Lofts that fall under permitted development don't need planning permission, but most clients ask anyway, so here's the rule.
The short version
If your loft conversion stays within the permitted development (PD) envelope, you don't need to apply for planning permission. You still need Building Control sign-off, but the planning step disappears. Most London loft conversions we do fall on this side of the line.
If it doesn't fit the envelope, you apply for full planning permission, that's a separate council planning fee (the current figure is published on the Planning Portal, and it's re-set each April) plus our planning application work, which we price project by project on top of the drawing pack.
The permitted development envelope
For a loft conversion to be permitted development, all of these need to be true:
- Additional roof volume no more than 40m³ for a terraced house or 50m³ for a detached or semi-detached
- No extension beyond the plane of the existing roof slope on the front elevation (the side facing the road)
- No part of the extension higher than the highest part of the existing roof
- Materials similar in appearance to the existing house
- No verandas, balconies or raised platforms
- Side-facing windows must be obscure-glazed and either non-opening or more than 1.7m above floor level
- Roof extensions (other than hip-to-gable) set back at least 20cm from the eaves
Hit all of those, you're permitted development. Miss one, you're applying for planning.
One nuance that catches people out
The 40m³ / 50m³ figure is cumulative, if a previous owner already added a dormer or did a hip-to-gable, that volume counts against your allowance. We measure existing roof volume on the site visit; you'd be surprised how often a 40m³ proposal turns out to be 47m³ once we factor in what's already there.
The exceptions that void PD entirely
Permitted development rights don't apply at all if your house is:
- In a conservation area, even small dormers usually need planning
- A listed building, separate listed building consent is also required
- In an Area of Outstanding Natural Beauty (AONB), National Park, or the Broads
- A flat or maisonette, PD rights for loft conversions only apply to houses
- Subject to an Article 4 direction that has specifically removed loft-conversion PD rights (some London boroughs have these, Hackney, Camden and Islington all have parts under Article 4)
If any of those apply to your property, you're applying for planning permission regardless of how modest the design is.
"Lawful Development Certificate", worth getting?
When the work is permitted development, you don't have to apply for anything planning-related. But you can apply for a Lawful Development Certificate (LDC), a piece of paper from the council confirming the work didn't need planning permission. There's a council fee for it (lower than a full application; the current figure is on the Planning Portal).
Worth it if you're planning to sell within 5 years. Solicitors and surveyors increasingly ask for LDCs at conveyancing; without one, the buyer's lender can get twitchy. Most of our clients get the LDC done. We submit it with the same drawing pack we produce for Building Control, so there's no extra design work, just the application handling on top.
How we tell you which side of the line you're on
Before you book, we look at:
- Property type, house or flat, terraced/semi/detached
- Conservation area and Article 4 check, five minutes on the council's online map
- Proposed roof volume, rough sketch vs. the 40m³ / 50m³ ceiling
- Existing modifications, anything previous owners already did that eats into PD allowance
That happens before you pay anything. If you need a full planning application, you'll know about it before you book, with a written price for the planning work on top of the £1,650 drawing pack.
The honest version: if your loft is PD, we'll tell you, do the drawings, submit to Building Control, and you'll never deal with a planning officer. If it isn't, we'll tell you that too, and quote the planning application separately so you can decide before committing.
TL;DR
- Most lofts in London = permitted development, no planning permission needed
- Conservation area, listed building, flat, or Article 4 zone = planning permission required
- 40m³ / 50m³ is cumulative across all roof extensions, not just yours
- Get a Lawful Development Certificate if you're planning to sell within five years
- We tell you which side of the line you're on before you book