Do You Need Planning Permission for a Velux Window in Aylesbury?

The Permitted Development Rules

Under the Town and Country Planning (General Permitted Development) Order 2015, roof windows are permitted development (no planning permission needed) provided they meet all of the following conditions: the window does not protrude more than 150mm above the existing roof plane when measured from the plane of the roof slope; the highest point of the window is not higher than the highest part of the existing roof; and the window is not installed on a wall or roof slope that fronts a highway.

In practice, all standard Velux windows with their standard installation flashings are designed to sit within the 150mm limit — this isn’t usually the restricting factor. The key conditions to check are whether the slope in question faces a highway, and whether you’re in a conservation area or a listed building.

When You Do Need Planning Permission

Conservation areas: Aylesbury town centre has a conservation area covering the historic core around Market Square, Temple Street, and the Kingsbury quarter. Properties within this zone need planning permission for any roof alteration on a slope that is “visible from a highway” — which in practice means any elevation that a member of the public can see from a public road or footpath. In a dense town centre street, this can include rear slopes if visible from an adjacent street. Always check with Buckinghamshire Council’s planning portal before proceeding in the conservation area.

Listed buildings: Any Aylesbury property that is listed (Grade I or II) requires listed building consent for any alteration to the external appearance, including roof windows. This is separate from planning permission and must be applied for even where the PD rules would otherwise permit the work. The consent process considers the impact on the listed character of the building.

Principal elevation facing a highway: If the slope where you want the window directly faces the road your property fronts onto, the PD right does not apply and you need to apply for planning permission. This affects relatively few residential properties — most homes have their primary windows on the rear or side slopes — but it catches some end-terrace and corner plots.

Conservation Flashings for Aylesbury Town Centre Properties

For properties within or adjacent to Aylesbury’s conservation area where planning permission is granted or not required, Velux offers a conservation flashing kit (the EDW system) that positions the window lower in the roof plane and sits significantly flatter than the standard flashing. This is often a condition of planning consent for conservation area properties and is the correct specification for period homes where maintaining the character of the roofline matters. It adds approximately £120–£200 to the installation cost.