Do I Need Planning Permission for an Outbuilding?

Most outbuildings in England do not need planning permission. Garden sheds, workshops, home offices, garden rooms and similar structures can usually be built under Class E permitted development rights when they are incidental to the use of the house and stay within specific size and placement limits. However, the 50% curtilage rule and height limits catch many projects, and listed buildings and designated land have much tighter restrictions.

• Not forward of the principal elevation of the house — so usually in the rear or side garden, not the front garden
• Total area covered by all outbuildings and additions does not exceed 50% of the curtilage (the land around the house)
• Single storey only, with maximum eaves height of 2.5 metres
• If within 2 metres of a boundary: maximum overall height of 2.5 metres
• If more than 2 metres from all boundaries: maximum 4 metres for a dual-pitched roof or 3 metres otherwise
• Incidental use only — not sleeping accommodation or a self-contained living space
• No veranda, balcony or raised platform
• On designated land (conservation areas, National Parks, etc.), outbuildings to the side of the house are also not permitted development

This is the key legal test for outbuildings. Permitted development for outbuildings covers structures used for purposes incidental to the enjoyment of the dwelling — such as a hobby workshop, garden office, gym, games room, or storage. It does not cover:

• Sleeping accommodation — a guest bedroom, granny annexe or any room used for sleeping needs planning permission, as the use ceases to be incidental
• Self-contained living space — a structure with kitchen, bathroom and sleeping arrangements is a separate dwelling unit and always requires planning permission
• Commercial use — operating a business from an outbuilding may require planning permission for a change of use

A home office where you work during the day is incidental. An annexe where your elderly relative lives is not. The distinction matters because enforcement action can follow if an outbuilding is used as a separate dwelling without permission.

Height is measured to the highest point of the outbuilding. For a dual-pitched roof, this is the ridge. For a flat or pent roof, it is the top of the highest wall. The 2.5-metre eaves limit applies to the lowest point of the roof slope — this often catches larger buildings with high side walls even if the ridge is within the overall height limit.

The 2-metre boundary rule applies to each boundary independently. If one corner of your outbuilding is within 2 metres of the side fence but all other walls are further away, the 2.5-metre overall height limit still applies because part of the building is within 2 metres of that boundary.

The curtilage is the land that forms part of and is closely associated with the dwelling house. It typically includes the garden, driveway and any land used with the house. It does not usually include paddocks, orchards or land that has been sold off separately.

The 50% curtilage rule applies to all outbuildings and additions combined, not just the one you are building. If previous sheds, greenhouses, or other structures already cover 40% of your curtilage, your new building can only add 10% more.

A garden office, studio or home gym is treated the same as any other outbuilding for planning purposes. As long as it is used for a purpose incidental to the dwelling (not sleeping or living accommodation), it usually qualifies as permitted development within the Class E limits. “Incidental” use can include working from home, creative pursuits, fitness, and hobbies.

• Forward of the principal elevation (for example in the front garden)
• Exceeds height or footprint limits
• Used or intended for sleeping accommodation or as a separate living unit
• Property is a listed building
• On designated land and the outbuilding is to the side of the house
• Total outbuildings exceed 50% of the curtilage
• PD rights removed by Article 4 direction or planning condition

On designated land (conservation areas, National Parks, Areas of Outstanding Natural Beauty, World Heritage Sites), outbuildings to the side of the house are explicitly not permitted development. Rear outbuildings on designated land may still be permitted development if within all other limits. Listed buildings have no Class E permitted development rights at all — any outbuilding, however small, requires planning permission and potentially listed building consent.

Planning permission and building regulations are assessed separately. A small, simple shed may not need building regulations approval, but an outbuilding with electrics, heating, plumbing, or a structural foundation will likely require building regulations sign-off covering electrical safety (Part P), structural design, ventilation, and potentially thermal insulation (Part L). Always check with your local building control body before installing any fixed electrical installation in an outbuilding.

A timber garden shed: £500–£3,000. A prefabricated garden office or studio: £8,000–£30,000. A bespoke brick or timber-frame outbuilding with insulation and electrics: £15,000–£60,000. If planning permission is needed, a householder planning application costs £258. Building regulations fees are additional. No planning application fee is required for permitted development, though you can apply for a Lawful Development Certificate (around £103–£206) to confirm the outbuilding is lawful.

Do I need planning permission for a garden office? Usually not, as long as it is used as a home office (not sleeping accommodation), stays within the Class E height and size limits, and does not exceed 50% of your curtilage.

Can I build an outbuilding right up to my boundary? Yes, but if any part is within 2 metres of a boundary, the maximum overall height is 2.5 metres.

What if I want to rent my garden room out? Renting it as separate accommodation or holiday let changes the use from “incidental” and will require planning permission. Casual occasional use by family members is different from a formal tenancy.