Planning permission asks whether a building is acceptable in that place. Building Regulations ask whether it is built safely. A garden bar can need one, both or neither, and the answer to one does not settle the other.
The size and use starting point
The Planning Portal explains that in England a small detached outbuilding with a floor area under 15 m², and no sleeping accommodation, will not normally need Building Regulations approval. Between 15 m² and 30 m², approval is normally not needed if there is no sleeping accommodation and the building is either at least 1 m from any boundary or built substantially of non-combustible materials.
Bigger buildings, buildings with sleeping accommodation or ones that do not meet those conditions are likely to need approval. A garden bar that becomes a guest room is a different building in regulatory terms.
Electrical work is its own question
Even when the building itself is exempt, electrical installation work has to meet the relevant requirements. Approved Document P covers electrical safety in dwellings, and new circuits to outbuildings are commonly notifiable. In practice, use a registered competent electrician who can self-certify and give you the certificates. See power to a garden bar.
Other areas that can matter
- Fire safety: distance from boundaries and the house, and the materials used, affect fire spread. Approved Document B is the guidance.
- Ventilation: relevant where fuel-burning appliances or habitable rooms are involved; see Approved Document F and our damp and ventilation guide.
- Drainage: a sink connected to drains brings its own requirements; see sink and water.
- Fixed heating appliances: gas and solid-fuel appliances have specific installation rules. See heating.
What to keep
Keep certificates, completion notices and any written advice from building control. They matter when you sell the house, make an insurance claim or change the building's use later.
When to ask
Ask building control before you build if the bar is bigger than 15 m², close to a boundary, attached to the house, includes plumbing or fuel-burning heaters, or might be used for sleeping. A short conversation early is far cheaper than altering a finished building.
Measure the internal floor area and the distance to each boundary, then read the Planning Portal page on outbuildings and Building Regulations. If anything sits near a threshold, ask building control in writing.
Sources
Primary guidance checked 10 November 2026.