Domestic Installer Course: Part P Certification

Domestic electrical work represents the largest segment of the UK electrical installation market. From consumer unit replacements and kitchen rewires to bathroom installations and EV charger circuits, the demand for qualified domestic installers is consistent and growing.

Understanding Part P of the Building Regulations is essential for any electrician working in dwellings. Part P governs which work must be notified to building control, what competence is required, and what documentation must be provided. Getting it wrong can result in enforcement action, invalidated home insurance, and serious problems for homeowners trying to sell their property.

This comprehensive Elec-Mate course covers everything from Part P basics through to advanced domestic wiring scenarios. Whether you are an apprentice studying for your qualifications, a newly qualified electrician preparing to join a competent person scheme, or an experienced electrician refreshing your knowledge of the latest regulations, this course provides the detailed, practical knowledge you need.

Part P (Electrical Safety — Dwellings) was introduced in 2005 to address the high number of domestic electrical fires and accidents caused by poor-quality electrical work. It forms part of the Building Regulations 2010 (as amended) for England and Wales and places a legal requirement on anyone carrying out electrical installation work in dwellings.

The core requirement of Part P is that electrical installation work must be designed, installed, inspected, and tested in accordance with BS 7671 (the IET Wiring Regulations). This means the work must provide reasonable protection against fire caused by the electrical installation and against electric shock to persons and livestock.

Part P applies to all types of dwelling: houses, flats, maisonettes, bedsits, and the common parts of blocks of flats and sheltered housing. It also applies to electrical work in garden buildings (sheds, outbuildings) and conservatories if they are associated with a dwelling. It does not apply to commercial premises, industrial buildings, or common areas of commercial developments.

Scotland does not use Part P — instead, electrical work in Scottish dwellings is governed by the Building (Scotland) Regulations 2004 and the associated Technical Handbooks. Northern Ireland has its own building regulations. The Elec-Mate course focuses primarily on England and Wales but highlights key differences for other regions.

The concept of notifiable work is central to Part P. Certain types of electrical work in dwellings must be notified to the local authority building control body before or after the work is carried out. This can be done either by applying directly to building control (which involves an inspection fee and a visit by a building control officer) or by self-certifying through a Competent Person Scheme.

Notifiable work includes: installing a new circuit (including full or partial rewires), replacing a consumer unit or distribution board, any electrical work in a special location defined in BS 7671 Section 701 (bathrooms), Section 702 (swimming pools), or Section 703 (saunas), any addition or alteration to an existing circuit in a special location, and installing outdoor wiring that is not supplied from an existing circuit via a fused connection unit.

Non-notifiable work includes: replacing existing accessories (socket outlets, light switches, ceiling roses, light fittings) on a like-for-like basis, replacing damaged cable sections, adding a fused spur from a ring circuit or radial circuit (outside special locations), adding a lighting point to an existing circuit (outside special locations), and installing equipment with a rating up to 50V AC or 120V DC.

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Competent Person Schemes are the standard route for electricians to self-certify their domestic electrical work without needing to involve the local authority building control body. Registration with a scheme saves time, reduces costs for homeowners, and demonstrates professional competence.

The main schemes for domestic electrical work are: NICEIC (National Inspection Council for Electrical Installation Contracting) — the largest and most established scheme, NAPIT (National Association of Professional Inspectors and Testers), ELECSA (Electrical Self-Assessment), STROMA, and BRE (Building Research Establishment). All operate under government authorisation and are listed in Schedule 3 of the Building Regulations.

When registered with a scheme, you can self-certify notifiable work by completing the appropriate certificate (EIC, Minor Works, or EICR), submitting the notification through the scheme's portal, and providing the certificate to the homeowner. The scheme body issues a Building Regulations compliance certificate on your behalf, which is registered with the local authority.

Membership requirements typically include: Level 3 electrical qualification, current BS 7671 (18th Edition) certificate, inspection and testing qualification (City & Guilds 2391 or equivalent), public liability insurance, calibrated test equipment, and evidence of CPD.

