This house is a tunnel type film greenhouse built for tomato production at commercial scale, on a hot dip galvanized steel frame with a three layer compressed PE film cover. The bay is clear of internal posts, so tomato rows run the length of the house and the crop can be worked and picked without breaking around a column. Spans run from 8 m to 12 m and the length is set anywhere from 10 m to 100 m, or built to client demand, which is what allows a farm to add to the block one bay at a time.
Tomato is a crop that rewards a house with a clear bay and punishes one that holds warm air over the canopy. Both come back to the same decision: how wide the span is and where the air can leave. A tunnel with the right openings runs a tomato crop from the first truss to the last without the plants closing down in the afternoon.
Tomato is grown on rows, and rows want to run the length of the bay without breaking around a post. A tunnel span is clear from wall to wall, so row spacing is set by the crop and the picking trolley rather than by the structure, and the same house can be worked on both sides of every row. It also keeps each house a separate environment, which is useful when one block is being turned over between crops.
The film cover is the reason a tunnel is affordable at farm scale. It costs less than a rigid cladding and it can be replaced on a planned cycle, so a grower can put the money into the crop and the irrigation rather than into the structure. Houses of this family are grouped on the tunnel greenhouse range page on this site.
A tomato canopy closes over the rows within a few weeks of planting, and once it closes the air inside it stops moving on its own. That layer is warmer and more humid than the rest of the bay, which is the condition that favours leaf mould and botrytis after the evening irrigation, and it is also where pollination slows once the afternoon turns hot.
Opening the gable and the side walls brings the intake down to crop height, so the air that enters has to cross the canopy on its way to the outlet instead of passing over the top of it. That is what keeps the fruit set going through the heat of the day and keeps the leaves dry into the evening. A tunnel house built for the same crop with a galvanized frame is described in the agricultural film tunnel house for tomatoes and vegetables.
The frame is hot dip galvanized steel, galvanized after the sections are formed, so the zinc reaches the bore of the tubes, the cut ends and the inside of every drilled hole. Hoops, purlins and the base rail are bolted rather than welded on site, which leaves the coating intact and lets a bent hoop be unbolted and replaced instead of cut out.
The cover is a three layer compressed PE film. The layers carry their additives separately, so the anti condensation face keeps working for longer than a single layer sheet does, and the outer layer carries the UV stabiliser. Film is held on the hoops and the base rail with clips, which means a panel can be released and retensioned without a full recover. A house on the same frame built for a wider crop range is described in the farm tunnel house for tomato and vegetable growing.
The table below is the standard build. Span, length, height, cover and openings are set to the site and to the crop.
| Greenhouse span | 8 m / 9 m / 10 m / 11 m / 12 m |
| Greenhouse length | 10 m to 100 m, or built to client demand |
| Greenhouse height | 3 m to 8 m, or custom |
| Structure material | Hot dip galvanized steel pipe, bolted assembly |
| Cover material | Three layer compressed PE film |
| Roof type | Arch roof, multi span tunnel with no internal posts |
| Ventilation | Gable openings and side wall openings at crop height |
| Cooling | Fan and pad cooling system optional |
| Crops | Tomato, cucumber, leafy vegetables, fruit and flowers |
| Customisation | Span, length, height, cover and openings set to the site |
The kit arrives formed and drilled with the fittings, so the work on site is bolting and tensioning rather than fabrication and no welding is done at any point. Ground posts or a base rail are set to the drawing first, the hoops and purlins go up bay by bay, and the film is pulled over and tensioned from the ridge down before the side openings are fitted.
Maintenance is mostly about the film and the openings. The side wall gear and the gable openings are the working parts, so they are checked and greased before the season turns. Film tension is checked after the first season and the cover renewed on a planned cycle, while the galvanized frame runs for far longer than the film does.
Houses of this type are used for tomato and cucumber production, for leafy vegetables and for fruiting crops grown in soil or in bags on the floor of the bay. They suit commercial tomato growers who run a block of houses through the season, farms that are extending a tunnel range one bay at a time, and operations that expect to add irrigation, cooling or a control system to the same frame later.
Research and extension material on protected crop production, including work on the growing environment under cover, is published by NC State University through its horticultural science department. Market and price reporting for commercial growers is published by Agriwatch. The specification that matters is the one that still suits the crop ten years from now.
Because once the canopy closes, the air inside it stops moving on its own. The side openings bring air in at that height so it crosses the leaves rather than passing over the top of them, which is what keeps fruit set going through the afternoon.
It is set by how the crop is trained. Tomatoes grown on strings to a layering system need the height at the gutter for the trusses and the working space above them, and the span and post spacing are then chosen together to give it.
The galvanized steel frame is rated for 15 to 20 years under normal growing conditions. The film cover runs on a shorter cycle than the frame, typically 3 to 5 years depending on UV exposure at the site.
We provide a 10 year structural warranty and a 5 year anti-corrosion warranty on the galvanized frame. Details are set out in the contract for each project.
Send your site dimensions, the crops you plan to grow and your local wind, snow and rain figures. We reply with a layout drawing and a full quotation.
