BS 7671 Amendment 4 (2026): What Changes for London Landlords

BS 7671:2018 Amendment 4 was published April 2026 and applies to all new electrical work from October 2026. Existing installations are not retroactively required to comply — but EICR coding will reflect the new standards from October.

Type AC RCDs only detect AC fault current. Modern appliances (induction hobs, EV chargers, certain LED drivers) create DC components that Type AC cannot reliably detect. Amendment 4 makes Type A protection mandatory where DC fault current is foreseeable.

For most domestic boards this means an upgrade at the next replacement cycle. We're already coding Type AC C3 (improvement recommended) for AC-only boards installed before the DC-load appliances arrived.

AFDDs detect series arc faults caused by damaged cables or loose terminations — a common cause of electrical fires. Amendment 4 makes AFDD mandatory on socket circuits in higher-risk premises: HMOs, residential care, schools.

For new fuse-board upgrades in HMOs, we now include AFDD as standard. For existing installations, the change is gradual — code C3 on AFDD-absent circuits at next EICR.

SPD is required on installations supplied via overhead lines, and recommended for installations with sensitive equipment. Most London installations are underground-fed, so SPD is recommended (C3) rather than mandatory — but with EV chargers and home batteries proliferating, we install SPD by default on board upgrades.

For most landlords this is a fuse-board upgrade question, not an immediate cost. Expect Type A RCBO + SPD + AFDD to add ~£150 to a standard board change versus the previous Type AC + RCD-only spec. £750 all-in for a 6–12 way board is the current market price for an A4:2026-compliant installation.