Outbuilding Planning Permission Rules

An outbuilding is permitted development if it meets all of the following conditions:

• It is within the curtilage (garden) of the dwellinghouse
• It is not forward of the principal elevation
• It is for a purpose incidental to the enjoyment of the dwellinghouse (garden office, gym, hobby room, storage, etc.)
• It meets the height limits for its location
• The total area of buildings (excluding the original house) does not exceed 50% of the curtilage

The 2m boundary rule is the most common constraint for garden offices and larger sheds. If you want a building higher than 2.5m, it must be positioned more than 2m from every boundary.

The total area of ground covered by all buildings within the curtilage (excluding the original house itself) must not exceed 50% of the total curtilage area.

This includes existing extensions, sheds, garages, greenhouses, and the proposed outbuilding. On smaller plots, this limit can be the binding constraint rather than height.

Class E requires that the outbuilding is for a purpose incidental to the enjoyment of the dwellinghouse. This covers home offices, gyms, art studios, workshops, playrooms, and similar uses.

Key points:

• Working from a garden office for your own employment is generally considered incidental use
• Running a business that involves regular visits from clients, employees, or deliveries may cross the line into a change of use, which requires planning permission
• The building should be subordinate to and associated with the main house, not a self-contained unit

On designated land (conservation areas, AONBs, National Parks, World Heritage Sites), outbuildings must not contain sleeping accommodation.

On non-designated land, there is no explicit ban on sleeping accommodation in the GPDO. However, if the outbuilding is used as a separate dwelling (self-contained living), this would constitute a change of use and require planning permission. An outbuilding used as occasional guest accommodation that remains incidental to the main house is generally acceptable.

Most small outbuildings do not require building regulations approval. However, building regulations do apply if:

• The floor area exceeds 15m² (if it contains sleeping accommodation) or 30m² (general exemption)
• The building is within 1m of a boundary and is not substantially non-combustible
• Electrical work is being carried out (Part P applies to garden offices with fixed wiring)

See our building regulations guide for more on the difference between planning permission and building regs.