Do I Need to Rewire My House When Doing an Extension?

If you’re adding an extension, you might assume you can just extend your existing wiring. In some cases, you can, but if your electrics are old or your new demand is too high, you might need a partial or full rewire.

When Does an Extension Require a Rewire?

1. Your Existing Wiring is Outdated

• If your house was wired before the 1980s, it might still have rubber or fabric-insulated cables, which are a fire risk.

• No earth bonding? You’ll need to upgrade to meet modern safety standards.

2. Your Consumer Unit (Fuse Box) Isn’t Up to Standard

• If your fuse box is old and doesn’t have RCD protection, it won’t comply with modern regulations, and you may need a new one.

• If your extension adds too much demand, your existing board might not have enough capacity.

3. The Extension Requires a Separate Circuit

• Kitchens, bathrooms, and high-power areas (e.g., electric ovens, underfloor heating) often need dedicated circuits.

• If your existing circuits are already near capacity, you’ll need new wiring.

4. You’re Planning Major Alterations

• If you’re knocking through to create open-plan spaces, you might be disturbing existing wiring.

• Moving light switches, sockets, or adding a significant number of new outlets may mean rewiring.

5. Building Regulations Keep Changing

• Even if your property was rewired recently, there’s a high chance it no longer meets the latest regulations.

• Electrical standards are updated regularly, so what was compliant a few years ago may now be outdated.

What If My Wiring Is Fine?

If your existing electrics are modern and up to code, you might just need to extend circuits rather than replace them.

If your wiring isn’t bang up to date but is in good condition, you don’t have to rip it out. Instead, you can:
✅ Leave the existing wiring as it is if it’s safe and functional.
✅ Install all new wiring on a separate consumer unit that meets current standards.
✅ Ensure any new circuits comply fully with the latest regulations.

This approach saves money and avoids unnecessary disruption while keeping your new extension compliant.

How to Avoid Problems

✅ Get an electrical condition report (EICR) before starting work to check if your wiring is safe.
✅ Factor in rewire costs early—if it needs doing, it’s best to do it before walls and ceilings go up.
✅ Use a qualified electrician who understands building regs and Part P compliance.

The Bottom Line

Not every extension needs a full rewire, but if your electrics are outdated, overloaded, or unsafe, you won’t be able to avoid it. Get it checked early so you don’t hit unexpected costs later.

At Bloom Builders, we ensure all electrical work meets current regulations. Need advice? Get in touch.