The Caravan Act and garden annexes: what the law says

“The Caravan Act” is shorthand for two pieces of legislation: the Caravan Sites and Control of Development Act 1960, which defines what a caravan is, and the Caravan Sites Act 1968, which extends that definition to twin-unit structures and sets their maximum size. Between them, they decide whether a garden annexe or mobile home is legally a caravan — and that is the first of the questions that decide whether you need planning permission.

It is only the first. A unit can be a perfect caravan and still need permission if it is in the wrong place or used in the wrong way. This guide covers the definition; the others cover where it can go and how it must be used.

The legal definition of a caravan

Section 29(1) of the 1960 Act defines a caravan as any structure designed or adapted for human habitation which is capable of being moved from one place to another — whether by being towed, or by being transported on a motor vehicle or trailer (s.29). Tents and railway carriages are excluded.

A single-unit mobile home that can be lifted onto a lorry fits that description readily. Most garden annexes are bigger, and are built in two halves joined on site — which is where the 1968 Act comes in.

Twin-unit annexes: the three tests

Section 13 of the 1968 Act treats a twin-unit structure as a caravan, even though it is too big to travel on a road once assembled, if it meets all of these (s.13):

1. Construction. It is made of no more than two separately constructed sections, designed to be assembled on site by bolts, clamps or other devices.
2. Mobility. Once assembled, it is physically capable of being moved by road from one place to another — towed, or carried on a vehicle or trailer — as a whole.
3. Size. It does not exceed the maximum dimensions below.

Maximum dimensions in England

• Length: 20 metres (65.616 feet), excluding any drawbar.
• Width: 6.8 metres (22.309 feet).
• Internal height of the living accommodation, floor to ceiling at its highest point: 3.05 metres (10.006 feet).

These limits have applied in England since 1 October 2006, when they were set by statutory instrument (S.I. 2006/2374). Wales adopted the same figures from 30 November 2007.

Mobility is where cases fail

The mobility test is the one applications most often get wrong, because it is the one most often asserted rather than shown. A brochure line saying a unit is “fully mobile” or “meets the Caravan Act” is not evidence. What a council will look for is how the assembled unit would actually be moved: where it would be lifted or towed from, what it sits on, and whether the services can be disconnected.

The same point applies on site. A unit that is bolted to a permanent foundation, built into the ground, or has rooms added on so it can no longer be moved as a whole, risks being treated as a building — at which point the caravan route no longer applies.

Mobile homes in your garden

A mobile home, static caravan or lodge in a residential garden is assessed exactly the same way. If it meets the definition above, sits within the curtilage of your house and is lived in as part of your household — a parent, or an adult child — siting it does not normally need planning permission. If it is let to someone else, or used as a separate home, it does.

Separately, the 1960 Act normally requires a site licence for land used as a caravan site, but not where the caravan is within the curtilage of a house and used incidentally to the enjoyment of that house (Schedule 1, paragraph 1).

Common misconceptions

• “The Caravan Act means no planning permission is ever needed.” It means the unit can be a caravan. Location and use still have to be right.
• “Outbuilding size rules apply.” Permitted development limits for outbuildings — heights, the half-of-the-garden rule — are a different regime. A caravan is not relying on them.
• “It must not have a kitchen or bathroom.” Facilities do not decide the question; how the household lives does.

The way to confirm all of this before you buy is a lawful development certificate. Start with the overview of granny annexe planning if you have not already.

Sources

• Caravan Sites and Control of Development Act 1960, section 29
• Caravan Sites and Control of Development Act 1960, Schedule 1
• Caravan Sites Act 1968, section 13, as amended by S.I. 2006/2374

Checked against the legislation in October 2026. This guide explains general principles for England; it is not advice on any particular property.