retrofitcost.co.ukA surveyor's working file. Q3 2026 Ofgem cap applied.
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Working file A1

Victorian solid wall retrofit cost (UK 2026)

Victorian solid wall retrofit cost: working capex envelope, sequenced measure cost, PAS 2035 risk path.

Working envelope (95 m² mid-terrace)

Phased deep retrofit envelope: £42,000to£68,000(pre-grant). Net after BUS plus 0% VAT: £32,000to£58,000.

What drives the spread

  • IWI rather than EWI in most conservation areas (slimmer scope for thermal-bridge risk).
  • Sash window restoration vs slim double glazing vs full timber triple.
  • Suspended-timber-floor access (lift floorboards vs crawl space).
  • Path B or C under PAS 2035 with a Retrofit Designer engaged.

Risk path

ASHPMVHRU 0.18 W/m²KU 0.15 roofU 0.18 wallU 0.22 floorPath C, traditional construction

Heritage notes

BS 7913 and Historic England guidance are the references; breathability and hygrothermal performance lead the design conversation, not U-values alone.

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 A1]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.