Demolishing a garden shed or other small outbuilding is normally exempted development and does not require planning permission, provided the shed was itself lawfully built and there is no protected structure or conservation area constraint involved. If there is doubt about the status of the structure or the site, the local authority can confirm the position or issue a formal Section 5 declaration.
Removing a garden shed or similar small domestic outbuilding is generally considered minor, low-impact work and is not something local authorities expect to be notified about, because it does not usually meet the threshold of significant development that planning control is designed to manage. This aligns with the broader treatment of small ancillary structures under the Planning and Development Regulations 2001 (as amended), which exempts many minor domestic works around a house.
The main exceptions arise where the property is a protected structure or lies within an Architectural Conservation Area, in which case even the removal of what looks like a minor structure can be treated more cautiously if it affects the character or setting of the protected building. Demolition of a shed that was itself built without permission, or that is subject to specific planning conditions, may also need to be considered on its own facts.
In the ordinary case of a modern garden shed being taken down for replacement, storage clearance, or landscaping, no planning application is typically needed, but if you are uncertain, particularly on a period property or in a sensitive location, a quick check with the local authority's planning section avoids any risk of enforcement issues later.