Lawful development certificates for garden annexes and mobile homes

A lawful development certificate is a formal answer from your local planning authority to a narrow question: would what you propose to do be lawful? It is not a permission, and asking for one is not asking the council to allow anything. You are asking it to confirm, in writing, that the thing you have described does not need permission in the first place.

That distinction sounds academic until you are the one relying on it. A permission is a decision to grant something. A certificate is a determination that nothing needed granting. The two arrive on different forms, are assessed against different questions, and mean different things to a solicitor five years later.

Why homeowners apply for one

Nobody is obliged to. You can site a unit in your garden without ever writing to the council, and many people do. The reasons for getting it in writing are practical rather than legal.

• Certainty before spending. A garden annexe is a substantial purchase. Finding out afterwards that the authority takes a different view of it is an expensive way to learn.
• Selling the house. A buyer’s solicitor will ask what the building in the garden is and what authorises it. “Nothing, because it did not need anything” is a much better answer with a certificate behind it than without one.
• Enforcement. A council that takes an interest later starts from a very different position if the position has already been determined in your favour.
• Lenders and insurers. Both tend to ask, and both prefer documents to explanations.

What the council is actually deciding

This is the part most often misunderstood. When an authority considers a certificate application it is not weighing whether your annexe is a good idea. It does not consider whether the design is attractive, whether the neighbours object, or whether the area would be better without it. Those are the questions asked on a planning application, and they are not asked here.

The officer asks whether the facts you have described amount to something lawful. It is a legal question determined on evidence, and the burden of proving the facts sits with you, the applicant. That single point explains almost everything about how these applications should be prepared: an assertion is worth nothing, and a document is worth a great deal.

A certificate application is won or lost on what you can show, not on how persuasively you can describe it.

Proposed use, and use that already exists

There are two broad kinds of certificate. One deals with something you propose to do. The other deals with something already done, where the argument is usually that time has made it immune from enforcement.

AnnexeCert works on the first kind: proposals, before anything is sited. The second kind is a materially different exercise — the evidence is historical rather than technical, it usually turns on establishing dates, and where a unit is already in place and the council has taken an interest, the sensible first step is separate advice rather than an application.

Why a garden annexe is not a simple case

The reason these applications need care is that several separate questions have to be answered correctly at the same time, and getting six of them right does not help if the seventh is wrong.

1. Is the proposed position genuinely part of the residential curtilage of the house?
2. Does the unit meet the statutory description of a caravan, as built and as assembled?
3. Will the occupation genuinely be ancillary to the main house, rather than a second home?
4. Do the works involved in siting it amount to development in their own right?

Each is a question of fact, and each is evidenced differently. The curtilage question is answered with plans, photographs and history. The caravan question is answered with the manufacturer’s drawings, dimensions and mobility evidence. The occupation question is answered by the household describing honestly how it will live. The works question is answered by being specific about what will actually be built on the ground.

What a well-prepared application looks like

An officer reading your application should not have to hunt for anything. In practice that means scaled plans that show the site edged red with a north point and a scale bar, dimensioned drawings of the unit, technical evidence addressing each element of the caravan definition, a clear written statement of the household arrangement, and a schedule listing every document so nothing is assumed to have been read.

Applications are frequently returned before they are even considered, for reasons that have nothing to do with the merits — a missing scale, an unnumbered drawing, a plan that does not show the whole property. Those failures are avoidable, and avoiding them is most of what a managed service is for.

How long it takes, and what it costs

Authorities work to a statutory target of eight weeks from validation, though this varies and some take longer. Before that, preparation depends almost entirely on how quickly the property documents and the manufacturer’s technical evidence arrive. The council charges its own statutory fee, which is separate from any professional fee, and is paid to the authority.

If the answer is no

A refusal is not a fine and it is not an enforcement notice. It is the authority saying that on the facts presented, it is not satisfied the proposal would be lawful. Sometimes the response is to change the facts — move the unit, change the model, adjust the arrangement — and apply again. Sometimes the honest conclusion is that the proposal needs planning permission, which is a different application asking a different question.

The best time to discover which of those applies is before the application is made. See how a case is assessed and built.