From Design to Certificate: How a Commercial Electrical Project Actually Runs

Most commercial electrical projects don’t fail because of bad kit or dodgy wiring. They fail because nobody explained the actual process, so expectations drift, timelines slip, and the certificate arrives three weeks after you needed it.

We’ve run hundreds of commercial electrical jobs across London and Essex, office fit-outs in Canary Wharf, retail units along the A12 corridor, workshops in Romford, restaurants in Shoreditch. The kit changes. The regulations tighten. But the underlying sequence stays the same. Here’s how a proper commercial electrical project actually runs, from the day you call to the day you get your certificate.

Stage One: Initial Enquiry and Site Survey

You call or email. We ask four questions: what’s the building use, what work do you need, when do you need it done, and who’s your landlord or freeholder. That last one matters because it dictates whether we need wayleave agreements, building control involvement, or landlord-approved contractor status.

Within 48 hours, usually sooner, we arrange a site visit. Not a salesman with a clipboard. A qualified electrician or project manager who’s actually going to price and plan the job. We measure up, photograph the existing installation, check the incoming supply, note access constraints (loading bays, working hours, adjacent tenants), and identify any immediate compliance issues that’ll need addressing regardless of your main scope.

If it’s a refurb or fit-out, we’ll want to see existing electrical drawings. Most landlords have them. Most tenants don’t know where they are. We can work either way, but old drawings save time and reduce the risk of expensive surprises when we open things up.

Design and Specification

For anything beyond basic like-for-like replacements, you need a proper design. That means load calculations, circuit schedules, lighting layouts, emergency lighting compliance with BS 5266, and, if you’re adding substantial load, a G99 application to the DNO for grid connection approval.

We produce design drawings in-house. Small jobs might be a marked-up floor plan with a schedule. Larger projects get full CAD schematics, panel schedules, and a written specification. Everything references current BS 7671 (18th Edition, as amended), and we flag anything that needs building control notification under Part P or separate sign-off (fire alarm systems, emergency lighting, EV chargers over 7kW in certain installations).

The design phase is where scope creep lives. A restaurant owner asks for “some extra sockets” and discovers their incoming supply is already at 90% capacity, so now we’re pricing a new substation or three-phase upgrade. A warehouse wants LED replacements and we find the existing distribution board is older than the Spice Girls and needs replacing before we touch anything else. Better to surface this now than halfway through the install.

Typical design turnaround: three to seven working days for straightforward jobs, up to three weeks for complex fit-outs involving multiple services coordination.

Quotation, Approval, and Programme

We send a written quotation breaking down labour, materials, testing, certification, and any third-party costs (building control fees, DNO charges, crane hire, traffic management). We itemise variations separately so you can see what’s essential and what’s optional.

Once you accept, we agree a programme. Commercial work almost always has constraints: you can’t shut the tills during trading hours, you can’t isolate the server room without IT sign-off, you can’t drill through a suspended ceiling until the asbestos survey comes back. We build the programme around your constraints, not ours.

Lead time from order to start varies. If it’s a board swap or lighting upgrade using stock kit, we can often start within a week. If it’s a full fit-out needing custom panels, long-lead switchgear, or specialist luminaires, allow four to eight weeks. Right now, EV chargers and certain smart panels are running eight to twelve weeks from European suppliers.

We also arrange statutory notifications at this stage. Building control gets notified before we start (not after, despite what some cowboys do). If it’s a new supply or significant alteration, the DNO application goes in. If it’s a licensed premises or care home, we coordinate with the local authority. Paperwork’s boring. It’s also non-negotiable.

Installation and Testing

The actual installation is the bit most people think is the whole job. It isn’t. It’s typically 40, 60% of the timeline.

We start with isolation and prove-dead testing on anything we’re working on. Then first fix: cable runs, back boxes, conduit, trunking. If it’s new-build or a shell, this happens before the ceiling and walls go up. If it’s a refurb, we’re often chasing into plaster or threading through voids, which is slower and messier.

Second fix follows: terminations, accessories, luminaires, panel wiring. Everything gets labelled as we go, circuits, breakers, isolators. You’d be amazed how many sparks skip this. Then when something trips in two years’ time, nobody knows which breaker feeds which socket.

