This house is a multi span film greenhouse laid out for hydroponic vegetable production, with the roof running on arches over a clear bay so that gutters, channels and growing lines can be set to the crop rather than to the structure. The frame is hot dip galvanized steel, bolted rather than welded on site, and the cover is a three layer compressed PE film. Spans run from 8 m to 12 m and the length is set anywhere from 10 m to 100 m, which is what allows a gutter connected block to be built up bay by bay.
In a multi span house the roof does more than cover the crop: it sets the height available over the growing lines and the way water leaves the building. Both of those matter more in hydroponic production than in soil, because the growing lines are fixed and the water is recirculated rather than allowed to drain away.
An arched roof over a wide bay puts the greatest headroom at the centre of the span, where the trusses are, and carries the gutter at the wall line between bays. That gives a clear height over the middle of the bay for growing lines, lamps and trellis, and it gives the house a defined gutter to run water into rather than a roof that sheds onto the crop.
The bay width and the post spacing are set together, because a wider bay needs a deeper truss and that is what decides the clear height at the eaves. Houses of this family are grouped on the film greenhouse range page on this site.
A hydroponic house is laid out around the growing lines. Channels, gutters, tanks and the return pipework are set to the crop and worked from a walkway, and the frame is there to hold the cover and the trellis above them. Because the bay is clear of posts, the lines can run the full length of the house instead of breaking around a column, which is what keeps a recirculating system simple to lay out and simple to service.
It also changes the maintenance priority. In a soil house the soil buffers a mistake; in a hydroponic house the nutrient solution reaches the crop within the same cycle, so the tanks, the return and the dosing are the parts that get checked on a schedule. A house built on the same principle for tomato and cucumber crops is described in the gothic multi span poly film 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. Columns and trusses are bolted rather than welded on site, which leaves the coating intact and lets a damaged member be unbolted and replaced instead of cut out. A gutter connected layout joins the bays along the gutter line, so one block shares its downpipes instead of every bay shedding on its own.
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 using the same cover in a soilless layout is described in the soilless film house for tomato growing.
The table below is the standard build. Span, length, height and cover 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 | Arched roof, multi span, gutter connected between bays |
| Growing layout | Hydroponic channels, tanks and return pipework under the frame |
| Gutters | Galvanized gutters between bays with downpipes |
| Crops | Leafy vegetables, tomato, cucumber and other greenhouse crops |
| Customisation | Span, length, height and cover set to the site and the crop |
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 arches and trusses go up bay by bay and the gutters are levelled across the block as the bays are joined, and the film is pulled over last.
Maintenance divides into the frame, the water and the cover. The gutter line and the downpipes are cleared before the wet season, because a blocked outlet backs water into the bay rather than away from it. On a hydroponic house the tanks, dosing and return are checked on the same cycle as the crop, and the film is inspected after the first season and renewed on a planned cycle.
Houses of this type are used for hydroponic leafy vegetable production, for tomato and cucumber crops, and for growers who want a multi span house with a clear bay to lay out growing lines in. They suit farms that are moving from soil to a recirculating system, blocks that are being extended bay by bay on the gutter line, and operations that expect to add cooling, lighting or a control system to the same frame later.
Standards and published guidance for horticultural structures and for the materials used in them are published by NEN. Production and market reporting on indoor and vertical growing is published by VerticalFarmDaily. The specification that matters is the one that still suits the crop ten years from now.
Because a multi span bay is clear of posts, the growing lines can run the full length of the house and the tanks and return pipework sit under the frame rather than around it. Film keeps the build cost down, and the money that is not spent on the cover goes into the growing system.
The truss. A wider bay needs a deeper truss to carry the roof and the cover, and the clear height at the eaves is what is left after that, so span and post spacing are set together rather than chosen separately.
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 the growing layout you intend to run. We reply with a layout drawing and a full quotation.
