Electrical Safety First's Best Practice Guide 4 and NICEIC's published EICR guidance agree on a short list of defects that account for most Unsatisfactory domestic reports, and the top two on any inspector's tally are missing 30 mA RCD protection and missing main protective bonding. Neither costs much to put right, and both are coded inconsistently across the trade, which is why landlords compare reports and ask why one electrician passed what another failed. This guide runs through the ten observations that most often make an EICR Unsatisfactory, with the code each usually attracts, the regulation that backs it, and a form of words that survives scrutiny.
- C1 (danger present), C2 (potentially dangerous) and FI make a report Unsatisfactory; C3 does not.
- The most common C2s are missing RCD protection and missing or undersized main bonding.
- Code by the risk in this installation, not the calendar: an older installation is compared against current BS 7671 to assess condition, not to force an upgrade.
- Write observations with the location, circuit, what was found and why it is a danger.
- The same defect can attract different codes in different circumstances; record the reasoning.
How are observations coded?
Before the list, the coding rule. BS 7671 Chapter 65 and IET Guidance Note 3 define the classification codes used on the EICR, and Best Practice Guide 4 (free from Electrical Safety First and endorsed by NICEIC, NAPIT, ECA and SELECT) gives the worked examples that most inspectors work from:
| Code | Meaning | Effect |
|---|---|---|
| C1 | Danger present. Risk of injury. Immediate remedial action required | Unsatisfactory |
| C2 | Potentially dangerous. Urgent remedial action required | Unsatisfactory |
| C3 | Improvement recommended | Satisfactory |
| FI | Further investigation required without delay | Unsatisfactory |
The principle in GN3 is that C1 is danger now (exposed live parts, incorrect polarity making metalwork live), C2 is danger under a foreseeable fault condition (no earth, so a fault would make metalwork live but nothing is live today), and C3 is a departure from current BS 7671 that does not create danger. See EICR observation codes explained: C1, C2, C3 and FI for the framework.
1. No 30 mA RCD protection for socket outlets
The most frequent C2 on pre-2008 installations. Regulation 411.3.3 requires 30 mA RCD protection for socket outlets rated up to 32 A. BPG4 codes the absence of it C2 where sockets may reasonably supply portable equipment outdoors (typically ground-floor sockets and any near an external door), and C3 for indoor sockets on an installation that pre-dates the 17th Edition where the risk is lower. Many inspectors treat all socket circuits with no RCD as C2 on a rented property, on the basis that the tenant's use cannot be controlled.
Sample wording: "Circuit 6 (ground floor sockets): no additional protection by 30 mA RCD. Sockets within reach of external doors and likely to supply equipment outdoors. C2."
2. No RCD protection for cables concealed in walls
Regulation 522.6.202 requires cables in walls at less than 50 mm depth, not in earthed metal containment or mechanically protected, to have 30 mA RCD protection. This catches nearly every domestic circuit in a plastered wall. BPG4 codes the absence as C3 in general, rising to C2 where the installation also has other shortcomings or the cables are in a location where damage is likely. In practice it is usually listed alongside item 1 and coded the same way.
3. No RCD protection in a bathroom
Section 701 requires 30 mA RCD protection for all circuits in a location containing a bath or shower (Regulation 701.411.3.3). An unprotected electric shower circuit, a lighting circuit feeding a fitting in zone 1 or 2, or a shaver socket circuit without an RCD is C2 under BPG4, and it is the defect most likely to cause a serious injury among the ten. See Bathroom Zones Explained: Section 701 of BS 7671.
4. Missing or undersized main protective bonding
Regulation 411.3.1.2 requires main protective bonding to extraneous-conductive-parts: incoming metal gas, water and oil services, structural steel and the like. Missing bonding to a metal gas or water service is C2 in BPG4 without much debate, because under an earth fault or a broken PEN the unbonded pipework sits at a different potential from the bonded metalwork next to it. Undersized bonding (6 mm² on a PME supply where 10 mm² is required by Table 54.8) is usually C3 if the conductor is sound and connected. Bonding that is present but disconnected at one end is treated as missing. The incoming service being plastic, with no metal pipework inside, means no bonding is needed and the inspector should say so. What is main protective bonding? Explained covers what needs bonding, and Earthing Arrangements Explained: TN-S, TN-C-S and TT covers the sizes.
Sample wording: "Main protective bonding to incoming metal water service not present (checked at stopcock and at MET). TN-C-S supply. C2."
5. No earth, or an ineffective earth, at the origin
An earthing conductor connected to a water pipe, a corroded lead sheath clamp with Ze off the scale, a TT installation with no rod, or an earth terminal at the cut-out with nothing connected. Under fault conditions every exposed-conductive-part becomes live, and the MCBs will not disconnect. BPG4 codes an absent or ineffective means of earthing C2, and C1 where an earth fault is present at the same time (metalwork already live). Confirm with a Ze measurement and inspection of the connection, and if the earthing type cannot be determined, FI.
