Permitted development rules for skylights
Under Class A and Class B of Schedule 2, Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015, rooflights (skylights) on a dwellinghouse are permitted development when they meet specific criteria. The key conditions are: the rooflight must not project more than 150mm above the plane of the roof slope; the rooflight must not be higher than the highest part of the roof (the existing ridge); the rooflight must not be installed on a roof slope forming part of the principal elevation (the front of the house) that faces a highway; and the overall roof volume must not exceed the permitted development limits. In practice, the vast majority of Velux-style flat-glass or slightly projecting roof windows installed in a rear or side roof slope of a London terrace automatically meet all these conditions — no planning application is needed, and no Lawful Development Certificate is required (though one can be obtained for £220 as a precaution). The 150mm projection rule catches 'conservation spec' flush-fit rooflights that project only 5–10mm, as well as standard Velux Centre-Pivot models that project approximately 140mm — both are PD-compliant.
Conservation areas and rooflights
In a conservation area, the PD rights for roof alterations are modified by the conservation area provisions within the GPDO. The most significant restriction: any enlargement or alteration of a roof slope on the 'principal elevation' (broadly, any elevation facing a road or public space) that results in material alteration to the appearance requires planning permission. Installing a rooflight on a front roof slope in a conservation area, where the rooflight will be visible from a highway or public space, always requires a planning application. Conservation area rooflights on front slopes are frequently approved when specified as 'conservation-specification' flush-fit rooflights (Velux Conservation range, Conservation Roof Window or equivalent) — these sit within 6mm of the surrounding tile surface and read as minimal interventions from street level. Rear and side roof slope rooflights in conservation areas are still PD in most London boroughs, but some conservation area design guides require that rooflights should be 'discrete in scale and character' and 'match the profile of surrounding slates or tiles as closely as possible'. Several inner London LPAs (Kensington and Chelsea, Westminster) have adopted Article 4 directions that remove PD rights for rooflights on all roof slopes — always check Article 4 status before assuming PD.
Listed buildings and skylights
Listed buildings require Listed Building Consent (LBC) for any works that affect their character, whether internal or external. Installing a skylight in a listed property — even on a rear roof slope with no visibility from any public space, and using conservation-specification flush-fit glazing — requires LBC. This is a strict liability position: there is no de minimis exemption and no permitted development analogue for listed buildings. The application itself is usually straightforward for a single well-specified rooflight: a standard LBC application with drawings, description, and photographs, submitted to the LPA. Most conservation officers support rear-slope rooflights in conservation-specification when the proposed rooflight is positioned between rafter bays, uses flush-fit glazing, and does not require structural alteration to the roof assembly. Retrospective LBC is possible but carries criminal liability risk — unauthorised works to a listed building are an offence under Section 9 of the Planning (Listed Buildings and Conservation Areas) Act 1990, with penalties of unlimited fine or imprisonment. Builderr confirms listing status at the outset of all roof projects and obtains all necessary consents before work begins.
Flat roof skylights and glazed rooflights
Roof lanterns and flat rooflights (pyramid, rectangular or flat glass) on flat roof extensions are a ubiquitous feature of London kitchen extensions and have become one of the defining design elements of the 2010s and 2020s London residential extension. Where the flat rooflight is part of the original extension design, it is covered by the extension's planning permission — no separate rooflight consent is needed. Adding a new rooflight to an existing flat roof that was not part of the original extension is Class A PD: permitted provided the rooflight does not project more than 150mm above the flat roof surface and the other PD conditions are met. A flat glass rooflight flush with or slightly above the roof surface is clearly PD. A full-height pyramid roof lantern (which by definition projects substantially above the flat roof level) may not meet the 150mm projection limit and should be checked against the specific dimensions. On a conservation area flat roof extension, a flush-fit flat rooflight is PD (not on the principal elevation, projection minimal); a prominent roof lantern may require a planning application if visible from a public space.
