Commercial fit out: what does the electrical contractor need from you?

What is the difference between a CAT A and a CAT B fit out, electrically?

CAT A is what the landlord provides to make the floor lettable. CAT B is what the tenant adds to make it theirs, and that is where most of the electrical work on a fit out sits.

A typical CAT A shell has an incoming supply and a landlord’s board, basic lighting to an open floor, and the base fire alarm and emergency lighting. Nothing on it is where the tenant will want it.

CAT B is partitions, meeting rooms, a tea point, the desk layout, the comms room, and the lighting that follows the new rooms. Every one of those has a cable in it, so the electrical package is mostly CAT B, designed round a shell somebody else built.

Do we need the landlord’s permission before the electrician starts?

Almost always, yes. A commercial lease normally forbids alterations without the landlord’s written consent, and the document that gives it is a licence to alter.

The law says a landlord cannot unreasonably withhold consent to improvements, but it does not say they have to be quick, and the licence is where the conditions live: cable and containment types, where you may not fix, drawings reviewed by the landlord’s consultant, copies of every certificate, and what must be reinstated at lease end.

Start the licence the day the design is agreed. Send us the draft with the drawings and we will price to its conditions rather than discover them in week two.

What does the electrician check in the shell before pricing?

The supply, the board, the metering and the condition of what is already there. A quote written without seeing them is a guess.

• Supply capacity. What the landlord has allocated to the demise, single or three phase, and whether it will carry the kit. Our three phase article covers it.
• The landlord’s board. Spare ways, protective devices, where the tenant’s submain lands, and whether a new board for the demise is the cleaner answer.
• Metering. Whether the demise is separately metered. Sub-metering is often a licence condition and it goes in at first fix, not afterwards.
• The existing installation. A condition report on what CAT A left says whether the lighting and containment can be reused. Reuse is cheaper only if it tests clean.
• The routes. Floor depth, ceiling void, risers, and what already occupies them.

As an occupier you take on a standing duty under the Electricity at Work Regulations for the system in your premises the day you move in, so what the shell contains is your problem too.

What does the electrician need to know about the tenant’s kit?

Everything with a plug or a cable, before first fix, on a drawing. The layout is the gate on a fit out just as it is on a house build, and the list is longer than people expect.

Desks and how they get power: floor boxes, power poles or perimeter trunking, with data or without. The tea point or kitchen. The comms room and its cooling. Air conditioning, which is normally the mechanical contractor’s kit on our supply, so the loads are agreed between the two trades. Signage, EPOS, access control, CCTV, screens, EV charge points outside.

Lighting gets decided last and should be decided first. Under Part L of the Building Regulations, new lighting in a non-domestic building has to meet efficacy and control requirements, which in practice means LED with occupancy or daylight control in most rooms. The layout follows the partitions, so it cannot be fixed until the room plan is.

How does the electrical work fit the fit out programme?

First fix goes in once partitions are framed and before they are boarded, second fix after decoration, and testing sits on the programme as its own item. That much is the same as any build, and our first and second fix article covers it.

What is different on a fit out is the building around you. The floor below is trading, the riser is shared, and the isolation you need to connect the submain takes the neighbouring tenant off too. Isolations are agreed with the managing agent in advance, usually out of hours, and a programme that has not allowed for that has a gap in it. Live premises are normal for us.

CDM 2015 applies to fit outs like any other construction work. The principal contractor plans and coordinates, and every contractor, including us, has duties to plan and manage its own work. RAMS come as standard.

Who does the fire alarm and emergency lighting on a fit out?

A fire specialist, not us, and we say so at the start rather than including it and hoping.

A fit out changes escape routes. New partitions, rooms and doors mean the emergency lighting and detection designed for the open CAT A floor no longer match the building, and the responsible person under the Fire Safety Order has to have a system that suits the premises as they now are. That is a design question answered against the fire strategy, then installed, commissioned and certified by people who do that work all day.

Here is the honest bit. Plenty of electrical contractors put a line for emergency lighting in a fit out package because it wins the job. What the tenant gets is fittings on a circuit with no design behind them and a certificate that does not say what the fire officer or the insurer will ask for. We install the containment and supplies the fire contractor needs and leave the design and certification to them. If that costs us the odd package, so be it.

What should the handover pack contain, and does building control need to know?

An Electrical Installation Certificate for the new work, with the test results and a board schedule that matches the labels. As-installed drawings, because the design drawing never survives the ceiling void. Commissioning records for the lighting controls. An operation and maintenance pack where the contract asks for one. And the copies the licence says the landlord gets.

Building control is separate. Electrical work in a commercial building is not notifiable under Part P, which only covers dwellings, but the fit out as a whole may need building regulations approval for the partitions, fire precautions, ventilation and Part L lighting, and the electrical certificate is part of the evidence at completion. The fit out contractor usually holds that application. Our paperwork is ready when it is asked for.

What changes the price of a fit out electrical package?

We price from drawings, the licence and the shell survey, not a rate per square foot.

• The point count and the desk power method: floor boxes and power poles are different jobs.
• Whether the landlord’s board and supply can take the load, or a new board and submain are needed.
• How much of the CAT A lighting and containment can honestly be reused.
• The licence conditions: specified cable types, restricted fixing, reinstatement at lease end.
• Out of hours working and the number of isolations the building needs.
• The kit: a kitchen, a comms room, air conditioning, EV charging.

Send the drawings, the draft licence and your programme through our quote page, or see how we run commercial fit outs first. We will tell you what the shell can take before we tell you a number.

Questions we get asked about this