Do I Need Planning Permission for an Outbuilding?

Class E covers a wide range of structures, provided they are within the curtilage (garden and grounds) of the dwellinghouse and are for purposes incidental to the enjoyment of the house. This includes:

• Sheds and storage buildings
• Garages and car ports
• Garden offices and studios
• Home gyms and games rooms
• Workshops and hobby rooms
• Summer houses and garden rooms
• Swimming pools and sauna buildings
• Greenhouses

The key test is that the outbuilding serves the main house. It must not function as a self-contained dwelling in its own right.

The height limits for outbuildings depend on the roof type and the proximity to boundaries:

• Dual pitched (apex/gable) roof — maximum overall height of 4 metres.
• Any other roof type (flat, mono-pitch, hip) — maximum overall height of 3 metres.
• Eaves height — maximum 2.5 metres in all cases.

However, there is a critical additional rule:

• If the outbuilding is within 2 metres of any boundary, the maximum overall height is restricted to 2.5 metres, regardless of roof type.

This 2-metre boundary rule is one of the most commonly overlooked restrictions. It effectively means that any outbuilding close to a garden fence must have a maximum height of 2.5 metres — typically ruling out a dual pitched roof at that height and resulting in a flat or very shallow mono-pitch design.

Outbuildings must not be placed forward of the principal elevation of the house. In most cases, this means no outbuildings in the front garden. They are only permitted in the rear and side garden.

The "principal elevation" is normally the front of the house — the elevation that faces the road and contains the main entrance. On corner plots or houses with unusual layouts, the principal elevation is whichever face of the building is most prominent from public view. If you are unsure, your council’s planning department can advise.

The total area of ground covered by outbuildings and other buildings or structures (excluding the original house) must not exceed 50% of the total curtilage area. This is a cumulative limit that includes:

• All outbuildings (existing and proposed)
• All extensions to the house
• Any other structures such as raised platforms, swimming pools, and garden walls over a certain height

The calculation uses the curtilage of the original house, excluding the footprint of the original house itself. If you have a small garden, this limit can be reached surprisingly quickly, especially if there are already sheds, a garage, or extensions on site.

The outbuilding must be used for a purpose incidental to the enjoyment of the dwellinghouse. This is a broad category and includes most reasonable domestic uses:

• A home office where you work from home
• A gym or yoga studio for personal use
• A workshop or craft room
• A games room, music room, or hobby space
• Storage for garden equipment, bikes, or tools
• A summer house or covered seating area

The government has confirmed that working from home in a garden office is an incidental use, provided the building primarily serves the household and is not a separate commercial premises.

An outbuilding that contains sleeping accommodation is explicitly excluded from permitted development. This means you cannot build a self-contained granny annexe, guest bedroom, rental unit, or any structure used as a separate dwelling under Class E.

The test is about the use, not just the physical features. A garden room with a sofa bed that is occasionally used by overnight guests is a grey area — but a purpose-built studio with a bed, kitchen, and bathroom that functions as an independent living space would not qualify as incidental. If challenged, the council would look at the overall character and use of the building.

If you want to build a self-contained annexe, you will need full planning permission. Some councils are supportive of annexe applications, particularly for family members, but the rules and policies vary by area.

Swimming pools, hot tubs, and tennis courts fall within Class E, provided they are incidental to the house and meet the coverage and location rules. A swimming pool counts towards the 50% coverage limit.

Hot tubs are treated as a chattel (moveable item) rather than a structure, so in most cases they do not require planning permission at all. However, if a hot tub is permanently installed with fixed plumbing and a surrounding raised deck, the deck may count as a raised platform and fall outside permitted development if it is more than 300mm above ground level.

If you are building a pool house or sauna building to go alongside a pool, that building must independently meet the Class E height and location rules.

If your property is in a conservation area, national park, Area of Outstanding Natural Beauty (AONB), World Heritage Site, or the Broads:

• Outbuildings with a floor area exceeding 10 square metres are not permitted development if they are more than 20 metres from any wall of the house.
• Outbuildings to the side of the house are not permitted development on designated land.
• Outbuildings that are within 20 metres of the house and in the rear garden still qualify under the normal rules.

Listed buildings do not benefit from Class E rights. Any outbuilding within the curtilage of a listed building requires listed building consent and may also need planning permission.

Many outbuildings are exempt from building regulations if they meet certain criteria:

• The floor area is less than 15 square metres and contains no sleeping accommodation.
• The floor area is between 15 and 30 square metres, contains no sleeping accommodation, and is either at least 1 metre from any boundary or constructed of substantially non-combustible materials.

If the outbuilding exceeds 30 square metres, or contains sleeping accommodation, full building regulations approval is required.

Regardless of floor area, electrical work in an outbuilding must comply with Part P of the building regulations. New circuits must be either installed by a registered electrician (who will self-certify) or inspected by building control. Plumbing for a WC or kitchenette may also trigger building regulations requirements for drainage.

For small sheds and simple storage buildings, most homeowners do not apply for an LDC. However, for larger outbuildings — particularly garden offices, studios, or anything with electrics and plumbing — a Lawful Development Certificate provides formal confirmation that the structure is lawful.

This is increasingly important for garden offices, which have become very common since 2020. If a future buyer or their solicitor questions whether the building needed planning permission, an LDC provides a definitive answer. The fee is £258.