Understanding the electrical diagnosis and what's at stake on site
What an electrical diagnosis covers: essential check points
The electrical diagnosis checks the state of the indoor installation on safety points. The inspector checks in particular for the presence of a main cut-off device, overcurrent protection, at least one 30 mA residual current device, earthing and equipotential bonding. It also spots outdated or unsuitable equipment and poorly protected conductors. The goal is simple: identify the risks of electric shock and fire before starting a job.
When the diagnosis is mandatory and for which homes
It's required for sales and rentals when the installation is over 15 years old. It applies to homes, houses or flats, and is included in the property survey file. On site, this helps you frame the works and price the electrical package. You know what falls under a simple repair, and what requires an immediate safety fix.
Difference between diagnosis, inspection and safety fix: avoiding confusion
The diagnosis describes and flags anomalies. It doesn't validate overall compliance. An inspection, on the other hand, can be carried out after works to check what's been done. The safety fix corresponds to the minimum actions needed to remove the hazards (residual current protection, earthing, accessible cut-off). Think of it like a warning light. The diagnosis switches on the alert, your works restore the light.
The most common electrical risks and how to spot them
Electrical panel, protection and earthing: the warning signs
An old panel (fuse holders, no 30 mA residual current breaker), circuit breakers tripping for no reason, or sockets without an earth pin are classic signals. Also look for scorch marks, a burning smell, or an open enclosure. An electrical diagnosis checks earth continuity and whether the protection is suitable.
Equipotential bonding and wet rooms: risk areas
In a bathroom, the absence of equipotential bonding, appliances too close to the shower, or unprotected sockets increase the risk of electric shock. Simple clues: exposed wires, cracked enclosures, and the presence of water near connections. Have the zones and residual current protection checked.
Cabling, sockets and fittings: signs of an ageing installation
Damaged conduits, fabric-covered cables, sockets that get hot, sparks on plugging in, or switches that crackle often indicate ageing. If you see wire nuts outside a junction box or permanent extension leads, the fire risk climbs fast. A targeted check secures things without redoing everything.
On-site method for a reliable, usable diagnosis
Preparing the visit: documents, questions for the client and quick surveys
Before starting the diagnosis, ask for the EPC, energy bills, floor plans, and any recent report (a retrofit assessment, boiler service, mechanical ventilation). Ask simple questions about comfort, cold rooms, damp, usage, and works already done. On arrival, do a quick walkthrough. Spot the access points (loft, crawl space), air inlets, and sensitive points. Keep the essentials within reach.
Following a safety checklist: measurements, tests and observations
Apply a single checklist. PPE, electricity, gas, traces of mould, signs of asbestos or lead if the building is old. Measure temperature and humidity, check the draw of the flues, and observe the ventilation. A useful diagnosis starts with safety first.
Formalising your findings: photos, sketches and severity level
Photograph the defects and their context, then make a simple sketch of the surfaces and networks. Classify each finding by severity: urgent, to be treated, to be monitored, with a probable cause and an action. Your report becomes photo evidence, and so usable on site.
Securing your interventions after the diagnosis: priority actions
Immediate safety fix: what you can do without delay
After a diagnosis that reveals a risk, start by cutting the power supply concerned (electricity, gas, water). Isolate the area, take the equipment out of service, and inform the client in writing that use is prohibited until the fault is fixed. Take dated photos and note the precautionary measures taken.
Planning the compliance works: costing, phasing and coordinating the trades
Turn the diagnosis into an action plan. Draw up clear costing by item, with options if needed. Phase the works according to dependencies (ventilation before insulation, electrical before finishes). Coordinate the trades and the checks, especially if a compliance certificate is required at the end of the job.
Tracing and getting sign-off: reports, certificates and the tradesperson's liability
Formalise everything. A signed report of the safety fix and handover limits grey areas. Keep quotes, amendments, technical data sheets, manuals, and proof of settings. For certain modifications, plan for the appropriate certificate (Consuel for electricity, gas compliance certificate). On liability, clearly explain what you've fixed, and what's still to be treated.
Diagnosis in 2026: requirements, aid and good practice to stay compliant
Rules and references to know in 2026: what impacts your jobs
In 2026, a serious diagnosis before works secures your quotes and your funding applications. On the electrical side, BS 7671 and Part P remain the reference for safety fixes, with the EICR as the report that records the property's condition. On the retrofit side, the funding files require solid proof. EPC, retrofit assessment if required, detailed invoices, photos, and traceable registration. To anticipate changes, rely on the new EPC rules in 2026.
Energy retrofit cases: heat pump, mechanical ventilation, EV charging and electrical sizing
A heat pump, a high-performance mechanical ventilation system or an EV charging point change things at the panel. Check the subscribed power, the state of the protection, the earthing, and circuit balancing. Proper sizing avoids nuisance tripping and extends lifespan. For EV charging, follow the regulatory framework and the appropriate qualification.
Advising the client on safety: simple, educational arguments
Explain it simply. It's not just about "bringing it up to standard". You're reducing the risk of overheating and fire, stabilising comfort, and preparing for new electrical uses. Propose a prioritised safety fix, then the optimisations. Your diagnosis becomes a clear action plan, like a light guiding the job.
