Typical 2026 rate
Architect-designed bespoke £3,500-£5,500/sqm UK average BCIS Q2 2026[BCIS Q2 2026]. London + premium-detailed projects regularly clear £6,500/sqm. The wide range reflects how much of the design is bespoke vs catalogue.
Passivhaus uplift
Certified Passivhaus targets 15 kWh/m2/yr space heating and 0.6 air changes/hour at 50 Pa. Achieving certification adds roughly £200-£400/sqm to a comparable mid-range build for the airtightness detailing, triple glazing, MVHR-with-summer-bypass, thermal-bridge-free junction detailing, and certification fees themselves. The Passivhaus Trust publishes case studies with cost data.
Contractor profile
A named main contractor with experience of bespoke joinery, complex glazing systems, and architect-quality detailing. Often the contractor brings the joiner, glazier, and roofer they have worked with before. Tender list short (3-5 contractors); price competition limited; quality control high. Contractor's preliminaries 12-18% of build cost typical (vs 8-10% on developer-spec).
When full Stage 4-6 architect pays off
Where the design has bespoke geometry, structural-glazing junctions, complex roof forms, statement staircases, or basement extensions. The architect's Stage 4-6 detailing typically costs 5-8% of build cost (on top of Stage 1-3 design fee) and saves materially more in construction errors and warranty defects. On a £1.2M architect-designed build that is £60k-£96k of fee against £150k-£250k of avoided rework risk.