No, a plastic consumer unit does not automatically fail an EICR. In most homes it is recorded as a C3, “improvement recommended,” which does not make the report unsatisfactory. It only becomes a fail (a C2) in specific situations, such as signs of overheating or a board fitted after 2016 where the metal rule already applied.
Why do people think a plastic board fails?
The confusion comes from a genuine change in the regulations. Since 1 January 2016, a new domestic consumer unit has had to be made from non-combustible material, in practice a steel (metal) enclosure. The rule started as Amendment 3 to the 17th Edition wiring regulations and has carried forward into the current 18th Edition under regulation 421.1.201. The idea is simple: if a loose or poorly made connection ever overheats inside the board, a metal enclosure helps contain any fire rather than letting it spread.
Because every new board now has to be metal, a lot of people assume an older plastic one must be illegal or must fail an inspection. It does not. The 2016 rule applies to new installations and replacements, not retrospectively to every plastic board already on a wall.
So how is a plastic consumer unit coded on an EICR?
An EICR grades each issue with a code, and only certain codes cause a fail:
- C1 — danger present. Immediate risk.
- C2 — potentially dangerous. This is what makes a report unsatisfactory.
- C3 — improvement recommended. Safe, but below the current standard. Does not fail the report.
- FI — further investigation required. Also makes a report unsatisfactory.
A sound, undamaged plastic board that was compliant when it was installed normally gets a C3. It is doing its job safely; it simply would not be allowed if you were fitting a board today. A report can be fully satisfactory with a C3 on it, which means a plastic consumer unit on its own does not stop your property passing. If you want the codes explained in full, see our guide to EICR C1, C2 and C3 codes.
When does a plastic board become a C2 fail?
There are real situations where a plastic enclosure is escalated to a C2 and does cause a fail. An honest electrician codes on what is actually in front of them, not a blanket rule. The common ones are:
- Signs of heat damage. Browning, scorch marks, melting, a burning smell or distortion around the fuse holders. That is no longer “improvement recommended,” it is potentially dangerous now.
- Location under a timber escape route. A combustible board sitting under wooden stairs that form the only way out of the property raises the fire risk and is often coded more seriously.
- A board fitted after January 2016 in plastic. If a plastic board was installed once the metal rule was already in force, it was non-compliant from day one and is coded accordingly.
- Other faults stacking up. Often the plastic enclosure is the least of it. The same old board frequently has no RCD protection, which is a separate C2 in its own right.
That last point matters most. Plenty of plastic boards that get replaced are not replaced because they are plastic, they are replaced because they offer no modern shock protection, and that is the real fail.
Does the age of the board change things?
Yes, indirectly. A plastic board fitted in, say, 2014 is usually a tidy unit with RCDs and is coded C3 for the enclosure alone. A plastic board from the 1990s is a different animal, it often has rewireable fuses, no RCD, and tired connections, so it tends to collect several C2 codes regardless of what the enclosure is made of. In that case the plastic is almost beside the point. You can read the wider signs a fuse board needs replacing to see what else gets flagged.
Should I upgrade to a metal board anyway?
If your plastic board is sound, you are not obliged to change it, and we will tell you that honestly rather than invent a reason to sell you a new one. A C3 is a recommendation, not a requirement. That said, there are good reasons people choose to upgrade: a modern metal board with individual RCBO protection on each circuit is safer, contains a fault better, and means one tripped circuit no longer plunges the whole house into darkness. If you are also adding an EV charger or doing other work, it is often the sensible moment to do it.
Snelling Electrical fits modern 18th-edition metal consumer units with full RCBO protection from £700, tested, certified and notified to building control, usually in a single day. We assess your existing board honestly first on the fuse board upgrade page, and if it does not need doing, you will be told so.