usually require planning permission because they fall under class E – Buildings etc of the permitted development rules.
To Stay within the rules
Your garden room must be no more than 2.5m in height**, measured from the bottom of the building to the top of the roof (if it is within 2m of the boundary)
It must not be used for living or sleeping accommodation
It and any other buildings must not take up more than half of your garden area
The maximum area of the garden room is 30sq metres.
You will need to go down the planning route.
If you want to build a larger than average garden room
If you intend to use your garden room as an extra bedroom or guest living space, including Airbnb.