What is involved in electrical first fix and second fix?

On a new build, a rewire or a major renovation, the electrical installation is done in two main stages: first fix, before walls and ceilings are finished, and second fix, once they are.

First fix

First fix is everything that will end up hidden.

• Cable runs from the consumer unit position to every socket, switch, light and piece of fixed equipment
• Back boxes fixed at the agreed positions and heights
• Containment and ducts: conduit, trunking and ducts for routes that need to be accessible or replaceable, including outdoor ducts
• Provision for other systems: cables or draw wires for data, heating controls, security, AV and lighting control
• Supplies to equipment positions: hob, oven, extractor, shower, heat pump, EV charger, garden

At the end of first fix, the routes are recorded (photographs are the simplest way), and the electrician confirms the work is ready for plasterboard, plaster or screed.

Decide before first fix

This is the stage where changes are cheap. Afterwards they mean cutting into finished walls. Before first fix, settle:

• the kitchen layout, including appliance positions and island sockets
• bathroom layout, including the bath or shower position (it determines the zones)
• furniture and television positions in each room
• lighting positions and how each light will be switched
• where you want outdoor power and lighting
• whether you want lighting control, data points or speakers

Between the fixes

Other trades close the walls and ceilings: plastering, screeding, joinery, decorating. The electrician may return for a temporary connection or to deal with changes, but there is usually a gap.

Second fix

Second fix is everything visible.

• Consumer unit fitted and circuits connected
• Accessories: sockets, switches, fused spurs, data outlets
• Light fittings, downlights, LED tape and drivers
• Connections to cookers, hobs, showers, extractors and other fixed equipment

Second fix usually follows decoration, or at least the first coat, so faceplates are not painted around.

Testing and certification

The completed installation is inspected and tested: continuity, insulation resistance, polarity, earth fault loop impedance and RCD operation. You receive an Electrical Installation Certificate and, because new circuits are notifiable, Building Regulations notification. See electrical work and Building Regulations.

For new-build and renovation installations in Yorkshire, see new builds and renovations.