Planning Permission for Sheds and Garden Buildings: Size Limits (UK)

Sheds, garden rooms, home offices, summer houses and workshops are all "outbuildings" to a planning officer, and they share one set of rules. Those rules are generous. Most garden buildings need no planning permission at all, but the limits are about height and position rather than floor area, which is where the confusion starts.

What you can build without planning permission

An outbuilding is permitted development in England if all of these apply:

• Single storey, with eaves no higher than 2.5m.
• Overall height: no more than 4m with a dual-pitched roof, 3m with any other roof, and 2.5m if any part is within 2m of a boundary.
• Position: not in front of the principal elevation of the house.
• Coverage: together with all extensions and other outbuildings, no more than half the land around the original house.
• No verandas, balconies or raised platforms over 30cm.
• Use: incidental to the enjoyment of the house. A home office, gym, workshop or store qualifies. Separate living accommodation does not.

Wales has its own version of these rules. The structure is similar but some limits differ, so check the Welsh Government guidance or ask.

The 2m boundary rule in practice

The rule most people hit is the 2.5m height limit within 2m of a boundary. Gardens are narrow, and the obvious place for a garden room is against a fence. At 2.5m overall you can still get a comfortable room with a flat or very shallow roof and a floor that's not raised. Push the building more than 2m from every boundary and the limit rises to 3m or 4m, which allows a pitched roof and a lot more presence.

Where the rules don't apply

• Listed buildings: any outbuilding within the curtilage needs planning permission.
• Designated land (conservation areas, National Parks, AONBs, the Broads): no outbuildings to the side of the house, and a total limit of 10m² for outbuildings more than 20m from the house.
• Flats and maisonettes: no permitted development rights for outbuildings.
• Article 4 directions and removed rights: check your council's planning portal and the original permission for the house.

Building regulations

Separate from planning, and simpler:

Floor area	Building regulations
Under 15m², no sleeping accommodation	Exempt
15m² to 30m², no sleeping accommodation	Exempt if at least 1m from any boundary, or built substantially of non-combustible materials
Over 30m², or any sleeping accommodation	Full approval required

Electrics in any garden building should be installed and certified by a competent electrician regardless.

A home office in the garden

This is now the most common outbuilding we're asked about. It's fine under permitted development as long as it stays incidental to the house: you working from it is incidental, customers visiting it or staff working there is not. Keep it within the height limits, insulate it properly whether or not building regulations require it, and run power through a certified supply. If it's going to be used all year, the comfort difference between a cheap kit and a properly insulated build is enormous.

Check before you build

The planning checker covers garden buildings, and the local authority finder tells you who to ask if your plot is on designated land. If what you really want is a room that's part of the house, our guide on converting a garage into a room is often the better value route.