Shipping containers and portable buildings on a site

A shipping container sitting on a commercial yard for three years is a building in planning terms, and placing it there was development that needed permission. A container delivered on Monday and collected on Friday is not. Nothing in between is settled by whether it is bolted down, because physical attachment is only one of three tests and it is the least important of them.

That is the answer most operators do not want, so it is worth understanding how the tests work and which permitted development rights can help.

When a container becomes a building in planning terms

Section 336 of the Town and Country Planning Act 1990 defines a building as including any structure or erection and any part of a building, excluding plant or machinery comprised in a building. The definition is deliberately wide, and the courts have filled it in.

The working test comes from the Cardiff Rating Authority case in 1949 and asks three questions: what is the size of the thing, what degree of permanence does it have, and what is its degree of physical attachment to the ground. All three are weighed together.

Skerritts of Nottingham v Secretary of State in 2000 settled the point that attachment is not decisive. A large marquee erected for eight months of each year and then taken down was held to be a building, because its size and the degree of permanence outweighed the absence of fixing. A twenty foot container weighing more than two tonnes, standing on a yard season after season, is a long way beyond a marquee on either measure.

So the practical rule for a commercial operator is that a container intended to stay for a season or longer, used as storage, an office, a workshop or a cafe, is development. Placing it is the operation. No alteration to the container itself is required for that to be true.

Size, permanence and attachment

Applying the three tests to real situations gives a workable shape.

The grey area is a yard where containers are stock in the ordinary sense, arriving and leaving. There the issue shifts from operational development to change of use, because a yard filled with containers for hire is a storage and distribution operation, and whether that is a material change of use depends on the lawful use of the land.

Both questions can arise on the same site. A container hire yard may involve a change of use and the placing of a permanent office building, and the application should address both.

Temporary buildings during construction works

The most useful right for a commercial operator is in Part 4 of Schedule 2 to the General Permitted Development Order. Class A permits the provision on land of buildings, moveable structures, works, plant or machinery required temporarily in connection with and for the duration of operations being carried out on that land, or on land adjoining it.

That covers site offices, welfare cabins, secure stores and container workshops for the duration of a construction project, without an application. The conditions are strict and they are where the right is lost:

• The building or structure must be required temporarily in connection with the operations, not merely convenient
• It must be removed when the operations are completed
• The land must be reinstated to its former condition, or to a condition the authority agrees
• The right attaches to the operations, so it ends when they do, whatever the commercial need afterwards

Operators routinely keep the cabin after practical completion because it has become the site office. At that point the right has expired and the cabin needs permission. Where the works themselves are permitted development or do not need permission, read the Class A wording carefully, because the right is tied to operations being carried out.

What Part 7 does and does not allow

Part 7 of Schedule 2 deals with non-domestic extensions and alterations, and includes rights for industrial buildings and warehouses, for hard surfaces within their curtilage, and for plant and machinery on industrial land. Each class has its own limits on height, floor area, proximity to boundaries and relationship to the original building, and several are disapplied on article 2(3) land, which covers conservation areas, National Landscapes, National Parks, the Broads and World Heritage Sites.

The thing Part 7 does not do is authorise a free-standing container. The industrial and warehouse rights are about extending or altering a building, so a container placed beside the warehouse is not an extension of it. A container physically joined to the warehouse and forming part of it might be, and that is a question of fact worth testing with the authority before relying on it.

The plant and machinery right is also narrower than it sounds. A container is not plant or machinery. A compressor housing or a chiller unit may be.

Read the current text of Part 7 in the Order rather than a summary, because the classes and their conditions have been amended repeatedly, and the version your consultant remembers may be out of date.

Surfacing, drainage and the engineering question

Containers need something to stand on, and the base is often the part that needs permission when the container itself might have escaped it.

Laying a substantial area of concrete or hardcore can be an engineering operation amounting to development. Within the curtilage of an industrial building or warehouse there is a limited right for hard surfaces, subject to conditions including the use of permeable surfacing or the provision for run-off to a permeable area. The principle is the same one that applies to domestic front gardens, which is explained in the note on permeable surfaces and front garden paving.

Surface water is where the authority's attention goes. A yard that was gravel and grass and is now sealed concrete discharges more water, faster, and the lead local flood authority will say so. Where the area is significant, expect to be asked for a drainage strategy showing attenuation and a discharge rate at or below the pre-development rate.

Flood risk and containers

An empty shipping container floats. In a flood it becomes a large, buoyant, hard object travelling at the speed of the water, and it can block a culvert, breach a wall or strike a building downstream.

Authorities and the Environment Agency take this seriously on sites in Flood Zone 2 and 3. Expect to be asked how containers will be secured or anchored, whether they will be kept out of the floodplain, and what the flood response procedure is. A scheme that locates containers on the lowest part of the site because it is the least visible will attract an objection.

Where the site is at risk, say how you will manage it rather than waiting to be asked. Anchoring details, a minimum level for the base, a flood warning signup and a procedure for moving units are all answerable.

Regularising containers already on site

Three routes exist and the right one depends on how long the containers have been there.

1. A retrospective planning application under section 73A of the 1990 Act, which allows permission to be granted for development already carried out. This is the normal route and it is what an enforcement officer will usually invite.
2. A certificate of lawfulness of existing use or development under section 191, where the containers have been in place long enough to be immune from enforcement. The Levelling-up and Regeneration Act 2023 replaces the former four year immunity period for operational development with a single ten year period in England, so check the current commencement position and the transitional arrangements on gov.uk before relying on either figure.
3. Removal, where the containers are in a position that cannot be defended, such as within the visibility splay of an access or on a prominent frontage.

Act before an enforcement notice is served. Once a notice exists the options narrow, the timetable is fixed by the notice, and an appeal is slower and more expensive than an application would have been. A short planning statement addressing siting, appearance, drainage and the operational need does most of the work on a retrospective application.

Conditions to expect

Permissions for containers and portable buildings are usually conditioned tightly, and the conditions deserve a careful read before you agree to them.

Expect a limit on the number and the positions, shown on an approved plan. Expect a colour or finish condition, often requiring a muted colour and sometimes cladding or a screen. Expect a landscaping or boundary treatment condition where the site is visible from a road or from housing. Expect a condition restricting use to purposes ancillary to the main operation, which prevents a container becoming a separate unit let to a third party.

Temporary permissions are common for cabins and containers, typically for three or five years with a removal requirement. They are not a bad outcome. A temporary permission gives the authority a way to agree to something it is uncertain about, and renewal is straightforward where the unit has caused no problems. The structure-versus-separate-unit question that drives the ancillary use condition is the same one discussed in the note on garden offices and the separate planning unit problem.

Enter your postcode on PlanScope to see which documents your site is likely to need.

This is general guidance, not legal advice. A certificate under section 191 or 192 is the only formal way to confirm that works or a use are lawful, so check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.