What pushes a loft conversion from permitted development into needing planning permission across England — roof volume, dormers, designations — and what to check before you design.
Loft conversions sit on the boundary between permitted development and full planning permission more often than any other home project. The national rules turn on a roof volume allowance and a set of conditions about where dormers can go, what materials are used, and how windows face. This guide explains where that line falls across England.
These are the common features that keep a project on the simpler route.
These are the usual triggers that push a scheme beyond straightforward PD rights.
The tool is designed to answer the first question most homeowners have: is this worth pursuing, and what is most likely to block it?
CanUBuild checks your exact address against national datasets for the designations that most affect roof work.
The loft workflow focuses on dormer position and size, ridge height, roof volume, rooflights and window orientation.
You see nearby decided loft and dormer applications, grounding the national rules in your authority's actual decisions.
National permitted development sets a roof volume allowance that is smaller for terraced houses than for semi-detached and detached homes. Staying within it, and meeting the dormer and materials conditions, keeps a conversion permitted development.
A modest rear dormer, set back from the eaves and within the volume allowance, can be permitted development. A front dormer, or one that breaches the volume limit, usually needs planning permission.
Conservation area controls commonly restrict permitted development for roofs, so visible changes such as dormers are more likely to need permission and a more sympathetic design.
Confirm your roof volume allowance, whether your permitted development rights are intact, and whether any designation applies to your property — all available from an address-level check.
Search for the address, choose your project type, and get a planning feasibility answer based on permitted development rules, constraints, and local precedent data.