—Wiring and circuits
Wiring for an extension, annex or garden room
A new room needs power, light and protection. Planning the electrics early avoids running cables after walls are finished.
Extensions, annexes and garden rooms often need their own sub-board, fed from the main board. The cable route — through walls, ceilings or underground — must be protected and suited to the distance. The new space may need AC, sockets, lighting and data.
Wiring guides explain how circuits are put together and changed, so a quotation or a recommendation is easier to follow.
Capacity matters. A new room with AC adds significant load, so the main supply and board are checked. Outdoor routes need protection from digging, sun and water. Planning the electrics alongside construction keeps cables hidden and routes sensible.
01In short
The points that matter most
Sub-boards help
They manage circuits in the new space.
Protect cable routes
Especially outdoors.
Check capacity
New AC and appliances add load.
02Detail
Planning elements
Feed cable
Size and route from the main board.
Circuits
Lighting, sockets, AC and outdoor.
Protection
Suitable protective devices.
Lighting and controls
Plan switch positions, outdoor lighting at the new door and any sensor or smart control before walls are closed.
Data and security
Network cable, cameras and intercom points are easier to install with the power cabling.
03Checklist
Before construction
Plan room uses
Office, bedroom, gym or majlis.
List equipment
AC, appliances, lighting.
Coordinate trades
So cables are installed before finishes.
04Questions
Questions people ask
- Does an annex need its own board?
- Often, especially if it has several circuits.
- Can cables run underground?
- Yes, with suitable protection and depth.
- Will the main supply cope?
- Capacity is checked during planning.
- Do approvals affect the electrics?
- The extension’s approval drawings usually include services; the electrical layout should follow the approved plan.
- Can the annex have its own meter?
- That is a supply question decided with the supply authority, not a wiring choice.
05Related
Related guides
- Signs that wiring may need replacingMore on the circuits behind the same problem.
- Rewiring a villaMore on the circuits behind the same problem.
- Surface or concealed wiringA related choice for the same kind of work.
- MCB or RCBOA related choice for the same kind of work.
This guide sits under electrical wiring. All topics are on the guides page.
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