New build electrical installations must comply with BS 7671, Building Regulations Parts P, L, B, M, and S, EV charging regulations, smoke detector requirements, and SAP calculations. This guide covers every requirement in one place.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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A new build electrical installation is one of the most technically demanding projects an electrician can take on. It requires the design, installation, testing, and certification of a complete electrical system from scratch — from the DNO supply point to every switch, socket, light, and fixed appliance in the property.
Unlike an alteration or addition to an existing installation, a new build has no existing infrastructure. Every aspect must be designed, specified, and installed: the consumer unit (or distribution boards for larger properties), all circuits, cable routes, first fix containment, accessories, smoke and heat detection, EV charging infrastructure, lighting controls, and any specialist systems required by the building specification.
The electrical design for a new build must satisfy multiple regulatory requirements simultaneously — BS 7671, Building Regulations Parts P, L, B, M, and S, the DNO connection requirements, and the building specification agreed with the client or developer. Getting the design right before starting saves time, reduces rework, and ensures the installation passes inspection first time.
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Several parts of the Building Regulations directly affect the electrical design and installation in a new build:
The electrician must coordinate with the developer, architect, and Building Control officer to ensure all requirements are met. Missing a regulatory requirement is discovered at completion inspection and means rework before the completion certificate can be issued.
A new build electrical installation is fully notifiable under Part P of the Building Regulations. This means the work must either be carried out and self-certified by a registered competent person, or notified to Building Control before work starts.
For electricians registered with NICEIC, NAPIT, ELECSA, or another competent person scheme, the process is straightforward: complete the installation, carry out initial verification testing, issue the EIC, and notify Building Control through your scheme. The scheme provider issues a Building Regulations Compliance Certificate to the developer.
For unregistered electricians, Building Control must be notified before work starts. They will inspect at key stages — typically first fix (before plastering) and completion. Building Control charges a fee for each inspection. In practice, most developers require their electrical contractors to be registered with a competent person scheme to avoid the delays and costs of Building Control inspections.
SAP (Standard Assessment Procedure) is the UK Government methodology for assessing the energy performance of new dwellings. Every new build must achieve a minimum SAP rating to comply with Building Regulations Part L. The electrical installation directly contributes to the SAP score through the lighting specification.
The SAP assessor produces a report that the developer submits to Building Control. The electrician's contribution is to confirm the lighting specification — total number of fixed lighting outlets, how many are fitted with efficacious lamps, and the wattage of each fitting. This information should be recorded and provided to the SAP assessor.
The Infrastructure for Electric Vehicles (Charge Points) Regulations 2022 came into force on 15 June 2022. They require every new residential building with associated parking to have at least one EV charge point installed and operational before the building is occupied.
For new build developments with multiple dwellings, every dwelling with a parking space must have a charge point. Dwellings without associated parking are exempt. The developer is responsible for ensuring compliance, and the electrician must issue an EV charger installation certificate for each charge point installed.
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Start free trialBuilding Regulations Approved Document B (Fire Safety) specifies the fire detection requirements for new dwellings. The minimum requirement has been significantly enhanced in recent years — new builds now require more comprehensive detector coverage than existing properties.
At first fix, the interconnect cable must be run between all detector positions. If hardwired interconnection is used, a 3-core and earth cable is typically required (the third core carries the interconnect signal). The cable route must follow BS 7671 safe zones and be accessible at each detector position.
Two protective devices that are increasingly specified in new build installations are AFDDs (Arc Fault Detection Devices) and SPDs (Surge Protection Devices).
BS 7671 Regulation 421.1 recommends AFDDs for circuits in locations with sleeping accommodation, locations with risks due to stored materials, and locations with combustible constructional materials (timber frame). While the regulation uses "recommended" rather than "required", the direction of travel is clear — AFDDs are expected to become mandatory in future editions. Fitting them in new builds now is best practice, particularly in timber-framed properties where an arc fault in concealed wiring could ignite the structural timber.
BS 7671 Regulation 443.4.1 requires protection against transient overvoltages where the consequence of an overvoltage event could result in (a) serious injury to, or loss of, human life, or (c) significant financial or data loss — limb (b) was deleted by the 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. In a modern new build with smart home systems, network equipment, EV chargers, heat pumps, and expensive electronics, the financial or data loss threshold is easily met, so SPDs are expected in virtually every new build installation. A Type 2 SPD fitted at the consumer unit is the standard minimum provision.
Both AFDDs and SPDs add cost to the consumer unit — budget an additional £30-£50 per circuit for AFDDs and £50-£100 for an SPD module. Include these in the initial quote to avoid surprises. Use Elec-Mate's quoting app to price the full new build installation including all protective devices.
Designing the electrical installation for a new build requires consideration of the current and future needs of the property. Good design at this stage prevents expensive alterations later and ensures the installation is fit for purpose for its full lifespan.
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