Homeowners often ask for “planning permission” when what they actually need is proof that they do not need it. Choosing the wrong route wastes money and, worse, time. This guide sets out the difference, how to tell which applies to your project, and why we recommend certifying permitted development even though the law does not require it.
What planning permission is
Planning permission is the council’s decision, under the Town and Country Planning Act 1990, that a proposal is acceptable against national and local policy. For a house extension or loft it is usually a householder application: drawings, forms, a fee of £528 (England, from 1 April 2025; verify before applying) and a statutory 8 weeks for a decision from validation. The council consults neighbours, weighs design, daylight and character, and grants with conditions, or refuses.
You need planning permission whenever the work is not covered by permitted development. That includes:
- any extension or roof alteration to a flat or maisonette, which have no householder permitted development rights;
- work that exceeds a permitted development limit, such as a rear extension deeper than 3 m on a terrace, a side extension wider than half the house, or a dormer over the volume allowance;
- roof extensions and side extensions in conservation areas, and most work where an Article 4 direction has removed the rights;
- listed buildings, which need listed building consent as well;
- changes of use outside the prior approval routes, and conversions of a house into flats.
What a Lawful Development Certificate is
A Lawful Development Certificate under section 192 of the same Act is the council’s formal confirmation that a proposed development would be lawful without planning permission, because it falls within permitted development. You submit the same quality of drawings, a written assessment against the relevant class of the permitted development order, and a fee of £264, half the planning fee. The council has 8 weeks to decide.
Crucially, the council is not judging whether it likes the scheme. It is checking facts and measurements against the order. Neighbours are not consulted, and design taste plays no part. That makes the outcome predictable when the drawings are right.
How to tell which one you need
Work through these in order:
- Is the property a house, not a flat? If it is a flat or maisonette, stop: you need planning permission.
- Is it in a conservation area or covered by an Article 4 direction? Check the council’s constraints map. Conservation areas remove permitted development for roof extensions and side extensions and close the larger home extension route; Article 4 directions remove whatever the direction says. Our area pages list the directions we know of for each council.
- Is the house listed? Then almost everything needs listed building consent, and usually planning permission too.
- Does the proposal sit within every permitted development limit? Depth, height, eaves, width, volume, materials, position relative to the front wall and the boundaries. All of them, measured against the original house, including previous extensions.
If you pass all four, a Lawful Development Certificate is the right route. If you fail any, plan for a householder application, and design to the council’s guidance from the start. Our permitted development guide sets out the limits in detail.
Why we recommend the certificate even when the work is clearly lawful
Permitted development is lawful without a certificate. We still recommend one on almost every project, for three reasons.
- Sale and remortgage. Buyers’ solicitors and lenders ask for evidence that extensions were lawful. Without a certificate you are relying on your own reading of the rules years later, against a council that may read them differently.
- Enforcement. A neighbour’s complaint triggers an investigation. With a certificate it ends in a day; without one you argue the measurements after the fact.
- The rules move. Permitted development limits and Article 4 directions change. A certificate fixes the position at the date of the decision.
Against those, the cost is £264 and a few weeks that usually run in parallel with the Building Regulations package, so the certificate rarely delays the build.
Costs and timelines side by side
| Householder planning application | Lawful Development Certificate | |
|---|---|---|
| Council fee (England, 2025) | £528 | £264 |
| Statutory decision period | 8 weeks | 8 weeks |
| Neighbour consultation | Yes | No |
| Assessed against | Policy and design guidance | Permitted development limits only |
| Expires | 3 years if not started | Does not expire |
Our own fee for the drawings and the application depends on the project type and size, and is fixed once quoted. Answer six questions in the instant estimate and we email you an indicative figure.
How we decide on your project
We check the constraints map for the address, measure the original house and any previous extensions from the survey, and test the proposal against each limit in writing. Where a scheme is close to a limit we say so and offer a choice: pull it inside the line for a certificate, or accept a planning application and design for approval. Either way you know the route, the fee and the timeline before we draw a line. See permitted development and LDC applications and householder planning applications for what each package includes.
