This house is a multi span film greenhouse with a raised roof section for ventilation and a hydroponic growing layout under the same frame. The raised section gives warm air a continuous way out along the ridge, and the bay is left clear so channels, tanks and the return pipework can be laid out to the crop. The frame is hot dip galvanized steel, bolted rather than welded on site. 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.
A house that is going to run a hydroponic crop has two problems to solve at the same time. The growing system needs a bay that is clear enough to lay out in, and the plants need air moving over them because there is no soil to buffer either the temperature or the water. The roof and the growing layout have to be chosen together for that reason.
A section of the roof is lifted above the line of the house and opens along its length. Warm air inside is lighter than the air outside, so it rises and leaves through that opening without a fan, and because the opening runs continuously rather than at intervals, the exhaust is spread over the whole building instead of being concentrated at one end of it.
That matters more in a hydroponic house than in a soil one. There is no soil to hold water and moderate the temperature, so the crop responds to the air it is in within the same cycle. A raised section along the ridge keeps that air changing through the middle of the day, when the layer under the roof is at its warmest and the plants are working hardest. Houses of this family are grouped on the sawtooth greenhouse range page on this site.
A hydroponic house is laid out around the growing lines. Channels, tanks, the feed and the return are set to the crop and worked from a walkway, with the frame holding the cover and the trellis above them. Because the bay is clear of posts, a line 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 what maintenance means. In a soil house a mistake is buffered; in a hydroponic house the solution reaches the crop within the same cycle, so the tanks, the dosing and the return are checked on a schedule rather than when something looks wrong. A house built on the same principle for a wider crop range is described in the large gothic structure house for farms.
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. The raised roof section is part of the frame geometry rather than an addition bolted on afterwards, which is why the house goes up as one structure.
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 gothic house with roll up sides is described in the gothic arch house with roll up sides.
The table below is the standard build. Span, length, height, cover and the growing layout 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 | Gothic arch roof with a raised ridge vent section, multi span |
| Growing layout | Hydroponic channels, tanks and return pipework under the frame |
| Cooling | Fan and pad cooling system optional |
| Crops | Leafy vegetables, tomato, cucumber, herbs and flowers |
| Customisation | Span, length, height, cover and growing layout 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 arches and the raised section go up together, the film is pulled over and tensioned from the ridge down, and the growing system is set out once the house is closed.
Maintenance divides into the structure, the air and the water. The ridge opening, the side openings and their gear are checked and greased before the season turns. On the water side the tanks, filters and return are cleaned on a cycle, because a blocked filter turns a controlled house into a manual one with no warning. Film tension is checked after the first season and the cover renewed on a planned cycle.
Houses of this type are used for leafy vegetable production in channels, for tomato and cucumber crops on a recirculating system, and for herbs and flowers grown to a controlled schedule. They suit growers who are moving from soil to a hydroponic layout, farms that want the growing system and the house specified together, and operations that expect to add cooling, lighting or a control layer to the same frame later.
Research and extension material on protected crop production, including work on soilless growing and on the growing environment under cover, is published by the Food and Agriculture Organization. Agricultural news and market reporting for commercial growers is published by Farmer's Weekly SA. The specification that matters is the one that still suits the crop ten years from now.
They clear different layers. The raised section takes the warmest air out from under the ridge along the whole length of the house, and the side openings bring the intake down to crop height. Opening more at the side does not reach the layer under the roof.
The frame stays the same, but the layout does set the clearance. Channels, tanks and the return have to run under the frame and be reached from a walkway, so the growing system is usually drawn alongside the house before the span and the height are fixed.
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.
