Electrical design for tenant renovations

Electrical design for a tenant renovation starts with two questions: what does the tenant need, and what can the building give them? The answer depends on spare capacity in the floor's panels, the transformer and feeder that serve them and, for large loads, the building's service. Once capacity is confirmed, the design covers new power and lighting, changes to fire alarm and emergency lighting, the demolition of old wiring and the records that keep the building's drawings accurate for the next tenant.

Tenant fit-outs are where most of a commercial building's electrical history is written. Each one adds circuits, moves devices and leaves its own layer of changes. Done well, a fit-out leaves the building with up-to-date panel schedules and spare capacity still known. Done poorly, it leaves abandoned wiring in the ceiling, panels with no spare spaces and nobody sure what is fed from where.

Start with the lease and the base building

The lease usually sets out what the landlord provides and what the tenant pays for. Many commercial leases define an electrical allowance, such as a certain capacity per unit of floor area, and spell out who pays for anything beyond it. They may also require the tenant to use the landlord's engineer or to have the design reviewed by them, and set rules for shutdowns and after-hours work. Read these clauses before design starts; they decide who pays for a new panel or a larger transformer.

The base building is everything outside the tenant's space that serves it: the electrical room, the riser, the transformer, the main switchboard and shared systems like the fire alarm. Changes to the base building usually need the landlord's approval and may be done by the landlord's contractors.

Checking capacity at every level

A new load does not just need a spare breaker. It adds to every piece of equipment between the tenant's space and the utility. The design checks each level in turn: the panel on the floor, the transformer that feeds it, the feeder or riser, and, for larger loads, the main switchboard and the service.

For an ordinary office fit-out, the floor panel and transformer are usually the limits. Restaurants, labs, medical clinics, server rooms and fitness studios add heavy loads that can reach further upstream. Measured demand data from the building and the tenant's equipment list make the check far more reliable than guessing from breaker sizes.

What the design covers

• Demolition and make-safe. Removing abandoned wiring back to its source, not just cutting it at the ceiling, and updating panel schedules.
• Power. Receptacles, dedicated circuits for equipment, workstation feeds, kitchen and server room power.
• Lighting and controls. New layouts and the automatic controls the energy code adopted in your province may require when lighting is replaced.
• Emergency lighting and exit signs. New walls change exit routes, so coverage is checked against the new layout.
• Fire alarm. Devices added or moved for the new layout, coordinated with the base building system and its contractor.
• Mechanical connections. Power for new or relocated HVAC units, exhaust fans and controls.
• Communications. Pathways and power for cabling, WiFi access points and AV, coordinated with the low-voltage designer.

What to gather before design starts

• The lease clauses on electrical capacity, approvals, contractors and shutdowns.
• The landlord's fit-out guidelines, if they have them.
• Base building drawings: single-line diagram, floor electrical plans and panel schedules.
• A list of the tenant's equipment with nameplate ratings or manufacturer data.
• The furniture layout, which drives receptacle and workstation power.
• Hours of operation and any loads that must stay on during outages.
• Contact details for the base building fire alarm contractor.

Gaps in this list are normal, and the site survey fills many of them. The equipment list is the one item that is hard to replace, so ask the tenant for it early, even in draft.

How a fit-out project usually runs

1. Brief and lease review. The tenant's needs, equipment list, schedule and the lease's electrical clauses.
2. Site survey. Panels, transformer, spare capacity, existing devices, ceiling space and what can be reused.
3. Design. Drawings and specifications, coordinated with the architect, mechanical designer and the landlord. Drawings for permit are sealed by a licensed professional engineer where required.
4. Landlord review and permit. The landlord or their engineer reviews the design; the contractor takes out the electrical permit.
5. Construction. Installation by a licensed electrical contractor under permit, with shutdowns scheduled to suit other tenants.
6. Close-out. Inspections, fire alarm verification, updated panel schedules and record drawings delivered to both tenant and landlord.

Common mistakes

A typical case

A dental clinic is leasing a former office suite. Its equipment list includes compressors, vacuum pumps, sterilisers and imaging equipment, plus more lighting than the office had. The survey shows the floor panel has a few spare spaces, but the transformer feeding it is already well loaded by the neighbouring tenants. The design adds a new sub-panel for the clinic fed from a spare breaker in the electrical room's distribution panel, which is served by a feeder with capacity to spare, bypassing the busy transformer. The imaging equipment's own electrical requirements come from the manufacturer and are designed in from the start. New walls mean new emergency lighting coverage and relocated fire alarm devices, verified before opening. At close-out, the panel schedules on the floor and in the electrical room are updated, and the landlord receives drawings showing the new sub-panel and its feed.

How ehZee can help

We design fit-out electrical work for tenants and landlords, including capacity checks and base building reviews. See our electrical design service, and read receptacle and circuit planning and inspecting a commercial space before you lease.

Common questions