Polytunnels: development, agriculture or neither

The polytunnel planning permission question has no single answer, and anyone who tells you polytunnels are agriculture and therefore exempt has skipped a step. Using land for agriculture is not development, so the growing is never the issue. Erecting structures on that land can be a building operation, and whether a particular tunnel counts turns on its size, its degree of permanence and how firmly it is attached to the ground. Those three factors have decided every reported case on the point, and they are the ones a council will apply to yours.

Whether a polytunnel is a building operation

Section 55 of the Town and Country Planning Act 1990 defines development as the carrying out of building, engineering, mining or other operations, or the making of a material change in the use of land. Section 336 defines a building as including any structure or erection.

That definition is wide enough to catch a polytunnel on its face. The courts have refined it through a three-part test drawn from rating law and applied in planning: size, permanence and physical attachment. A structure large enough to dominate its surroundings, standing for a substantial part of the year, and fixed into the ground is a building. One that is small, seasonal and simply weighted down is less likely to be.

The leading planning application of that test to a soft fruit holding found that extensive polytunnel systems did amount to development requiring permission, both as operations and through the change they made to the character of the land. Since then most authorities have treated large-scale tunnel blocks as needing an application, and the argument has moved on to scale and conditions rather than to principle.

Section 55(2)(e) is the provision people reach for. It says the use of land for agriculture, and the use for that purpose of any building occupied with land so used, is not development. It excludes the use. It does not excuse the erection of the structure.

The degree of permanence and physical attachment

Work through the factors honestly before deciding whether to apply.

Size means both the individual tunnel and the block. Twenty tunnels in a field read differently from one behind a farmhouse, and cumulative extent is what officers look at.

Permanence means how long the structure stands, not how long it is intended to stand. Tunnels that are skinned in February and stripped in November, with the hoops left in place all year, are hard to present as temporary. Tunnels dismantled completely each season, hoops included, are a better case.

Attachment means what happens below ground. Hoops driven into the soil or set into concrete pads are attached. Hoops sitting in ground anchors that are lifted out with a tractor are less so. Anything with a permanent hard standing, a concrete pad or a fixed irrigation main has moved decisively towards being a building.

Mobile systems on rails or skids occupy the middle ground, and the position remains unsettled. Plan for an application rather than a dispute.

Where permitted development rights assist

Part 6 of Schedule 2 to the General Permitted Development Order 2015 gives agricultural permitted development rights, and they can cover a structure that qualifies as a building.

On a unit of five hectares or more, Class A permits works reasonably necessary for the purposes of agriculture, subject to conditions that include a limit on the ground area covered by any building, height restrictions, a restriction on siting near a metalled classified road, and a prior notification procedure for the siting, design and external appearance of certain buildings. Units between 0.4 and five hectares have narrower rights under Class B.

Three traps. The ground area limit applies across works carried out on the unit, so a phased expansion can run out of allowance. The rights do not apply on article 2(3) land in the same way, and National Parks and National Landscapes have their own restrictions. And prior notification is a real procedure with a real deadline, not a formality: build before the authority has responded and the right is not engaged.

Check the current text of Part 6 before relying on any of this, because the agricultural classes have been amended several times.

Landscape and visual objections in practice

This is what the objections are actually about. Polythene reflects, and a block of tunnels reads as a white or silver mass that has no precedent in an agricultural landscape.

The arguments that carry weight in mitigation are field-by-field phasing so that the whole holding is never under cover at once, retention and reinforcement of hedgerows on the skyline, avoiding the crest of a slope, orienting runs along rather than across the contour, and stripping the polythene outside the growing season where the crop allows.

Where the site is in or near a National Landscape or National Park, or is visible from a well-used footpath, expect the authority to want proper viewpoint analysis rather than assertion. The approach is the one set out in the notes on landscape and visual evidence for a countryside application, and on a large holding a formal Landscape and Visual Impact Assessment is proportionate.

Drainage and run-off from tunnel blocks

The hydrology is the technical issue that most applications underplay.

A tunnel is an impermeable roof. Rain that would have fallen evenly across a field is shed to the gutter lines between tunnels and concentrated there, which produces channel erosion, silt-laden run-off and, on a slope, a real increase in peak flow reaching the nearest ditch or watercourse.

Deal with it explicitly. Set out the catchment area of the tunnel block, where the water is directed, and what attenuation or infiltration is provided. Grass gutter strips, cross-drains, silt traps and attenuation ponds are all standard. Where the receiving watercourse is sensitive, or the land drains towards a designated site, the case needs to be made properly rather than asserted.

Access tracks servicing the tunnels raise their own questions about surfacing and run-off, covered in the notes on farm tracks and new accesses.

Conditions on removal and seasonal use

Where permission is granted, expect conditions. The common ones limit the area that may be covered at any one time, require polythene to be removed outside a defined period, restrict the height and the colour of the sheeting, require gutter management and silt control, and secure landscape planting with a replacement clause.

Some permissions are granted for a limited period, which gives the authority a review point. That is not automatically a bad outcome for a grower, since it allows a scheme to be tested against real landscape and drainage effects rather than predicted ones.

Offer workable conditions rather than resisting all of them. A condition you have drafted around your own cropping cycle is easier to live with than one an officer writes from a template.

Retrospective applications and enforcement

A good many tunnel blocks go up first and get discussed later, sometimes because the grower took the view that no permission was needed.

If that is your position, the safer route is a certificate of lawfulness rather than silence, because a certificate settles the question permanently. If the tunnels do amount to development and are not immune through the passage of time, a retrospective application under section 73A is the route, with the same evidence a prospective application would need plus accurate drawings of what is actually there.

Enforcement in this area is usually proportionate, and authorities are generally more interested in securing landscape mitigation and drainage control than in clearing a field. An unresolved enforcement file does, though, affect any sale or refinancing of the holding, and it is a poor thing to leave sitting.

Enter your postcode on PlanScope to see which reports a horticultural scheme is likely to need, or browse the 66 report types. This is general guidance, not legal advice. 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.