Planning guide · England & Wales
Most loft conversions can be done under permitted development — but the volume allowance, dormer placement and rooflight rules trip people up. Here is how it works in England and Wales, and how we get yours drawn and approved at a fixed price.
Frequently, no. Many loft conversions — including rear dormers and hip-to-gable conversions — are permitted development provided they stay within a set additional roof volume and follow the design rules below.
You will need full planning permission if you exceed the volume allowance, add a dormer to the roof slope facing a highway at the front, raise any part above the existing ridge, live in a flat (permitted development removed), or your home is on designated land, where dormers and cladding usually lose permitted development — though a rooflight-only conversion may still qualify.
Loft conversions are judged on added roof volume and where any dormers sit. Here is how each nation treats them.
We are an online architectural design service — the practical alternative to a traditional high-street architect. Our qualified design team draws your plans, works out whether you are permitted development or need a full application, and deals with the council on your behalf.
Often not. Many loft conversions are permitted development if they stay within the added-volume allowance (about 40 cubic metres for a terraced house, 50 for a semi or detached), keep below the existing ridge, and avoid a dormer on the front roof slope facing a highway. Larger conversions, flats, and homes on designated land usually need full planning.
In England you can add up to 40 cubic metres of roof space on a terraced house, or 50 cubic metres on a semi-detached or detached house. Wales uses broadly similar limits under its own order. The allowance includes any previous roof enlargements.
Usually yes for rear and side dormers within the volume limits, as long as nothing sits above the existing ridge. A dormer on the principal roof slope facing a highway is not permitted development and needs full planning. On designated land, dormers generally lose permitted development.
Usually not. A conversion that only adds rooflights sitting close to the roof plane (no more than 150mm proud) is typically permitted development, and often remains so even on designated land where dormers would not. It still needs building regulations approval.
Always. A loft conversion changes the structure of your roof and creates a habitable room, so it needs building regulations approval covering the new floor, fire escape, staircase, insulation and ventilation — whether or not planning permission was required.
Often, yes. If the work affects a shared wall with a neighbour — common in terraced and semi-detached homes — you may need a Party Wall agreement. It is separate from planning and building regs, and we will flag it as part of your project.
No call required, no card required — just a tight, fixed-price range tailored to your project, with the planning route confirmed for your address.
This guide is general information, not planning advice, and permitted development rules change and depend on your specific property and local authority. We confirm the current position for your address as part of every project.