Most single-storey rear extensions and loft conversions that stay within strict size limits fall under permitted development and need no planning application. Side extensions, two-storey extensions and any work to flats almost always require full planning permission. Conservation area status, listed status and Article 4 directions reduce or remove permitted development rights entirely.
It's the first question almost every homeowner asks, and the honest answer is: it depends on what you're building, what type of property you own, and where it sits. This guide explains how to work out which side of the line your project falls on before you spend money on drawings.
What is the difference between planning permission and building regulations?
Planning permission and building regulations are not the same thing. Planning permission is about whether you're allowed to change the property — its size, shape and appearance, and the effect that has on neighbours and the street. Building regulations are about whether what you build is structurally safe and properly constructed. Many projects need both, some need only one. Getting planning permission does not mean you can skip building control.
What does permitted development actually mean?
Permitted development rights let you carry out certain works without a full planning application. They exist so that modest, uncontroversial improvements don't clog up the planning system. The catch is that they come with detailed limits on size, height, position and materials — and exceeding any one of them takes you out of permitted development entirely.
Broadly, the kinds of project that often fall under permitted development include:
- Single-storey rear extensions within set depth and height limits
- Loft conversions that stay within volume limits and don't alter the roofline dramatically
- Modest outbuildings and garden rooms that cover only part of the garden
- Some porches, subject to size limits
Which projects always need a full planning application?
Some projects sit outside permitted development from the start:
| Project type | Usual route | Principal qualifier |
|---|---|---|
| Single-storey rear extension | Often permitted development | Depth, height and boundary limits apply |
| Side extension | Full planning application | Rarely permitted development |
| Two-storey extension | Full planning application | — |
| Loft conversion, no roofline change | Often permitted development | Volume limits apply |
| Rear dormer | Depends on volume and location | Restricted in conservation areas |
| Mansard conversion | Full planning application | Substantial roofline alteration |
| Outbuilding / garden room | Often permitted development | Garden coverage and height limits |
| Flat or maisonette | Full planning application | PD rights generally do not apply |
- Side extensions — these nearly always require full planning permission
- Two-storey extensions — typically require an application
- Flats and maisonettes — these generally don't benefit from the same permitted development rights that houses do
- Anything altering the front elevation facing a highway
- Mansard conversions and major roofline changes
What can remove your permitted development rights?
Two properties can be identical in size and still get different answers, because permitted development is restricted or removed altogether in certain circumstances:
- Conservation areas — rights are reduced, and works that would be permitted elsewhere often need consent
- Listed buildings — listed building consent is a separate requirement, and it applies to interior work too
- Article 4 directions — a council can withdraw permitted development rights for a specific area
- Previous extensions — earlier work may have already used up the allowance attached to the property
- New-build estates — planning conditions sometimes remove rights from the outset
Do I need a Lawful Development Certificate?
Even when your project genuinely is permitted development, that's a claim you may later have to evidence — typically when you sell. A Lawful Development Certificate is the formal way to have a council confirm the works were lawful. Buyers' solicitors ask about this more often than people expect, and it is considerably easier to obtain before the work is done than years afterwards.
What drawings do I need for a planning application?
Either route needs accurate drawings. A planning application requires existing and proposed floor plans, elevations, and a site plan drawn to scale and to the standards your local authority expects. A permitted development or lawful development certificate application needs drawings that demonstrate the scheme sits inside the limits.
Our planning drawings start at £1,100 and are delivered within two weeks, with a 98% first-time approval rate across more than 150 projects. If your project also involves removing a load-bearing wall or adding a beam, the Full Package at £1,650 covers planning, structural calculations and building regulations together.
Does the answer change between local authorities?
The national permitted development framework is consistent across England, but its application is not. Individual authorities operate Article 4 directions, conservation area designations and local validation requirements that change both what is permitted and what a valid application must contain.
We prepare drawings to the submission standards of the authority receiving the application, including Surrey authorities such as Elmbridge, Guildford, Woking, Waverley and Mole Valley, and South London boroughs including Lambeth, Wandsworth, Merton, Croydon and Richmond upon Thames.
Please note: this guide is general information for UK homeowners, not a formal planning determination. Rules vary by local authority and by property — conservation areas, listed buildings and Article 4 directions all change what applies. We confirm exactly what your project needs as part of your free quote.