This house puts three things into one structure. The frame is a gothic arch carried on a multi span line, so the roof is steeper than a round arch and the house can be built wide without a run of internal posts. Inside it the crop is grown hydroponically, with the feed run to the beds and the seedling benches on wheels so they can be moved out of the way. Cooling, heating and ventilation are handled by the control layer rather than a person walking the house. The result is a block that can be run through the year on a set schedule instead of following the weather.
Building a house wide and building it tall are two different problems. A multi span gothic house answers both at once, because the arch is carried across each bay and the bays are joined along a gutter line, so the width comes from repeating a span rather than from stretching one. That is what makes a block of this size practical to ventilate, to cover and to work inside.
The structure is hot dip galvanized steel, supplied in spans of 8 m to 12 m, in lengths from 10 m to 100 m or set to the site, with a working height of 3 m to 8 m. Galvanizing is applied after the tubes are formed and drilled, so cut ends and bolt holes carry the same coating and no secondary treatment is needed on site.
The repeat is the useful part. A grower who has run one bay knows what the next one costs, the gutter line carries the water rather than shedding it into a walkway, and a block can be extended along the same line when the market asks for more. Houses of this arrangement are grouped on the multi span greenhouse range page on this site.
The crop is grown without soil. The feed is mixed and dosed at a set point and delivered to the beds, with the run-off collected rather than drained, and because the root zone is a defined volume instead of a field, the water and the nutrients can be held to a figure rather than estimated. On tomato this matters most at the start of the season, where an even root zone gives an even first truss and the picking dates hold together.
The seedling benches move. Raising the young plants on wheeled benches means the house can be closing down one row while the next is being set out, and a block of benches can be rolled to the end for transplanting instead of carried. Because the cover is a film, the whole block stays on the same light level and the crop does not vary between the edges and the middle. A house of the same family covered in poly film is described in the gothic multi span poly film greenhouse page.
Cooling, heating and ventilation are run from one control layer. Roof and side vents open in stages as the house warms, the circulation fans move air along the block so the crop at the far end is not working in air the near end has already used, and the fan and pad set takes the peak out of the middle of the day. Heating is called on when the night temperature falls below the set point rather than on a timer.
Shading and irrigation can be added to the same controller, which is what turns a set of individual systems into a house that runs to a schedule. The gain is less in the equipment than in the labour: a block of this size no longer needs someone walking it to open and close vents through the day.
The table below is the standard build. Span, length, bay count and the control package are set to the site and to the crop.
| House type | Multi span gothic arch |
| Span | 8 m, 9 m, 10 m, 11 m or 12 m |
| Length | 10 m to 100 m or set to the site |
| Working height | 3 m to 8 m |
| Structure material | Hot dip galvanized steel |
| Cover | PO or PE film, 80 to 200 micron |
| Light transmission | Above 89 per cent |
| Diffusion | About 53 per cent |
| Working temperature | -40 C to 60 C |
| Growing system | Hydroponic beds with recirculating feed |
| Seedling benches | Movable benches on wheels |
| Ventilation | Roof and side vents on staged opening |
| Cooling | Fan and cooling pad |
| Heating | Optional, on a night set point |
| Shading | Optional, on the same controller |
| Automation | Optional intelligent package from shading to irrigation |
| Crops | Tomato, cucumber, vegetables, fruit and flowers |
| Customisation | Span, length, bay count and control package set to the site |
A block of this size is built to a drawing. Ground posts or a base rail are set and levelled first, because the load comes down the gutter columns and the side lines. The bays are raised one at a time, the gutter line and the bracing follow, the end walls are framed, and the cover is fitted after the frame is closed so the film is not worked around while the steel is going up. The hydroponic beds, the seedling benches and the control gear are set out once the house is watertight.
Upkeep divides into structure, crop system and control. Fixings and the cover are checked before the windy season, vents and fan drives are tested at the same time, and the fan and pad set is serviced before the first hot spell rather than during it. On the crop side the beds are cleaned between crops, the filters and dosing gear are serviced on the crop cycle, and the benches are checked for free movement so the wheels do not start to drag.
Blocks of this type are used for year round tomato and cucumber production, for vegetable and leafy crop programmes that need a set delivery date, and for fruit and cut flowers grown under a controlled climate. They suit a grower moving from a field or a single tunnel to a first block, an existing operation adding bays alongside a house already on the site, and projects that plan to bring shading, lighting or full automation in at a later stage.
Standards for greenhouse construction and components are published by DIN. Farming and market reporting for growers in southern Africa is published by Farmer's Weekly SA. A multi span block grown for vegetables and tomatoes is described in the commercial grade multi span greenhouse page.
Because the gutter line does the work. Joined bays shed water into one gutter rather than into the walkway between separate houses, the block is worked as one floor instead of several, and the climate control covers the whole area rather than one tunnel at a time.
No. Each bay carries its own arch across the span, so the floor inside is clear apart from the gutter columns at the join. That is what allows a bed layout or a bench system to be planned across the full width of the block.
The galvanized steel frame is rated for 15 to 20 years under normal growing conditions. The film cover, the vent drives, the fans and the dosing gear run on their own service cycles and are replaced as they come due.
We provide a 10 year structural warranty and a 5 year anti-corrosion warranty on the galvanized steelwork. Details are set out in the contract for each project.
Send your site dimensions, the crop you plan to run and the growing layout you intend to use. We reply with a layout drawing and a full quotation.
