Skip to content
ProjectsCost GuidesGuidesAnswersInsightsAbout
Get a Quote

Quick Answer

Design and Build vs Traditional Contract for a London Renovation?

Design and Build (D&B) contracts in London give the contractor responsibility for both design and construction — single point of accountability, faster programme, lower client design fees. Traditional contracts separate architect (design) from contractor (build) — better design quality, more client control, longer programme. D&B suits commercial scale and replicating designs; traditional suits bespoke residential and listed property.

Full House Renovations →Get a Free Quote
01

Traditional contract structure

Architect designs (RIBA Stages 1–4); produces tender drawings and specification; contractors tender competitively; client awards contract; contractor builds to architect's design; architect administers contract (site visits, payment certification, variation control); architect signs off completion. Client pays: architect 8–12% of construction cost; QS 2–3%; contractor 80–85%. Total professional fees ~12–17%. Risk: design risk with architect (PII); construction risk with contractor (PII + warranty); client retains client risk (changing brief, late approvals).

02

Design and Build structure

Contractor takes responsibility for both design and construction. Client provides Employer's Requirements (brief, performance standards, key parameters); contractor provides Contractor's Proposals (detailed design + price); single contract concept to completion. Architect: novated to contractor (engaged by client, transferred to contractor at construction start) — common; or independent architect on client side overseeing. Client pays: minimal design fee at brief (Employer's Requirements ~2–4%); contractor inclusive of design (~90–95%); independent monitoring 1–2%. Total fees ~7–12% — lower than traditional.

03

Risk allocation differences

Traditional: design risk with architect → if design fails, architect's PII pays. Client controls design quality. Contractor risk limited to building per design. D&B: design + construction risk both with contractor → single point of accountability. If anything fails, contractor responsible. Client has less control over design detail. Contractor incentivised to minimise cost — design quality may slip. Trade-off: less risk to client (single point) vs less control. D&B works best with detailed Employer's Requirements + monitoring surveyor.

04

When each suits

Traditional suits: bespoke residential design, listed buildings, conservation areas, period restoration, where design quality and heritage detail matter. Example: Grade II Georgian terrace restoration — traditional with architect leading design and conservation consultant. Higher fees but bespoke high-quality outcome. D&B suits: cost-driven projects with standard specifications, multi-unit conversions, projects where time-to-completion matters more than design refinement.

More questions

Related questions answered.

Full House Renovations full guide →

Which is cheaper?

+

D&B typically 5–10% lower total: lower design fees, faster programme reducing client borrowing cost. But: design quality lower in D&B; resale and aesthetic value sometimes lower. For most London residential bespoke renovations, traditional contract delivers better value despite higher upfront fees.

Can I novate my architect to D&B?

+

Yes — common 'novated architect' D&B variation. Client engages architect for design (RIBA Stages 1–3); at construction start architect novates to contractor; same designer continues construction. Retains design quality; gives contractor single-point accountability. Slightly more expensive than pure D&B but combines advantages.

Is JCT Standard Building Contract D&B or traditional?

+

JCT has both. JCT Standard Building Contract with Design (SBC/D): D&B variant. JCT Standard Building Contract (SBC): traditional with architect's design. JCT Design and Build Contract: pure D&B. JCT Minor Works Building Contract: traditional, small projects. JCT Intermediate: mid-range, traditional.

Do D&B contractors deliver good design?

+

Variable. Premier D&B (Morgan Sindall residential, Mace, Multiplex residential) deliver excellent design via in-house architects. Mid-market D&B: acceptable standard residential. Smaller D&B builders: functional but may lack refinement. For bespoke high-quality residential, prefer traditional or novated D&B.

Ready to get started?

Senior consultant call within one business hour. Free desk-based planning assessment. Fixed-scope quote — no provisional sums, no day-rate creep.