Realistic UK loft conversion timeline: Velux 4–6 wks, dormer 6–10 wks, hip-to-gable 8–12 wks, mansard 10–14 wks — plus design, planning and party wall. This guide is written by PG Property Repairs and Renovations, an FMB and TrustMark accredited building company based in Worthing, using real costs and timescales from projects completed across Worthing, Lancing, Shoreham, Brighton and the wider West Sussex area.