Costs & Timelines

A 45sqm rear extension sounds simple—until you meet pre-application fees, the Planning Portal charge, condition discharge costs and the sometimes-scary Community Infrastructure Levy (CIL). We priced the same scheme across Islington, Waltham Forest and Wyre Forest to show how council-side costs stack up—and how a single CIL exemption form can save £10k–£50k+ if you go bigger.