6. Damaged, broken or missing accessories exposing live parts
A cracked socket front, a light switch with the rocker missing, a pendant with the cord grip gone and the conductors visible, a ceiling rose with the cover off. Anywhere a finger can reach a live part is C1. BPG4 is clear: exposed live conductors are the definition of danger present, and the inspector's duty is to make safe on the spot. Damaged accessories where the live parts remain enclosed (a chipped socket, a switch that is loose on the wall) are C2 or C3 depending on whether further deterioration is likely.
7. Incorrect polarity
Line and neutral reversed at a socket, a switch in the neutral rather than the line of a lighting circuit, or an Edison-screw lampholder with the line on the outer contact. Polarity errors that leave metalwork live or a lamp cap live with the switch off are C1. Reversed polarity at a socket where the appliance still works is C2 (an appliance with a single-pole switch or fuse is no longer protected). Polarity is a mandatory test on every circuit; see Polarity Testing Explained: Checks, Methods and EICR Codes.
8. Consumer unit defects: missing blanks, thermal damage, wrong device types
The board attracts several distinct observations. Missing blanking pieces leaving busbar or terminals accessible: C1 if a finger can touch live parts, C2 if only a tool could. Signs of overheating at terminals or on the busbar: C2, and worth a thermal check on the neutral bar. A rewirable fuse board in good condition: C3 on its own, though BPG4 notes it will usually be accompanied by items 1 to 3. A plastic enclosure in good condition: C3. Plastic enclosure with thermal damage or on a wooden staircase escape route with combustible material around it: C2. A type AC RCD protecting circuits with DC-producing loads: C3 with a note. The 2026 specification for a replacement is in RCBO vs RCD Split-Load Boards: Which to Fit and Why.
9. Undersized or unprotected circuits and cables
A 6 mm² shower circuit on a 50 A breaker; a 1.0 mm² lighting circuit on a 16 A MCB; a ring final with a 4 mm² spur feeding a hob; a socket circuit extended in flex; cable joints made with insulating tape or a chocolate block in the loft with no enclosure. Overcurrent protection that does not protect the cable is C2 (Regulation 433.1). Cables joined without a suitable enclosure are C2 where the joint is accessible or at risk, and C3 in an unlikely-to-be-disturbed loft where the joint is otherwise sound. Cable sizing against breaker ratings is in Cable Sizing and Volt Drop Basics: Ib, In, Iz and Table 4D5.
10. Borrowed neutrals, shared neutrals and circuits that cannot be isolated
The landing light fed from the upstairs circuit's line and the downstairs circuit's neutral is C2 in BPG4, because isolating one circuit leaves its neutral live. It comes to light when an RCBO board is fitted and shows up on an EICR by neutral-to-neutral insulation resistance testing with both circuits isolated. The full method is in Borrowed Neutrals: How to Find, Test and Code Them. Related isolation faults, such as a cooker switch that isolates the line only on a TT installation or a circuit fed from two consumer units, code the same way.
Which observations get coded inconsistently?
Three defects cause most arguments between inspectors, and most complaints from landlords who get a Satisfactory from one electrician and an Unsatisfactory from the next:
| Observation | Common wrong code | BPG4 position |
|---|---|---|
| Plastic consumer unit in good condition | C2 | C3 |
| No RCD on indoor socket circuit, older installation | C2 as a default | C3 unless outdoor use likely or other factors |
| 6 mm² main bonding on PME, sound and connected | C2 | C3 |
| No supplementary bonding in a bathroom with RCD protection and main bonding present | C2 | Not required (701.415.2); no code |
| Absence of circuit labels | C2 | C3 |
| No RCD on a lighting circuit | C2 | C3 (411.3.4 applies to new domestic circuits) |
Coding these C2 to generate remedial work is the practice that gives EICRs a bad name and that scheme assessors look for. Coding a genuine C2 down to keep a landlord happy is worse. The observation should state the reasoning so that another inspector can follow it.
How do you write the observation?
An observation needs the location, the circuit reference, what was found, why it is a danger and the code. GN3 says the report should be understandable by the person ordering it, who is usually not an electrician. Compare:
- "No RCD. C2."
- "Circuit 4 (kitchen ring final, 32 A type B): no additional protection by 30 mA RCD to Regulation 411.3.3. Sockets adjacent to sink and to rear door likely to supply equipment outdoors. C2. Recommend RCBO or RCD protection for this circuit."
The second version tells the landlord what to ask the next electrician for and tells the next electrician what was in the inspector's mind. How to Write EICR Observations That Stand Up has more examples, and Unsatisfactory EICR: What Happens Next (Landlords & Electricians) covers the remedial process and the certificate that closes the observations out.
How Certio helps
Certio produces the EICR, EIC, Minor Works certificate and PAT records on the BS 7671 model forms and turns them into branded PDFs. Photograph the consumer unit and the circuit schedule drafts itself; point the phone camera at a Megger MFT-X1 and the reading goes straight into the schedule of test results, or dictate it while your hands stay on the probes. Suggested observation wording with the regulation reference is there for you to check and confirm. The judgement stays yours; the typing goes. Starter is free for 7 days, then £5 a month.