Permitted Development for Outbuildings and Garden Rooms

The height limits that decide most cases

• The height limit is 4 metres for a building with a dual-pitched roof, 3 metres in any other case, and 2.5 metres if any part of the building is within 2 metres of the boundary of the curtilage. (MHCLG, September 2019)

• The 4 metre dual-pitched allowance also applies to hipped roofs with slopes on all four sides. (MHCLG, September 2019)

• Eaves must not exceed 2.5 metres, and height is measured from the highest ground level immediately next to the building to its highest point. (MHCLG, September 2019)

• The building must have a single storey. Anything with more than one storey needs planning permission. (MHCLG, September 2019)

Position and the 50% rule

• Nothing may be placed forward of a wall forming the principal elevation of the original house, including anywhere in front of a hypothetical line drawn through that elevation to the side boundary. (MHCLG, September 2019)

• Total ground covered by buildings, enclosures and containers other than the original house must not exceed 50% of the curtilage. Extensions, existing sheds and detached garages all count, including ones built before 1948. (MHCLG, September 2019)

The use test that catches garden offices

• Class E only covers buildings required for a purpose incidental to the enjoyment of the house. MHCLG guidance gives sheds, storage buildings, garages and garden decking as examples. (MHCLG, September 2019)

• It expressly does not cover normal residential uses: separate self-contained accommodation, or the use of an outbuilding for primary living accommodation such as a bedroom, bathroom or kitchen. (MHCLG, September 2019)

• A home office, gym or studio is generally incidental and fine. Put a bed, a shower and a kitchenette in the same building and it stops being incidental, which is why so many garden annexes need permission even though the structure itself is within every size limit.

• Outbuildings are not permitted development where the house was created through a permitted development change of use under Classes M, N, P, PA or Q. (MHCLG, September 2019)

Building regulations and the 1 metre rule

• The often-quoted 1 metre rule is a building regulations fire-safety point, not a planning rule, and the two get confused constantly. Planning uses the 2 metre boundary distance to set the 2.5 metre height limit; building control uses 1 metre to decide what the walls can be made of.

• For certainty that a garden building is lawful, a certificate of lawfulness for proposed development gives a formal council decision, and its lawfulness is then conclusively presumed unless there is a material change before work begins. (legislation.gov.uk, September 2026)

Common questions

How tall can a garden room be without planning permission?

2.5 metres if any part sits within 2 metres of a boundary. Otherwise 3 metres, or 4 metres with a dual-pitched roof. Eaves must stay under 2.5 metres in every case.

Do I need planning permission for a garden office?

Usually not. A home office is incidental to the enjoyment of the house, so it falls within Class E provided the size, position and height limits are met. It changes if the building gains a bedroom, bathroom or kitchen and becomes living accommodation.

Can I put a garden room in my front garden?

Not under permitted development. Nothing may sit forward of the principal elevation of the original house, so a front garden building needs planning permission.

Sources