Every house extension involves electrical work. Even a straightforward single-storey rear extension will typically need new lighting, power sockets, and potentially connections to the kitchen or heating system. Part P of the Building Regulations governs electrical safety in dwellings, and it applies to all new electrical installations and significant alterations to existing ones – including those carried out as part of an extension.
For most homeowners, Part P works in the background: a competent electrician handles the work, self-certifies it and notifies the relevant authority on your behalf. But understanding what Part P requires – and what to look out for when appointing your electrician – is still worthwhile.
What Does Part P of the Building Regulations Require?
Building Regulations Part P requires that electrical installations in dwellings are designed and installed to provide protection against:
- Electric shock – through proper earthing, insulation and protective devices
- Electrical fires – through correct cable sizing, appropriate fuses and circuit breakers, and protection against overloading
- Damage to the installation and to other building elements – through correct routing, fixing and protection of cables and equipment
The technical standard that sets out how these outcomes are to be achieved is BS 7671, the IET Wiring Regulations (currently the 18th Edition). All electrical work in dwellings must comply with BS 7671.
Part P also requires that electrical installation work is either carried out by a competent person who can self-certify the work, or is notified to a building control body for inspection and testing.
What Electrical Work is Notifiable Under Part P?
Not all electrical work in a home is notifiable – minor works such as replacing a socket faceplate, changing a light fitting or repairing a fault are generally not notifiable provided the circuit is not in a special location. However, the following types of work are notifiable:
- Installing a new circuit – including any new ring main, radial circuit or lighting circuit
- Replacing a consumer unit (fuse board)
- Adding or altering circuits in ‘special locations’ – kitchens, bathrooms, outdoors, or areas where water is present
For a house extension, a new electrical installation is almost always required, which means new circuits will be added. This is notifiable work. In the context of a kitchen extension – where the special location rules apply throughout – virtually all electrical work is notifiable.
The Self-Certification Route
The most straightforward route to Part P compliance for extension work is to use an electrician who is registered with a government-authorised competent person scheme. The major schemes for domestic electrical work include NICEIC, NAPIT, Elecsa and SELECT. Electricians registered with these schemes can self-certify their work – they test and inspect it themselves, issue a Minor Works Certificate or Electrical Installation Certificate (EIC), and notify the relevant authority on your behalf. You receive a certificate and a copy of the notification, and a record is kept on the database maintained by the scheme.
This route is straightforward for homeowners and does not require any separate engagement with building control for the electrical work. The certificate issued by the registered electrician is the documentation you will need when selling the property.
When appointing an electrician for your extension, it is always worth confirming that they are registered with an approved competent person scheme. A registered electrician will be able to produce their scheme membership card or certificate on request, and you can verify their registration online.
The Building Control Route
If the electrical work in your extension is being carried out by an electrician who is not registered with a competent person scheme, the work must be notified to the local authority building control (or an approved inspector) before it begins. Building control will then arrange for the completed installation to be inspected and tested by a qualified person before issuing approval.
This route is less common for straightforward extension work, but it is a valid option. The practical implication is that it requires coordination between the electrician, the homeowner and building control, and the inspection must be arranged before the installation is covered up (by plastering, boarding or floor coverings). Leaving electrical work uncovered for inspection purposes needs to be factored into the construction programme.
What an Electrical Installation Certificate Covers
Once the electrical installation in your extension is complete, the registered electrician will issue an Electrical Installation Certificate (EIC) for new installations. This document records:
- The details of the installation – circuits, protective devices, cable types and routes
- The results of inspection and testing – earth continuity, insulation resistance, polarity, loop impedance
- The name and qualifications of the designer, installer and inspector
- A declaration of compliance with BS 7671
The EIC is an important document and should be kept with the property’s other building records. It will be required by solicitors when the property is sold, alongside the building regulations Completion Certificate for the extension as a whole. If you cannot produce an EIC for electrical work, you may be asked to commission a periodic inspection report to verify the current condition of the installation.
Special Locations: Kitchens and Bathrooms
Part P identifies certain locations in a home as ‘special locations’ where the risk from electrical installations is higher – primarily because of the presence of water. Kitchens and bathrooms are both special locations, and additional requirements apply to electrical installations in these areas.
In bathrooms, the regulations define ‘zones’ around baths and shower trays within which electrical equipment must not be installed or must meet higher standards of water ingress protection. Only SELV (safety extra-low voltage) equipment is permitted in Zone 1 (directly above the bath or shower tray). In Zone 2 (the area from the rim of the bath or shower tray to a point 600mm horizontally outside it), equipment rated at least IPX4 (splash-proof) is required.
In kitchens, where sockets and outlets are in close proximity to water sources, bonding requirements and the protection of circuits serving appliances are particularly important.
Earthing and Bonding
One aspect of electrical safety that is often overlooked in extensions is the requirement for supplementary bonding. Where a new extension introduces metal pipework for plumbing or heating, or where the extension is a wet room or bathroom, Part P requires that metallic services are bonded to the earth of the electrical installation. This prevents dangerous voltage differences from developing between metallic items in the event of an electrical fault.
Your electrician will be responsible for assessing and carrying out any supplementary bonding required as part of the extension installation. It is worth confirming at the outset that this has been considered, particularly where the extension involves a new kitchen or bathroom.
At Simply Extend
Part P is one of those areas where the right appointment makes everything straightforward. At Simply Extend, we work with qualified, scheme-registered electricians on every project we deliver, ensuring that the electrical installation is designed and built to BS 7671, properly certified and notified without any additional burden on you as the homeowner. The paperwork is handled, the certificates are issued, and the installation is covered as part of our overall building regulations management service.
Planning an extension and want to make sure everything is covered? Get in touch with Simply Extend today for a free site survey and expert advice. Call us on 0800 917 7571 or email info@simplyextend.co.uk and one of our team will be happy to help.
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