Once installation’s complete, we test. Every circuit. Dead tests (continuity, insulation resistance, polarity). Live tests (earth fault loop impedance, RCD trip times, voltage drop under load). Emergency lighting gets a full duration test, usually three hours. Fire alarms get a zone-by-zone functional test. We record everything in the test sheets that’ll form part of your electrical installation certificate.

If something fails, we fix it and retest. No shortcuts. No “it’ll probably be fine.” You’re paying for a compliant installation, and that’s what you get.

Certification and Handover

This is where a lot of contractors fall down. They finish the install, pack up, send an invoice, and never mention certification. Then six months later you need to show an electrical certificate for insurance or a lease renewal, and it doesn’t exist.

We issue an Electrical Installation Certificate (EIC) for new installations or alterations, or a Minor Electrical Installation Works Certificate (MEIWC) for small additions to an existing installation. Both are signed by the designer, installer, and inspector, sometimes the same person, sometimes not. Both include full test results and a schedule of items inspected.

You also get a schedule of circuit details for your distribution board, emergency lighting certificates (if applicable), and any manufacturer warranties or commissioning sheets for specialist kit. If building control was involved, we liaise with them for final sign-off. If the DNO needed to witness anything (new supply, generator connection), we arrange that too.

Everything goes in a labelled folder or digital pack. Keep it. You’ll need it for your next EICR (periodic inspection), which is due every five years for commercial premises, or three years for higher-risk environments like factories or kitchens.

We also do a handover meeting. Ten minutes walking the site, showing you where isolators are, how to reset breakers, what the emergency lighting test button does. Sounds basic, but it saves panicked phone calls at 8pm when someone’s accidentally isolated the wrong board.

Post-Completion and Ongoing Compliance

The certificate isn’t the end. It’s the start of your compliance obligation.

You now need to maintain a log book, record any alterations, arrange periodic testing (every five years, or sooner if your insurer demands it), and test emergency lighting monthly with a full annual duration test. Portable appliances need PAT testing, frequency depends on the equipment type and environment, but typically annually for commercial offices and six-monthly for industrial or hire kit.

If you lease the building, your landlord will likely require proof of electrical compliance at rent review or lease renewal. If you’re in a regulated sector, care homes, schools, licensed premises, your regulator will ask for it during inspections. If you’re selling the business, the buyer’s solicitor will want to see it. That certificate you filed away? It’s a legal document.

We offer planned maintenance contracts covering periodic testing, emergency light checks, and reactive callouts. Not because we’re desperate for work, we’re busy enough, but because we’ve seen too many businesses caught short when a compliance deadline suddenly becomes urgent and every contractor’s booked solid.

What Slows Projects Down

Since we’re being honest: here’s what actually delays commercial electrical work.

Late decisions. You can’t finalise a lighting design if you haven’t chosen your ceiling tiles. You can’t order a panel if you haven’t confirmed your EV charger spec. Every day of indecision adds a day to the programme.

Access issues. The landlord’s contractor is still on site. The building’s occupied and you didn’t arrange out-of-hours access. The key holder’s on holiday. We can’t install what we can’t reach.

Concealed obstacles. We open a ceiling void and find asbestos lagging. We lift a floor and hit a water main that’s not on any drawing. We isolate a board and discover it’s feeding a circuit in the unit next door. Some of this is unavoidable. Most of it surfaces during a proper survey if the surveyor’s allowed to open things up.

Supply chain delays. Commodity kit, cable, accessories, standard panels, we hold in stock or can get next-day. Specialist gear, smart lighting controls, high-integrity panels, imported switchgear, can run weeks or months. We flag long-lead items at quotation stage, but only if you’ve actually specified what you want.

Scope creep without programme adjustment. You add three rooms to the fit-out but still expect the original completion date. Doesn’t work. More scope needs more time. We’ll squeeze where we can, but physics is physics.

Bottom Line

A commercial electrical project isn’t just “get a sparks in to wire it up.” It’s a structured process involving design, compliance, coordination, installation, testing, and certification. Each stage depends on the one before. Rush the design and you’ll pay for it in installation delays. Skip the testing and you’ll fail your inspection. Forget the certification and you’ve got no proof the work was ever done properly. The contractors who understand this deliver on time and on budget. The ones who don’t leave you with a half-finished job and a stack of problems. We’ve been doing this for 20 years across London and Essex. We know which category we’re in.