Installation Checklists
Step-by-step checklists for first fix, second fix, new builds, domestic rewires, and CU upgrades
First fixSecond fixRewireCU upgrade
First Fix Checklist
First fix covers all concealed wiring and infrastructure before plastering. Methodical first fix prevents costly rework.
First fix tasks
BS 7671:2018+A2:2022, IET On-Site Guide| Task | Detail | Standard/Reference |
|---|---|---|
| Cable route planning | Determine routes following safe zones (BS 7671 Reg 522.6.06). Mark horizontal and vertical runs from accessories. | BS 7671 Reg 522.6 |
| Back box installation | Cut out and fit metal or dry-lining boxes at correct heights. Standard: sockets 300mm, switches 1200-1350mm from FFL. | Building Regs Part M |
| Containment installation | Fit conduit, trunking, or cable tray as required. Ensure capacity for cable fill (45% for trunking). | BS 7671 Appendix 12 |
| Cable pulling and clipping | Run cables through routes, clip at correct intervals (Table 4A of On-Site Guide). Leave tails at back boxes. | IET On-Site Guide |
| Fire stopping | Seal all penetrations through fire-rated walls, floors, and ceilings with approved fire-stop products. | Building Regs Part B |
| Consumer unit carcass | Mount CU enclosure in agreed position. Ensure metal CU is earthed and accessible. | BS 7671 Reg 421.1.201 |
| Carcass wiring | Terminate all circuit cables at the CU. Label each cable with circuit reference. Do not energise. | BS 7671 Chapter 51 |
Photograph cable routes before plastering — this creates a permanent record of concealed wiring locations.
Safe Zones
Cables installed in walls must be within prescribed safe zones: 150mm from the top of the wall, within 150mm horizontally from a corner, or within 150mm of either side of an accessory running vertically or horizontally to the accessory. Cables outside safe zones must be protected by 30 mA RCD or mechanical protection.
Second Fix Checklist
Second fix is the visible stage after plastering. Attention to detail here directly affects the finished quality.
Second fix tasks
BS 7671:2018+A2:2022| Task | Detail | Standard/Reference |
|---|---|---|
| Terminations | Strip cables, terminate at accessories. Ensure correct polarity and tight connections. Fold conductors neatly into back boxes. | BS 7671 Section 526 |
| Faceplate fitting | Fit switches, sockets, and data plates. Check level and alignment. Use brass screws in metal plates. | Manufacturer instructions |
| Luminaire installation | Mount ceiling roses, battens, and downlights. Verify fire rating of downlight covers in fire-rated ceilings. | BS 5266, BS 7671 |
| Fixed appliance connections | Connect cooker points, fused spurs, fan isolators, immersion heaters, towel rails. | BS 7671 Section 559 |
| Consumer unit final wiring | Terminate all circuits onto MCBs/RCBOs. Install circuit identification chart. Tighten all terminations to torque. | BS 7671 Reg 514.8 |
| Labelling | Label all circuits at the CU. Label isolators, switches, and distribution boards. Mark RCD test frequency. | BS 7671 Reg 514.9 |
| Testing | Complete full schedule of tests: continuity, insulation resistance, polarity, Zs, Ze, PFC, RCD operation. | BS 7671 Chapter 64 |
New Build Checklist
New-build installations follow the construction programme. Close coordination with other trades is essential.
New-build installation stages
BS 7671, Building Regs Part P, NHBC Standards| Stage | Tasks | Key Considerations |
|---|---|---|
| Site assessment | Review architect drawings, determine CU position, identify special locations, plan cable routes. | Confirm DNO supply position and earthing arrangement (TN-C-S or TT) |
| Infrastructure pre-wiring | Install floor ducts, conduit in slab, underground services (SWA for external lighting, EV charger). | Coordinate with groundworks contractor. Ensure correct depth and sand surround for SWA. |
| Shell first fix | Run all cables in walls and ceilings before insulation and plasterboard. Install back boxes. | Work with plumber and HVAC. Avoid cable crossings where possible. |
| Board first fix | Install CU carcass, meter tails, main earthing terminal, bonding conductors. | Coordinate with DNO for meter position. Install temporary supply board if needed. |
| Second fix | Fit all accessories, luminaires, fixed appliances after plastering and decoration. | Protect finishes. Use dust sheets and clean boots on finished floors. |
| Commissioning | Full test and inspection. EIC with schedules. Part P notification. Builder handover pack. | Test before final decoration to allow for any rework without damage. |
Domestic Rewire Checklist
A full rewire is the most invasive domestic electrical project. A structured approach minimises disruption.
