Building Regulations for Garden Rooms and Outbuildings

What This Requirement Covers

Garden rooms, home offices, and outbuildings have become increasingly popular. Whether Building Regulations approval is required depends on the size, construction, and intended use of the structure.

Key Requirements

Exempt Structures

A detached single-storey building within the curtilage of a dwelling is exempt from Building Regulations if

1. The floor area does not exceed 15 m2 and the building contains no sleeping accommodation, OR
2. The floor area is between 15 m2 and 30 m2, the building contains no sleeping accommodation, AND it is either more than 1 metre from any boundary or constructed of substantially non-combustible materials
3. The building is not used for habitable purposes (i.e., not a bedroom, living room, or kitchen)

When Approval IS Required

Building Regulations approval is required if

1. The floor area exceeds 30 m2
2. The building contains sleeping accommodation (e.g., a guest bedroom, home office with a sofa bed)
3. The building includes a WC or shower (drainage requires Building Regulations compliance)
4. The building is connected to the mains gas supply
5. The building is intended as habitable space (a room used for living, sleeping, or cooking)
6. Electrical work is notifiable under Part P

Planning Considerations

Permitted development rights for outbuildings

1. Must be single storey with maximum eaves height of 2.5 metres
2. Maximum overall height: 4 metres (dual pitch) or 3 metres (other roofs) or 2.5 metres if within 2 metres of a boundary
3. Must not cover more than 50% of the garden area
4. Must not be forward of the principal elevation
5. Restrictions apply in conservation areas, listed buildings, and areas with Article 4 directions

Practical Compliance Tips

1. Determine whether the building is exempt before starting design; the exemption criteria are strict
2. If the garden room will be used as a home office with no sleeping, bathroom, or cooking facilities, it may be exempt
3. Be honest about the intended use; a garden room marketed as a bedroom requires Building Regulations approval
4. Even exempt buildings should be constructed safely and to a reasonable standard
5. Consider the impact on neighbours; noise, overlooking, and light may require planning consideration
6. If the building includes electrical installation, check whether Part P notification is required (a competent person scheme electrician can self-certify)
7. Keep records of the building for future property sales; buyers will ask about garden structures