Building Regulations for garden rooms and garden homes

Planning and building rules are separate

Planning rules decide whether you can build something, and where. The Building Regulations decide how it must be built: structure, fire safety, insulation, ventilation, drainage and so on. Being exempt from planning doesn't automatically make a building exempt from the Building Regulations.

Garden rooms

• Small detached buildings for recreation or storage, up to 25 m², are generally exempt from the Building Regulations.
• Home offices are less clear-cut. Some commentators argue an office isn't "recreation or storage", so the exemption may not cover it. Build to a sound standard anyway.
• The planning limit rose to 30 m² in July 2026, but that doesn't change Building Regulations thresholds. A room between 25 and 30 m² may need to comply.
• No commencement notice is needed for a garden room that's exempt from planning and doesn't need a fire safety certificate.

Class 3A garden homes

A garden home is a home, so the Building Regulations apply in full: structure, fire safety, ventilation, insulation, drainage and access. The Department of Housing has published an information note on how the Building Regulations and Building Control Regulations apply to these auxiliary dwellings. Talk to your council's building control section before you start to confirm which notices and documents you need.

What always applies

• Electrics: by law, electrical work in your home, including the supply to a garden room, must be done by a registered electrical contractor, who gives you a completion certificate.
• Drainage: new connections to your drains should be done properly by a qualified plumber. See garden rooms with a toilet.
• Planning: the exemption rules on size, position, height and use. See the planning guide.