The Landlord’s Electrical Playbook, Part 2 of 6
C1, C2, C3, FI — What Your EICR Codes Actually Mean
By Frankie · April 2026 · 8 min read
I handed over an EICR last week to a landlord in Fulford. Three C2 codes, one C3, and an FI. His first question was the same one I always get: “What do these letters actually mean, and how worried should I be?”
The codes on an EICR aren’t arbitrary. Each one carries a specific meaning, a specific level of urgency, and, for landlords, a specific legal obligation. But nobody explains them properly on the report itself, so here’s what they mean in plain English, with real examples from jobs I’ve carried out in York.
C1 — Danger Present
A C1 code means there is an immediate risk to anyone using the electrical installation. This is the most serious classification, and it’s rare, but when I find one, the defect needs to be made safe before I leave the property.
What it looks like in practice. On a property in Acomb last year, I opened the consumer unit and found a live conductor with no terminal connection, bare copper, energised, sitting loose inside the enclosure. Anyone who opened that consumer unit to reset a tripped breaker could have touched it. That’s a C1. I made it safe on the spot before continuing the inspection.
Other examples I’ve recorded as C1 in York properties: a missing blanking plate on a consumer unit exposing live busbars, a damaged socket with cracked faceplate where live parts were accessible, and a cable with severely degraded insulation running through a loft hatch opening where it was regularly disturbed.
C1, what it requires
Immediate action. The electrician should make the defect safe during the inspection, either by isolating the affected circuit, making a temporary repair, or disconnecting the hazard. The full remedial work must then be completed as soon as possible. For landlords, this means arranging the permanent fix without delay, the 28-day deadline still applies, but with C1 defects, waiting 28 days is not appropriate.
C2 — Potentially Dangerous
A C2 code means a defect that isn’t immediately dangerous but could become so under fault conditions or over time. This is the most common code that causes an EICR to be marked “unsatisfactory”, and it’s the one that triggers the 28-day remedial deadline for landlords.
What it looks like in practice. The most frequent C2 I record in York is lack of RCD protection on socket circuits. On older installations, particularly 1970s and 1980s houses across areas like Heworth, Clifton, and Huntington, the consumer unit predates RCD protection entirely. The circuits work. The lights come on. But if a fault develops, there’s no device to cut the supply before someone gets a shock. It’s not dangerous right now, but it’s potentially dangerous if a fault occurs.
Other C2 examples from recent York jobs: an earthing conductor undersized for the supply (common on older installations that were connected to a new supply without upgrading the earthing), inadequate bonding to gas and water services, and circuits protected by the wrong size overcurrent device, a 32A MCB on a circuit wired in 1.5mm cable, for instance.
C2, what it requires
Remedial work within 28 days. Under the Electrical Safety Standards Regulations 2020, landlords must complete all C2 remedial work within 28 days of the report date. A qualified electrician must carry out the work and provide written confirmation. That confirmation must then be supplied to the tenant and the local authority (if involved). Failing to meet this deadline is a breach that can result in a civil penalty of up to £40,000. Read more in The £40,000 EICR Fine, What Every York Landlord Needs to Know.
C3 — Improvement Recommended
A C3 code means the installation doesn’t meet the current edition of the wiring regulations but isn’t dangerous. It’s a recommendation, not a requirement, and critically, C3 codes alone do not make the EICR “unsatisfactory”.
But here’s what most landlords get wrong: they read “improvement recommended” and hear “optional”. It isn’t, not really.
What it looks like in practice. The most common C3 I record is the absence of surge protection, an SPD. The current wiring regulations (BS 7671:2018+A4:2026) require surge protection in most domestic installations, but an older installation that was compliant when it was installed won’t have one. It’s not dangerous, but it doesn’t meet today’s standard.
Other C3 examples: lack of additional protection (30mA RCD) on lighting circuits where now required, a consumer unit without individual RCBOs where they’d be beneficial, or cable routes that don’t comply with current safe zones but were acceptable under the regulations at the time of installation.
Why C3 doesn’t mean “ignore it”
Standards evolve. What’s a C3 today could become a C2 at the next inspection if the regulations tighten further. Addressing C3 items while a C2 remedial visit is already booked is often the most cost-effective approach, the electrician is already on site, the circuits are already isolated, and the incremental cost of fitting an SPD or upgrading a bonding connection during that visit is significantly less than a separate callout later.
FI — Further Investigation Required
FI isn’t a severity code like the others. It means the electrician identified something during the inspection that couldn’t be fully assessed and needs further investigation before a definitive classification can be given.
What it looks like in practice. On a Victorian terrace in Bishophill, I was testing the insulation resistance on a lighting circuit and got readings that suggested a partial breakdown, but the circuit ran through a floor void I couldn’t access without lifting floorboards. The readings weren’t bad enough to classify as C2 on the spot, but they weren’t clean either. I recorded FI because the only honest thing to do was flag it for further investigation rather than guess.
Other FI situations: circuits that couldn’t be isolated because the tenant had medical equipment that needed continuous power, restricted access behind fixed kitchen units where cables were routed, and readings that were borderline and needed repeat testing under different conditions.
FI, what happens next
An FI code means the inspection is incomplete for that item. The electrician needs to return to carry out the further investigation, which might involve gaining access to concealed areas, arranging for circuits to be de-energised when the property is unoccupied, or carrying out specialist testing. Until the FI is resolved, the overall EICR outcome may remain “unsatisfactory” or the report may note that certain areas were not fully assessed.
How to Read the Report
An EICR has several sections, but for landlords, the two that matter most are the overall assessment and the observations table.
The overall assessment is a single line near the top of the report: either “satisfactory” or “unsatisfactory”. If it says unsatisfactory, there are C1 or C2 codes in the observations. If it says satisfactory, there may still be C3 codes and recommendations, don’t skip past them.
The observations table lists every finding. Each row has the code (C1, C2, C3, or FI), a description of the defect, and the circuit or location affected. This is the section to focus on. If you’re not sure what an observation means, ask the electrician who wrote it, a good electrician will walk you through every line.
The rest of the report, the test results, circuit schedules, and supply characteristics, is technical data that the electrician uses to support the findings. You don’t need to interpret those figures yourself, but they should be complete. If large sections are blank or marked “N/A”, that’s worth questioning.
What This Means for Landlords
If your EICR comes back satisfactory with no codes at all, you’re in the clear until the next inspection is due. Keep the report, give a copy to the tenant, and file it.
If it comes back satisfactory with C3 codes, you’re legally compliant but there are improvements worth considering. I’d recommend addressing them at the next convenient opportunity, particularly if a consumer unit upgrade is on the horizon anyway.
If it comes back unsatisfactory, you have 28 days to get the C1 and C2 defects remedied. Don’t wait. Book the work, get the written confirmation, and send a copy to the tenant. If you need a second opinion on what’s been flagged, that’s a legitimate reason to bring in another qualified electrician, I offer second-opinion inspections for exactly that purpose.
Frankie Sewell
NICEIC Approved Contractor • YRLA Recognised Service Provider • Bright Sparks of York
Need an EICR explained or a second opinion?
I carry out EICRs across York and can walk you through every code on the report. If you’ve had an EICR done elsewhere and aren’t sure about the findings, I offer second-opinion inspections.
The Landlord’s Electrical Playbook, Part 2 of 6 · All parts →