What are the permitted development limits for a Worthing loft conversion?
Permitted development allows up to 40 cubic metres of additional roof volume on terraced houses and 50 cubic metres on other house types, alongside limits on roof height, side windows, eaves and roof overhangs.
The Planning Portal sets the national permitted development limits: a maximum additional roof volume of 40 cubic metres for terraced houses and 50 cubic metres for all other house types, with additional conditions covering maximum roof height (no part of the extension higher than the highest point of the existing roof), materials that visually match the existing house, no verandas, balconies or raised platforms, and side-facing windows required to be obscure-glazed and non-opening below 1.7m. Most single dormer and Velux conversions on standard Worthing terraces and semis fit comfortably within these limits.
What takes a loft conversion outside permitted development in Worthing?
Conservation areas, Article 4 Directions, a prior planning condition on the property, or a design (such as most mansards) that exceeds the volume or height limits all mean a full planning application is needed.
Parts of Worthing sit inside conservation areas — including areas of Tarring and Central Worthing — where controls are tighter, particularly for anything visible from the street or seafront. An Article 4 Direction can remove specific permitted development rights in a defined area regardless of the general national rules, and some properties carry a planning condition from a previous application that removes permitted development rights entirely. A mansard conversion, because it typically alters the roof pitch and shape beyond the standard limits, usually needs a full application regardless of location — see our mansard loft conversion guide.
Where a property sits near the northern edge of Worthing, it's also worth checking whether it falls inside the South Downs National Park boundary — the South Downs National Park Authority, not Adur & Worthing Councils, is the planning authority for sites within the Park.
How do I get a formal decision before starting work?
A Lawful Development Certificate from Adur & Worthing Councils gives a formal, legally reliable decision on whether a proposed loft conversion qualifies as permitted development.
Where it's unclear whether a project qualifies as permitted development, applying for a Lawful Development Certificate gives a formal decision from Adur & Worthing Councils rather than relying on an assumption — useful evidence to have on file, including at the point of a future sale. It is not a substitute for Building Regulations approval, which is assessed separately and covers the structural and safety side of the build (see our Building Regulations guide). The certificate confirms the legal planning status of the finished work, not its structural safety, so both processes typically run in parallel rather than one after the other on a real project timeline.