First and Second Fix Electrical Work Explained

When planning a renovation, loft conversion, or new build in the UK, the terms first fix and second fix will come up quickly in conversations with your electrician or main contractor. Understanding what each phase covers — and when it happens in the build sequence — helps you coordinate trades, budget accurately, and avoid costly delays caused by work being done out of order or positions being changed after plastering.

Key points

• First fix covers all electrical work installed before plastering: cables, back boxes, and conduit, typically run while walls are open or studded.
• Second fix covers everything installed after plastering and decoration: sockets, switches, light fittings, the consumer unit, and all final connections and testing.
• Part P of the Building Regulations (England and Wales) requires that most notifiable domestic electrical work is either carried out by a registered competent person under a government-approved scheme (such as NICEIC or NAPIT) or inspected and approved by building control.
• An Electrical Installation Condition Report (EICR) is a separate, periodic inspection of an existing installation — it is not a completion document for new first or second fix work.
• The Part P compliance certificate issued at second fix sign-off is a legal document: keep it with your property deeds, as it will be requested during any future sale or remortgage.

What happens during first fix electrical work

First fix is all the hidden electrical infrastructure installed while walls, ceilings, and floors are open or before plastering begins. During this phase, your electrician will:

• Run cable routes from the proposed consumer unit position to each outlet, light, switch, and socket location throughout the property.
• Install back boxes — the metal or plastic enclosures into which sockets and switches will later clip — set flush into the wall surface.
• Position conduit or cable clips to protect and route cables where required, such as in solid floors or within the defined safe zones in walls set out by BS 7671 (the IET Wiring Regulations, 18th edition).
• Leave cable tails in temporary protective covers, ready for the second fix stage.
• Plan for future circuits: EV charger supply wiring, electric shower, cooker circuit, and outdoor supplies are far more cost-effective to include at first fix than to add retrospectively.

First fix typically takes place after structural work (stud walls, joists) is complete but before the plasterer arrives. Timing is critical — re-opening plastered walls to alter cable routes or move back boxes is expensive and disruptive.

What happens during second fix electrical work

Second fix takes place after plastering is complete and, ideally, after the first coat of decoration. The electrician returns to:

• Fit sockets, switches, and light fittings to the prepared back boxes and cable tails.
• Install and connect the consumer unit (fuse board), including all circuit breakers, RCDs, and RCBOs as required by BS 7671.
• Commission the installation, test each circuit, and produce test certificates.
• Submit a completion notification to the relevant body — either the competent person scheme or building control — satisfying Part P requirements and triggering the issue of a compliance certificate.

Second fix is the point at which the installation becomes functional and legally compliant documentation is generated.

First fix vs second fix: comparison

Homeowner checklist: what to confirm before each stage

Before first fix begins:

• Agree the full circuit schedule with your electrician — number of sockets per room, lighting circuits, dedicated appliance circuits (oven, shower, EV charger).
  
• Finalise positions of all sockets, switches, and light fittings against your room layout before cables are run.
  
• Confirm that chases, voids, or service runs are open and accessible — check with your builder or main contractor.
  
• Establish whether the existing consumer unit will be upgraded or relocated, as this affects cable routing from the outset.
  
• Discuss future-proofing: solar PV readiness, smart home wiring, and EV charging points are all more cost-effective at first fix.
  

Before second fix begins:

• Confirm plastering is complete and sufficiently dry — traditional plasters typically need four to six weeks before decoration.
  
• Agree the specification for socket and switch faceplates and any light fittings the electrician will supply and install.
  
• Ensure any new supply connection or DNO notification is arranged if this is an entirely new installation.
  
• Ask your electrician which Part P route they are using (competent person scheme or building control) and confirm you will receive the compliance certificate on completion.
  

Who can carry out first and second fix electrical work?

In England and Wales, domestic electrical work is governed by Part P of the Building Regulations 2010. Most new circuits, consumer unit replacements, and work in special locations — kitchens, bathrooms, and outdoors — are notifiable, meaning they must either be:

1. Carried out by a registered competent person under a government-approved scheme such as NICEIC, NAPIT, or ELECSA. These electricians self-certify and issue the homeowner with a compliance certificate directly.
2. Carried out by any electrician, but subsequently inspected and approved by a building control officer before the work is signed off.

Option 1 is the most common route for domestic renovation work. Always ask which competent person scheme your electrician is registered with, and request evidence of registration, before work commences.

In Scotland, electrical requirements are governed by the Building (Scotland) Regulations 2004, which differ from Part P.

When to get professional help

Domestic electrical installation — including new circuits, consumer unit work, and work in kitchens, bathrooms, or outdoors — is not suitable for DIY. Always use a qualified, NICEIC- or NAPIT-registered electrician. Consider seeking additional professional input if:

• You are purchasing a property and are unsure whether existing electrical work was properly notified and certificated — an Electrical Installation Condition Report (EICR) can assess the installation's condition and flag uncertified work.
• Your renovation involves both electrical work and wider changes requiring building control sign-off, in which case building regulations drawings may be needed to demonstrate overall compliance.
• You suspect cables were routed outside the required safe zones, or back boxes have become loose or misaligned after plastering.

How Housey can help

Housey connects homeowners with NICEIC- and NAPIT-registered electricians for first and second fix work across the UK. For completed installations — particularly before a sale, remortgage, or tenancy change — an Electrical Installation Condition Report (EICR) confirms whether the installation meets current standards and identifies any work carried out without proper certification.

Frequently asked questions

When should socket and light positions be decided — before or during first fix?

Positions should be finalised before first fix begins. Once cables are run and back boxes are fixed into plaster, relocating them means re-opening walls — adding cost and delay. Your electrician, builder, and any interior designer should agree a full layout, including AV, data, or smart home wiring, before the electrician is on site.

How long after first fix before the electrician can return for second fix?

The main constraint is plastering. Traditional sand and cement plaster typically needs four to six weeks to dry before decoration, and second fix should follow the first coat of paint to protect faceplates from splatter. Dry-lining (plasterboard with skim) dries much faster. Your electrician and plasterer should agree a programme at the start of the project.

What certificate should I receive after second fix electrical work?

If the work is notifiable under Part P, your registered competent person electrician should issue a Building Regulations Compliance Certificate via their scheme (NICEIC, NAPIT, or similar). If building control was used instead, they issue the certificate. Keep this document with your property records — solicitors and mortgage lenders will request it during any future sale or remortgage.

Is an EICR the same as the Part P completion certificate?

No. An Electrical Installation Condition Report (EICR) is a periodic inspection of an existing installation — typically required every ten years for owner-occupied homes or on each tenancy change for rentals. The Part P completion certificate is issued when new notifiable work is certified compliant at the time of installation. Both documents are important but serve entirely different purposes.

Sources and further reading

• Approved Document P: electrical safety — GOV.UK
• IET Wiring Regulations (BS 7671) — IET
• NICEIC competent person scheme — NICEIC
• Electrical safety in the home — Electrical Safety First