retrofitcost.co.ukA surveyor's working file. Q3 2026 Ofgem cap applied.
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Working file A3

1960s system-built house retrofit cost (UK 2026)

1960s system-built house retrofit cost: working capex envelope, sequenced measure cost, PAS 2035 risk path.

Working envelope (80 m² system-built)

Phased deep retrofit: £48,000to£75,000(pre-grant). Net after BUS: £40,000to£67,000. The system-built premium is real and reflects survey, design and Path C fee uplift.

Construction types

  • No-fines (Wimpey No-Fines): EWI works once thermal-bridging is detailed.
  • BISF: steel frame; EWI plus careful detailing of cold bridges.
  • Concrete panel (Reema, Cornish Unit): valuation and mortgageability often the lead concern.

Risk path

ASHPMVHRU 0.18 W/m²KU 0.15 roofU 0.18 wallU 0.22 floorPath C, system-built
Surveyed 22 June 2026. Ofgem Q3 2026 cap applied (gas 7.33p, elec 26.11p, gas standing 29.04p). Next scheduled review 26 September 2026 (Q4 cap publication). [ref A3]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.