Domestic electrical installations must comply with BS 7671:2018+A2:2022 (the 18th Edition of the IET Wiring Regulations). While the fundamental principles are the same as any electrical installation, domestic properties have specific design considerations and regulatory requirements.

A modern domestic installation typically includes: lighting circuits (one per floor, 6A MCB or RCBO), ring circuits for socket outlets (32A), dedicated radial circuits for high-power appliances (cooker, electric shower, immersion heater), a dedicated circuit for electric vehicle charging, and potentially circuits for fire alarm systems and solar PV or battery storage.

Circuit design must account for maximum demand using appropriate diversity factors from BS 7671 Table 1C or the On-Site Guide. This determines the total expected load and helps select the correct incoming supply rating. For most domestic properties, a 60A or 80A single-phase supply is standard, though larger properties or those with high-power appliances may require a 100A supply.

Cable sizing must account for the installation method (clipped direct, in conduit, within thermal insulation), ambient temperature, grouping with other cables, and voltage drop. The correction factors can significantly affect the required cable size, particularly for cables run within thermal insulation in loft spaces — a very common scenario in domestic work.

Consumer unit replacement is one of the most common domestic electrical jobs, and it became notifiable work in 2016. Understanding the current consumer unit regulations is essential for every domestic installer.

Non-combustible enclosure: Amendment 4 to Approved Document B (Fire Safety) introduced a requirement for consumer units in domestic premises to be enclosed in a non-combustible enclosure. In practice, this means using a metal consumer unit, which is now the industry standard for new installations and replacements.

RCD protection: BS 7671 requires that all circuits in a domestic property have RCD protection with a rated residual operating current not exceeding 30 mA. The most common arrangement is to use RCBOs (combined MCB and RCD) for each circuit, providing individual circuit protection without the risk of a single RCD trip disconnecting multiple circuits.

AFDD (Arc Fault Detection Devices): BS 7671 Section 421 recommends the use of AFDDs for final circuits in certain domestic premises, including HMOs, care homes, student accommodation, and properties with thatched roofs. While currently a recommendation rather than a requirement, AFDDs are expected to become mandatory in future amendments.

Surge protection: Regulation 443.4.1 requires protection against transient overvoltages to be provided where the consequence caused by the overvoltage could result in (a) serious injury to, or loss of, human life, or (c) significant financial or data loss — note that limb (b) was deleted by the BS 7671:2018+A2:2022 Corrigendum (May 2023). For all other cases, protection must be provided unless the owner of the installation declares it is not required because any loss or damage is tolerable and they accept the risk of damage to equipment and any consequential loss. In practice, SPDs (Surge Protection Devices) are increasingly fitted as standard in new domestic consumer units.

BS 7671 defines several special locations that have additional requirements beyond the general rules. For domestic installers, bathrooms (Section 701) are by far the most commonly encountered special location.

Bathrooms (Section 701) are divided into zones based on proximity to the bath or shower. Zone 0 is inside the bath or shower tray itself — only SELV (Separated Extra-Low Voltage) at 12V maximum is permitted, with equipment rated at least IPX7 (water immersion). Zone 1 extends above the bath or shower to a height of 2.25 metres from the floor — equipment must be rated at least IPX4 (splash-proof) and only SELV or equipment specifically designed for the zone is permitted. Zone 2 extends 0.6 metres horizontally from the outer edge of Zone 1 — equipment must be rated at least IPX4.

Outside the zones (the remainder of the bathroom), standard equipment may be used but socket outlets are not permitted unless they are SELV or shaver sockets complying with BS EN 61558-2-5. Supplementary equipotential bonding of all extraneous-conductive-parts (metal pipes, metal baths) and exposed-conductive-parts is required unless the entire installation is protected by 30 mA RCDs and all circuits meet the requirements of Regulation 701.415.2.

All electrical work in a bathroom is notifiable under Part P, regardless of whether it is a new circuit or an alteration to an existing circuit. Even fitting a new light fitting in a bathroom is notifiable work.

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