A Guide to Rewiring a House or Extension (UK)

When Does a House Need Rewiring?

You’ll typically need to rewire a house if the electrical installation is more than 25–30 years old. However, age isn’t the only reason. Several warning signs could indicate your home’s wiring is outdated or potentially hazardous. These include:

• Frequent tripping of the consumer unit or RCD

• Fuses that blow regularly

• Buzzing, crackling, or heat from sockets

• Presence of rubber, lead-sheathed, or fabric-insulated wiring

• Black burn marks or signs of melting around outlets

• Cast iron or Bakelite switches

• No RCD protection or circuit labelling

• Wooden-backed fuse boards or consumer units

• Fewer than two sockets per room

• Use of two-pin sockets or overheating plugs

• Note: All electrical work must be performed by a Part P registered electrician to comply with UK Building Regulations.

What’s Involved in Rewiring a House?

At its core, rewiring a house involves removing outdated electrical cables and accessories, then replacing them with modern equivalents that meet current safety regulations. The process typically includes:

• Removing and replacing all fixed wiring

• Installing a modern consumer unit with RCD/RCBO protection

• Chasing walls or lifting floorboards to route new cables

• Adding or relocating switches, sockets, and lighting circuits

• Wiring for smart tech, CCTV, alarms, and data points

• Fitting optional extras like EV chargers or extractor fans

A typical rewire is completed in two stages: the first fix and second fix phases.

First Fix: Structural Electrical Work

The first fix phase begins before plastering or decoration and includes all hidden cabling work:

• Chasing into walls and lifting floorboards

• Fitting new back boxes

• Running new power and lighting circuits

• Routing cables for smoke detectors, alarms, doorbells, and data

To ensure compliance with UK safety standards, make sure to follow strict guidelines when chasing walls:

Chasing Rules (from BS 7671 – 18th Edition):

• Vertical chases: Max one-third of wall thickness

• Horizontal chases: Max one-sixth of wall thickness

• Never chase both sides of a wall in the same location

• All chases must be straight — avoid diagonal routes

• Follow safe zones, e.g., 150mm from wall edges or directly above/below switches and sockets

Checkout the BS 7671 – 18th Edition IET Wiring Regulations…. Here

Second Fix: Finishing & Final Connections

Once plastering and structural work are complete, the second fix stage begins. This step focuses on fitting accessories and final connections, including:

• Wiring in faceplates, sockets, and switches

• Installing pendant lights, spotlights, and wall fittings

• Connecting cookers, electric showers, and extractors

• Making final links to the consumer unit

• Performing safety testing and issuing certificates

Every new or altered circuit must be thoroughly tested by the electrician, followed by the provision of a certificate of compliance.

What Is an Electrical Installation Condition Report (EICR)?

An EICR is a vital document provided after a full inspection of your property’s electrical system. Only qualified electricians can issue one. It helps identify:

• Wear, damage, or deterioration in fixed wiring

• Non-compliance with BS 7671 standards

• Potential hazards such as electric shock or fire risks

Types of EICR:

• Visual Condition Report – Limited to visible checks (suitable for newer installations)

• Periodic Inspection Report – Full testing of all circuits, including hidden cabling and fixed wiring

Frequency:

• Every 10 years for homeowners

• Every 5 years for landlords

• Every change of occupancy

Any findings listed as C1 (danger present), C2 (potentially dangerous), or FI (further investigation required) must be resolved before the system can be considered safe.

UK Wiring Regulations (18th Edition – BS 7671)

All rewiring work must comply with:

• BS 7671 – IET Wiring Regulations (18th Edition)

When rewiring a house, compliance with UK wiring standards is not optional — it’s the law. You must meet the following:

Key Regulations:

• Follow BS 7671 – IET Wiring Regulations (18th Edition)

• Comply with Part P of UK Building Regulations

• Provide RCD protection on all new circuits

• Route cables within recognised safe zones

• Ensure exposed metal boxes are properly earthed

• Use mains-powered, interlinked smoke/heat alarms

• Match bathroom fittings to appropriate IP ratings

• Perform final tests and issue Electrical Installation Certificates (EICs)

These standards help safeguard property and life while ensuring energy efficiency and long-term reliability.

Essential Tools to Get The Job Done!

Professionals and DIYers will typically need:

• Electrical Tools
• SDS wall chaser or multi-tool
• Cable reels (Twin & Earth, CPC)
• Consumer units with RCD/RCBOs
• Dry lining boxes and metal back boxes
• Surface and flush sockets/switches
• Voltage Testers and Multimeters
• Accessories: insulation tape, grommets, trunking, etc.

Useful Accessories:

• Insulation tape, grommets, trunking, and clips

• IP-rated fittings for wet areas

• Cable management gear for neat installations

Need supplies? View our full Electrical Tools and Power Tools and Accessories collection for certified gear at trade prices.

Final Thoughts on Rewiring a House

A full or partial rewire is a major job — but when carried out correctly, it drastically improves the safety, usability, and future-proofing of any UK home. By following best practices, complying with BS 7671, and using the right tools, you’ll ensure the work is both legally compliant and built to last.

Whether you’re a homeowner planning a project or a professional preparing for a large rewire, make sure you understand the process from first fix to final testing — and always prioritise safety.