East London — from Canary Wharf and Stratford to Hackney and the Royal Docks — has seen rapid commercial development over the past decade. New offices, retail units, restaurants, cafés, and light industrial units are constantly being fitted out. The electrical installation is one of the most complex and consequential parts of any fit-out, and getting it wrong means delays, cost overruns, and failed inspections. This guide explains what's involved and what to look for when choosing a commercial electrician.
What is a commercial electrical fit-out?
A commercial electrical fit-out is the design and installation of all electrical systems within a commercial premises — from the point where the incoming supply enters the building through to every socket, light fitting, and piece of electrical infrastructure your business needs. Depending on the nature of the premises, this can include:
- Main distribution board (MDB) and sub-distribution boards
- Power circuits for workstations, equipment, and machinery
- Lighting — general, task, display, feature, and emergency
- Emergency lighting and fire alarm systems
- Data and comms containment (cable management for IT cabling)
- Three-phase supplies for heavy equipment, commercial kitchens, or lifts
- CCTV, access control and intruder alarm circuits
- External lighting and signage feeds
- EV charging points for staff or customer parking
Cat A vs Cat B fit-out — what's the difference?
Commercial fit-outs are commonly described in two categories:
- Cat A — the base build. The landlord or developer brings the building to a basic usable standard: power to the floor, lighting to common areas, fire alarm connected to the main system, and services terminated ready for the occupier. When you take on a new commercial lease, this is usually what you receive.
- Cat B — the occupier's fit-out. This is where you configure the space for your specific business: partitioning, feature lighting, power to workstations, kitchen equipment, CCTV, data points, signage feeds — everything that makes the space yours. This is what most businesses mean when they talk about a commercial fit-out.
We work on both — either alongside the main contractor on a Cat A base build, or as the specialist electrical subcontractor for your Cat B occupier fit-out.
Regulations that apply to commercial electrical installations
Commercial electrical installations must comply with several overlapping regulatory frameworks:
- BS 7671 (IET Wiring Regulations, 18th Edition) — the UK standard for all electrical installations, domestic and commercial
- Building Regulations Part B (Fire Safety) and Part M (Access) — govern fire detection, emergency lighting and accessible switch and socket heights in commercial buildings. (Part P applies to dwellings only, so it does not cover commercial premises.)
- Building Regulations Part B (Fire Safety) — sets requirements for fire detection and alarm systems, emergency lighting, and means of escape
- Electricity at Work Regulations 1989 — places duties on employers to maintain electrical systems in a safe condition and to have adequate inspection and testing regimes
- BS 5839 — the standard for fire detection and alarm systems in buildings
- BS 5266 — the standard for emergency lighting
For licensed premises (restaurants, bars, venues), your premises licence conditions may also specify electrical safety requirements such as annual testing of emergency lighting or specific CCTV standards.
What does a commercial electrical fit-out involve, stage by stage?
1. Survey and design
Before any cables are run, we survey the premises and agree on the scope of works with you or your project manager. This involves understanding your power requirements (what equipment will be used and where), lighting preferences, data and comms needs, and any specific regulatory requirements for your industry. We then produce a schedule of works and a fixed price.
2. First fix
First fix is the hidden infrastructure work — running cables through walls, ceilings, and floors before the building fabric is sealed. For commercial premises this typically involves installing containment (cable trunking or conduit), drawing cables through it, and positioning back boxes for sockets, light switches and data points. This stage happens alongside other trades — plastering, dry lining, and carpentry.
3. Distribution board installation
The distribution board (or boards, for larger premises) is the commercial equivalent of a domestic consumer unit. We install and wire the board, connecting all circuits and installing the correct protective devices for each circuit type. For larger premises this may involve three-phase distribution and multiple sub-boards serving different areas or floors.
4. Second fix
Once the building fabric is in place, second fix involves fitting all visible components — socket faceplates, light switches, luminaires, data outlets, and any specialist equipment. This is also when emergency lighting fittings and fire alarm devices are installed.
5. Testing and commissioning
Every circuit is tested with calibrated instruments before the installation is energised. We carry out insulation resistance tests, earth fault loop impedance tests, RCD tests, and continuity tests. For fire alarm and emergency lighting systems, we carry out full commissioning to the relevant British Standard. You receive an Electrical Installation Certificate and, for fire systems, a commissioning certificate — both essential for your building sign-off and insurance.
Emergency lighting in commercial premises
Emergency lighting is not optional in commercial premises — it is a legal requirement under the Building Regulations and BS 5266. Emergency lighting must activate automatically if the mains power fails and must illuminate all escape routes, exits, fire fighting equipment, and first aid points. For most commercial premises, you will need:
- Maintained or non-maintained emergency luminaires on all escape routes and in all rooms that are used by the public or staff
- Illuminated emergency exit signs
- Annual testing and a logbook record — we provide annual test certification
Three-phase supplies — do you need one?
Most standard offices and small retail units can operate on a single-phase 100A supply. However, if you have heavy equipment — commercial catering equipment, large HVAC systems, industrial machinery, multiple EV charge points, or a significant lift installation — you may need a three-phase supply. We can advise on whether your proposed electrical load requires a three-phase connection and, if so, liaise with the Distribution Network Operator (UK Power Networks in East London) on your behalf to arrange the upgraded supply.
Typical timescales and costs
Commercial electrical fit-out costs depend on the size of the premises, the complexity of the installation, and the specification required. As a rough guide, typical London market rates look like this (we quote every commercial job individually):
- Small retail unit or office (up to 100 sq m): electrical fit-out from £3,500–£8,000 depending on specification
- Medium office or restaurant (100–300 sq m): from £8,000–£25,000
- Larger commercial premises: priced on full survey — call for a preliminary discussion
These figures are for guidance only. Every commercial fit-out is different and we always provide a detailed, fixed quote based on your specific drawings and requirements before any work begins.
Timescales vary significantly with project size, but allow at least 2–3 weeks for a small unit and 4–8 weeks for a medium-sized commercial fit-out when working alongside other trades.
Why choose a specialist commercial electrician for your fit-out?
Commercial electrical installations are significantly more complex than domestic work. The regulations are different, the equipment is different, and the consequences of getting it wrong — failed inspections, delays to opening, enforcement action, insurance voidance — are considerably more serious. When choosing your commercial electrician, look for:
- Experience with commercial fit-outs specifically, not just domestic work
- Ability to work alongside other trades to a programme
- Provision of full BS 7671 test certification at completion
- Experience with fire alarm and emergency lighting commissioning
- Public liability insurance appropriate for commercial projects
Royal Docks Electrical has over 28 years of experience in commercial electrical installation across East London. We work with businesses of all sizes — from independent cafés in Hackney to office fit-outs in Canary Wharf and warehouse installations in Barking.