Permitted Development changes affecting London homes in 2026

The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 came into force on 1 September 2025 with effects continuing through 2026. The amendments tightened several rights in conservation areas and Article 4 zones while modestly expanding others outside those zones.

London is disproportionately affected because over 25% of London residential land is in a conservation area and a further 8% is under Article 4 directions. Most of central and inner London (Westminster, Camden, Hackney, Islington, Kensington and Chelsea, Hammersmith and Fulham, much of Wandsworth and Lambeth) is in one or both categories.

Outside conservation areas and Article 4 zones: the depth allowance under prior approval (Class A2) was confirmed at 6m for semi/terrace and 8m for detached, but new neighbour consultation procedures require 28 days for objections (up from 21 days previously). This pushes the prior approval timeline to roughly 7–8 weeks total.

Inside conservation areas: rear extensions now require full planning where they project more than 3m from the rear wall, even where they would otherwise qualify under prior approval. This is a tightening from the previous position where prior approval applied in conservation areas. Practical impact: many rear extensions in inner London now need full planning, adding 8–10 weeks to the timeline and reducing the rate of approval.

Inside Article 4 zones with specific roof-extension restrictions: the 2025 amendment confirmed that local authorities can restrict rear extensions as well as roof additions in Article 4 areas, formalising existing practice. This particularly affects Hackney, Islington and parts of Lambeth.

The 40m³ (terrace) and 50m³ (semi/detached) volume limits for loft conversions remained unchanged. However, the 2025 amendments clarified the cumulative volume rule: any previous loft extension under PD or planning counts against the same volume allowance. This was always the legal position but was inconsistently enforced by some boroughs; the amendment removes any ambiguity.

New: front roof extensions (dormers on the front elevation) remain barred under PD. Side roof extensions on terraces also barred. Rear and roof slopes facing rear are permitted within volume limits.

Conservation areas: roof extensions usually require full planning rather than PD, formalised by the amendment. Mansards remain conservation-area-friendly in many London boroughs that have established mansard-friendly policies (Camden, Westminster) but still need full planning.

If you're planning an extension or loft conversion in 2026 in any inner London borough, allow extra time for planning. Where 2024 timelines might have been 6–8 weeks PD or 10–12 weeks planning, the 2026 reality is more like 8–10 weeks PD with consultation, 14–18 weeks planning in conservation areas.

Pre-application consultation with the planning officer is more valuable than ever — borough policies are interpreting the new amendments differently across London, and a 30-minute pre-app conversation can save 6 months of delay on a misjudged submission. We include pre-app discussion as standard on every project.

Heritage-friendly design becomes more important. Where prior approval was a relatively automatic path in 2024, 2026 requires more thoughtful design that pre-empts likely objections. Slim-frame glazing, matching brick, sympathetic detailing — these no longer cost a premium for marginal gain; they often determine whether your application succeeds.