Tonbridge & Malling Borough Council handles planning applications for most of the Tonbridge area. Standard PD rules apply — single-storey rear extension up to 4m (detached) or 3m (semi/terrace), within 4m height, is PD; Prior Approval covers up to 8m/6m. TMBC strongly recommends applying for a Lawful Development Certificate (LDC) on any project near the flood plain, a classified road or a conservation area, as it gives written confirmation of PD status. Two-storey extensions and side extensions need a full application. Note that Tunbridge Wells Borough Council handles the Tunbridge Wells side of the boundary — check which authority covers your property first.

The Party Wall etc. Act 1996 applies across Tonbridge. Notice is required when building on a shared wall, excavating within 3m of a neighbour's foundations to a depth beyond theirs, or excavating within 6m where a 45° line from the base of those foundations is undercut. Tonbridge's Weald Clay plots require deeper foundations than sandstone or chalk areas, meaning the 3m threshold is more commonly triggered even on modest rear extensions on town-centre terrace properties. On flood-zone frontages, piled foundation solutions further increase the likelihood of a notice being required. We assess party wall obligations at the site survey stage.

Tonbridge town centre and the Medway valley floor lie within Environment Agency flood zones 2 and 3, and extensions in those zones attract closer scrutiny from TMBC planners and the EA as a statutory consultee. Raising finished floor levels above the existing DPC — required by building regulations in flood zones — and specifying flood-resilient finishes are standard on valley-floor extensions. Conservation areas at the castle end of Tonbridge and in surrounding villages (Hadlow, Hildenborough, Yalding) carry Article 4 directions removing some PD rights. The Kent Downs National Landscape also clips the eastern edge of the borough near Ightham and Borough Green, where materials guidance is stricter. TMBC's LDC route gives written confirmation of the planning position and is worth obtaining before works start on any constrained plot.