Pre-construction phase: 6-9 months typical
The pre-construction phase dominates London new-build timelines and is frequently underestimated. Site acquisition due diligence (3-6 weeks): boundary survey, ground investigation including borehole survey on London clay sites, contamination report on brownfield, services and utilities desktop assessment, planning history review. Design (3-5 months): architect appointed, initial concept design (4-6 weeks), pre-application advice from borough (4-6 weeks), planning drawings package (6-8 weeks), structural engineer and services consultant integration. Planning decision (2-3 months): full planning application submission, 8-week statutory determination period (often extended to 10-12 weeks in inner London), conditions discharged before site start (4-6 weeks). Tender (4-6 weeks): contract documents prepared, three contractors tender, comparison and award. Contract signing and mobilisation (2-3 weeks). Total pre-construction 6-9 months is typical; faster only on tightly scoped sites with confident planning, slower with refusals, appeals or complex conservation considerations.
Construction phase: 12-18 months typical
Construction follows seven major phases. Phase 1, Site setup and demolition (2-4 weeks): hoarding, site huts, security, demolition of existing structure if applicable, waste disposal. Phase 2, Substructure (6-10 weeks): excavation, piled or raft foundations, ground beams, slab, ground floor build-up, drainage. Phase 3, Frame and envelope (12-16 weeks): timber, masonry or steel frame, roof structure, weatherproof envelope, windows and external doors installed. Phase 4, First fix (10-14 weeks): electrical, plumbing, heating, MVHR, insulation, plasterboard. Phase 5, Second fix (10-14 weeks): plaster finish, joinery, electrical and plumbing fittings, kitchen, bathrooms, flooring. Phase 6, External works (4-6 weeks, often overlapping): patios, driveways, fencing, soft landscaping. Phase 7, Snagging and Building Control sign-off (3-5 weeks): final inspections, defects rectification, Final Certificate, warranty inspection, handover. Total 12-18 months for 200-300m² home, 18-24 months for 350m²+ or split-level basement schemes.
Utility connections — the most variable phase
London utility connections are routinely the most schedule-disrupting phase of new-build delivery. Typical 2026 lead times: Thames Water mains water connection 8-16 weeks from application; SGN gas connection 12-20 weeks; UK Power Networks electrical connection 16-26 weeks for new substations (often required for any house over 23 kVA load on Future Homes Standard ASHP plus EV charging); Openreach broadband 4-8 weeks. Sewer connection via Thames Water 6-12 weeks for typical residential connections, 16-20 weeks where adoption of new sewer is needed. The critical path issue: lead times must be initiated 6-9 months before required completion date, but many builders only apply at the start of site works, creating a 4-12 week gap between practical completion and utility handover. Always apply for utilities at the planning approval stage, not at site mobilisation.