Rewire stages
BS 7671, IET Guidance Note 3| Stage | Tasks | Notes |
|---|---|---|
| Survey existing circuits | EICR of existing installation. Record supply type, earthing, existing circuit layout. Note asbestos risk. | Pre-work EICR establishes baseline and identifies hazards |
| Customer preparation | Agree scope, CU position, accessory positions, lighting plan. Discuss temporary supply arrangements. | Provide written quotation covering all agreed works |
| Invasive first fix | Lift floorboards, chase walls, drill joists (within notching limits). Run new cables in safe zones. | Joist notching: max depth 1/8 span in central 1/4. Holes: max 1/4 depth in central 1/2. |
| Installation | Install new CU, run all new circuits, fit back boxes, containment, and fire stopping. | Work room-by-room to minimise disruption. Maintain temporary power to essential areas. |
| Termination and test | Second fix all accessories. Complete full test schedule. Rectify any defects found during testing. | Insulation resistance test before any circuit is energised |
| Handover | Issue EIC with schedules of inspection and test results. Part P notification. Customer walkthrough. | Explain RCD test button, circuit chart, and next inspection date |
Allow 5-8 days for a typical 3-bed semi rewire depending on property age and accessibility.
Asbestos Awareness
Properties built before 2000 may contain asbestos in textured coatings (Artex), floor tiles, fuse boards, and cable insulation. If suspected, stop work and arrange testing before proceeding. Disturbing asbestos without proper precautions is a criminal offence under the Control of Asbestos Regulations 2012.
Consumer Unit Upgrade Checklist
A consumer unit upgrade is one of the most common notifiable jobs. A methodical approach ensures safety and compliance.
CU upgrade stages
BS 7671, Building Regs Part P, HSE GS38| Stage | Tasks | Notes |
|---|---|---|
| Pre-work EICR | Test existing installation. Record Ze, PFC, Zs for all circuits. Identify any defects to be rectified. | Essential for specifying correct MCB/RCBO ratings and confirming supply adequacy |
| Safe isolation | Isolate at main switch. Lock off. Prove dead with GS38-compliant voltage indicator. Prove the proving unit. | Follow HSE GS38 and IET safe isolation procedure exactly |
| Disconnection | Label every circuit cable before disconnection. Photograph existing wiring. Disconnect load side first, then supply. | Never trust existing labels — verify each circuit by testing |
| New board installation | Mount new metal CU. Install main switch, RCBOs/MCBs. Terminate meter tails, earthing, and bonding. | Metal consumer unit enclosure is mandatory (Reg 421.1.201) |
| Circuit termination | Terminate all circuits onto appropriate RCBOs/MCBs. Tighten all connections to manufacturer torque settings. | Split load or full RCBO board — both acceptable |
| Testing and labelling | Full test schedule. Install circuit identification chart. Label RCD test reminder. Affix warning labels. | Test all circuits, not just modified ones — the CU change affects the entire installation |
| Part P notification | Notify via competent person scheme or building control within 30 days. | CU replacement is notifiable work under Part P of the Building Regulations |
GS38 Compliance
Your voltage indicator and test leads must comply with HSE Guidance Note GS38. This means: fused test leads with a maximum 20mm exposed probe tip, finger guards, insulated to prevent accidental contact, and in good condition with no damaged insulation. Prove your voltage indicator works on a known live source before and after testing.