The five main types of loft conversion compared: Velux, dormer, L-shaped dormer, hip-to-gable and mansard. Headroom needed, 2026 costs, planning rules and which suits your house. 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.