Are polytunnels development? The planning position

Whether a polytunnel needs planning permission turns on permanence, not on which class of the General Permitted Development Order it might fit. A single small tunnel moved around a market garden each season is often not development at all. A commercial soft fruit system of long, fixed hoop runs with irrigation, headland tracks and a plastic cover removed only in winter will normally be, and polytunnel planning permission is then required because the structures exceed the agricultural permitted development limits.

The difficulty is that the dividing line sits in case law rather than in a threshold table, and growers are often several seasons into an expanding operation before anyone asks the question.

Building or structure, and why it matters

Section 55 of the Town and Country Planning Act 1990 defines development as building, engineering, mining or other operations, or a material change of use. Section 336 defines a building as including any structure or erection, which is wide enough to catch a tunnel.

The courts assess whether something is a building operation using three factors: size, degree of permanence, and degree of physical attachment to the ground. None is decisive on its own, and the answer is reached on the facts.

In a 2006 High Court challenge about soft fruit polytunnels, the court was content that a large commercial tunnel system amounted to operational development, and the seasonal removal of the plastic covering did not alter that, because the hoops, legs and associated works stayed in place. Treat that as indicative of how the courts have approached the question rather than as a rule that settles every case.

Horticulture counts as agriculture for planning purposes, so the use of the land is rarely the issue. The structures are.

Permanence, size and attachment in practice

Four facts tend to decide the answer on a working holding.

Whether the legs are driven into the ground, set in concrete, or simply weighted. Driven or concreted legs point strongly towards a building operation.

How long the structure stands in one place. Tunnels erected for a six-week propagation window and taken down are at the opposite end of the scale from tunnels that have occupied the same field for four years.

The scale of the system. A single 30 metre tunnel is a different proposition from 40 tunnels in parallel runs covering five hectares with service roads between them.

The supporting works. Levelled pads, compacted alleys, buried irrigation mains, pump houses, water storage lagoons and hardstanding for picking are engineering operations in their own right, and they anchor the system in both senses.

The honest position is that a grower expanding year on year crosses the line at some point without a single decisive moment, which is why the question is usually raised by a neighbour's complaint rather than by the grower.

The agricultural permitted development route

Part 6 Class A of the General Permitted Development Order permits the erection of buildings reasonably necessary for agriculture on agricultural units of five hectares or more, subject to limits. Two of those limits rule out most commercial tunnels.

The ground area covered by the building must not exceed 465 m², counted together with any other building erected within 90 metres in the preceding two years. A commercial tunnel run passes that figure quickly, and the aggregation rule prevents incremental expansion from staying within it.

The building must not exceed 12 metres in height, reduced to three metres within three kilometres of the perimeter of an aerodrome, and must not be within 25 metres of the metalled part of a trunk or classified road.

Class A also requires prior notification: before starting a significant building you apply to the authority for a determination as to whether its prior approval of siting, design and external appearance is required, and the authority has 28 days.

Units between 0.4 and five hectares fall under Class B, which does not permit new buildings at all. So a smallholding has no permitted development route for a tunnel, whatever its size.

Tunnels rotated between fields

Rotation is a real agricultural practice and it is also the most common argument advanced against the need for permission.

It can work. Tunnels taken down at the end of a cropping cycle and re-erected elsewhere, with no concreted foundations and no permanent service infrastructure, sit much closer to equipment than to buildings. What undermines the argument is the surrounding evidence: an irrigation main serving every bay, a compacted track built to each run, and aerial imagery showing tunnels in the same field across several years.

If rotation is the basis of your position, document it. Keep a field plan for each season, dated photographs, and records of the dismantling and re-erection. That record is what a planning officer or an inspector will ask for, and reconstructing it after an enforcement notice is much harder than keeping it as you go.

Landscape effect in a National Landscape

In a National Landscape or National Park, Part 6 rights are restricted and the visual issue dominates any application.

Polytunnel plastic reflects light, and a run of tunnels reads as a pale sheet on a hillside from several kilometres away. Where an application is needed, a Landscape and Visual Impact Assessment prepared to the recognised methodology, with viewpoints agreed with the officer, is the document that carries it. Councils expect a suitably qualified author for landscape work and professional review is strongly advised.

The design measures that make a difference are specific rather than cosmetic. Keep runs below ridgelines and off open slopes. Break long runs into blocks with gaps that follow existing field patterns. Align runs with the contour and with existing hedge lines rather than cutting across them. Plant and manage hedgerow screening before the tunnels go up, not as a condition afterwards. Remove covers outside the growing season where the cropping allows, and say so in the application, because it is a real reduction in effect for part of the year.

Expect conditions on the area covered, the colour and finish of the cover, a landscape scheme with a management period, and sometimes a requirement to remove covers for a stated period each year.

Drainage and surface water from tunnel runs

A tunnel is an impermeable surface during the growing season, and the water it sheds arrives in the alleys between runs as a concentrated flow.

Three consequences follow. Erosion and sediment loss from the alleys, which ends up in a ditch and then in a watercourse. Increased peak run-off from the holding, which the lead local flood authority will ask about on any sizeable application. And a pollution pathway for fertigation residues and crop protection products.

The answer is a drainage design that keeps water on the holding: grassed alleys or swales between runs, cross-slope interception, buffer strips along watercourses, and attenuation where the receiving ditch is sensitive. A Drainage Strategy covering those elements is worth preparing even where the application does not strictly demand one, because the alternative is a condition written by someone who has not seen the field. The thinking is the same as the drainage condition attached to hard surfaces under Class F at a dwelling, scaled up.

Settling the position with a certificate

Where the answer matters to a lender, a buyer or a packer contract, informal reassurance is not enough.

A certificate of lawfulness of proposed use or development under section 192 of the Town and Country Planning Act 1990 gives a formal determination that specified works do not require permission. For tunnels already in place for a long period, a certificate of existing lawful development under section 191 may be available on the evidence.

Either way the evidence standard is documentary: dated photographs, field plans, invoices for materials, cropping records and contractor records. A Planning Statement that assembles the chronology and applies the size, permanence and attachment tests to it is the document to put in front of the authority.

Some authorities in the main soft fruit areas have adopted supplementary planning documents on polytunnels, covering siting, scale and landscape mitigation. Check whether yours has, because where one exists it tells you exactly what the officer will assess.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A Lawful Development Certificate is the only formal way to confirm that works are lawful.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter the holding postcode on PlanScope to see which reports a horticultural application is likely to need.