Do you need planning permission to convert a garage? 2026 UK rules on permitted development, conservation areas, flats, building regs and lawful development certificates. 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.