Putting up polytunnels on a horticultural holding

Whether you need planning permission for polytunnels turns on one question: are they development? Section 55 of the Town and Country Planning Act 1990 catches "building operations", and the courts have treated substantial, long-standing polytunnel blocks as buildings even where the covers come off each winter. Small, properly movable tunnels on a market garden are a different matter. If they are buildings, the next question is whether the agricultural permitted development rights in Part 6 of the GPDO 2015 cover them, and on most commercial holdings they do not, because the area involved is far beyond the Part 6 ceiling.

Whether a polytunnel is development at all

The statutory test has three limbs that planning inspectors apply to any structure: size, permanence, and the degree of physical attachment to the ground. A tunnel 90 m long on driven steel hoops set in the soil, in place for eight years with the polythene replaced every third season, scores on all three. A 6 m hoop house moved between beds each spring scores on none.

Horticulture counts as agriculture under section 336 of the 1990 Act, so the agricultural definitions apply to soft fruit, salad crops and nursery stock. That helps you with permitted development and with the policy case, and it does not exempt you from needing permission where the structures amount to building operations.

The honest position is that there is no square-metre threshold in the legislation that separates a building from a temporary crop cover. Inspectors decide it case by case, and the pattern of appeal decisions is indicative rather than binding. Where a holding has invested in a permanent hoop layout with service tracks and irrigation mains, treating it as development and applying is usually the cheaper route than defending an enforcement notice later. A Lawful Development Certificate under section 191 or 192 is the only formal way to confirm that works are lawful.

Permanence, anchoring and the Part 6 route

Part 6 Class A of the GPDO 2015 permits agricultural buildings on units of five hectares or more, subject to conditions that rule out most tunnel blocks:

• The ground area covered must not exceed 465 m², aggregated with any building erected within 90 m in the preceding two years.
• Height must not exceed 12 m, reduced to 3 m within 3 km of the perimeter of an aerodrome.
• Nothing within 25 m of the metalled part of a trunk or classified road.
• The building must be reasonably necessary for the purposes of agriculture within the unit.

Where Class A does apply, significant development still needs prior approval of siting, design and external appearance from the local planning authority, applied for on the Part 6 notification. Units between 0.4 and 5 hectares fall under Class B, which does not permit new buildings at all. On land in a National Park, the Broads, a National Landscape or a conservation area the restrictions tighten further.

The practical consequence for a commercial holding is simple arithmetic. One hectare of tunnels is 10,000 m², more than twenty times the Class A ceiling, so a full planning application is the route. Design the application around the anchoring detail, because inspectors and officers both read it as the marker of permanence: pile-driven hoops with concrete footings read as buildings, ground anchors with removable feet read as something less.

Landscape and visual effects of large blocks

Polythene reflects light. That is the whole landscape objection in one sentence, and it is why applications for extensive tunnel blocks fail in sensitive countryside more often than they fail on agricultural need.

The assessment needs to cover the reflective surface as seen from public vantage points, the cumulative effect where neighbouring holdings also have tunnels, the visual effect of the gutters and service tracks between blocks, and what the site looks like in the weeks when covers are off and bare hoops are exposed. A Landscape and Visual Impact Assessment prepared to GLVIA3 is proportionate for anything above a couple of hectares or anything within or adjoining a National Landscape.

Mitigation that officers accept tends to be specific: aligning blocks with existing field patterns and contours rather than cutting across them, keeping a set-back from public rights of way, planting or reinforcing hedgerows on the visible flanks, and agreeing a colour and finish for gutters and end-walls. Stating a maximum block height as a condition helps as well, because it removes the fear that tunnels grow taller at each replacement.

Surface water running off impermeable covers

A tunnel roof is impermeable. Rain lands on it and runs to the gutter line rather than soaking into the crop rows, and concentrated flows at the low end of a block cause the erosion and flooding complaints that bring neighbours to the council.

Set out the calculation in a Drainage Strategy: the covered area, the design rainfall event with a climate change allowance from the Environment Agency's published figures, the discharge route, and the attenuation or infiltration provided. Grassed swales between blocks, infiltration trenches along the gutter lines and sediment traps before any discharge to a ditch are the usual answers. Where the holding drains to an ordinary watercourse, consent from the lead local flood authority is a separate approval.

If the site is in Flood Zone 2 or 3, a Flood Risk Assessment becomes a validation requirement, and you will need to show that the tunnels do not displace flood water onto neighbours. Water storage reservoirs for irrigation often appear in the same application, and they carry their own consenting route.

Access, packhouses and vehicle movements

Tunnels rarely come alone. The crop needs cooling, grading and loading, which means a packhouse, hardstanding, a weighbridge sometimes, and articulated lorries on a lane built for tractors.

Deal with the traffic honestly. Give the peak-week movements rather than an annual average, since a soft fruit holding may run four to eight lorries a day for six weeks and almost none in February. Show the access geometry, the visibility in both directions against recorded speeds, and where two lorries pass. A Transport Statement covers a holding of this scale; the larger thresholds that pull in a full Transport Assessment are 50 or more dwellings or 2,500 m² or more of floorspace, which horticultural buildings can reach once packing and cold store are included.

Seasonal worker accommodation as a linked issue

Picking is seasonal, labour is housed on site, and caravans are the usual answer. Part 5 of the GPDO and the Caravan Sites and Control of Development Act 1960 site licensing regime interact here, and councils increasingly want the accommodation dealt with in the same application as the tunnels rather than arriving as a retrospective case two seasons later.

Say how many workers, for how many weeks, in what form of accommodation, with what foul drainage and water supply, and what happens to the units out of season. Permission for tunnels does not carry permission to house people, and that is the single most common enforcement complaint on expanding holdings.

Presenting a horticultural application

The case is agricultural need, landscape response, and drainage control, in that order. Put the need first because it is the policy hook that outweighs the landscape harm, and evidence it with the crop rotation, the yield rationale for protected cropping, the market requirement for extended season and the reason the specific field is suitable.

A Planning Statement should carry:

1. The holding: area, tenure, current cropping, existing built development.
2. The proposal: block layout, hoop specification, anchoring detail, covered area in hectares, cover and uncover periods.
3. Agricultural justification, including why open-field cropping will not achieve it.
4. Landscape assessment and the mitigation offered as conditions.
5. Drainage calculations and the discharge route.
6. Access, movements and any packing or storage buildings.
7. Any accommodation, drainage and licensing.

Illustrative example: a 40-hectare fruit holding proposing 3.2 hectares of tunnels across four blocks, with covers on from March to October. The application that succeeded aligned blocks with existing hedgerows, set a 20 m buffer from the bridleway on the western boundary, offered a condition capping hoop height at 3.5 m, and provided infiltration trenches sized on measured rates. The landscape officer's objection was withdrawn after the block nearest the ridge was dropped.

Enter your postcode on PlanScope to see which of the 66 report types a horticultural application on your holding is likely to need.

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.