Industry News · Ziyang Bozong Greenhouse Industry Co., Ltd.
Two quotes for the same growing area can differ by half, and the honest explanation is rarely that one supplier is greedy. It is that the two numbers describe different buildings, different scopes, or different denominators.
This is a guide to reading a commercial greenhouse cost properly — what the number is made of, what is usually left out, and what to ask so that two quotes can actually be compared.
Almost every quotation is expressed per square metre of covered area. Buyers compare those figures directly, and that is where the confusion starts.
Covered area is not the same as growing floor. A block of single-span tunnels spends a share of its area on end walls and on the strips of ground between houses; a gutter-connected multi-span house spends almost none. For the same covered area, the multi-span house gives more plant space, so its cost per square metre of growing floor can be lower even when its cost per square metre of structure is higher.
Before comparing two prices, check which area each one is divided by.
A greenhouse frame quotation normally covers:
If two suppliers both quote "structure", the difference between them is usually in this list rather than in the price per kilogram.
This is the part that makes cheap quotes look cheap:
Ask for a line-by-line scope before comparing totals. A quote that excludes three of these items is not cheaper, it is smaller.
Span and height. Steel quantity follows these two numbers more than any other. A taller, wider house carries more load and more material.
Galvanizing. Hot-dip after fabrication costs more than pre-galvanized coil, and it is the difference between a frame that lasts and a frame that rusts at every cut and hole.
Covering. Film, polycarbonate and glass sit at very different points on the price scale, and they also change the frame, because each adds different weight and fixing.
Ventilation. Manual roll-up is the cheapest opening. Motorised ridge vents add drives, wiring and controls, and they add a maintenance item.
Site conditions. Wind and snow load, soil, access for a container truck and the distance from the port all show up in the final number without appearing in any brochure.
Erection is often quoted separately, and it should be. A multi-span house is assembled by a crew with the right lifting gear, in a sequence that protects the coating and keeps the frame square. Trying to save this line by using an untrained local crew usually costs more in bent members and re-work than it saves.
Ask who is responsible for alignment, bolt torque and the final inspection, and get it in writing.
The cheapest components to buy are rarely the cheapest to own. The gutter is the clearest example: it holds water, it carries the roof, and it is the first part to corrode. Replacing a gutter means taking the cover off, so a saving at order becomes a large repair in year six.
The same logic applies to fixings. An aluminium profile with a proper locking channel costs more than clips, and it holds the film without point loads. Clips are where tears start.
Put both offers side by side against the same list, and mark each line as included, excluded or unclear:
| Item | Check | |---|---| | Steel section and wall thickness | Stated in mm, per member | | Galvanizing | Hot-dip or pre-galvanized, coating in μm | | Gutter | Thickness, galvanized after forming, slope | | Foundation | Brackets included, civil works excluded? | | Covering | Included or not, which grade | | Openings | Manual or motorised, area per house | | Screens and shade | Included or not | | Installation | Included, supervised or bare frame | | Freight and packing | Which port, which terms | | Warranty | Structural and corrosion, stated separately |
Any row left blank is a risk, not a saving.
Purchase price is one line of a longer account. The rest is cover replacement, screens, drive maintenance and corrosion repair. A house with a heavier frame and a better coating usually costs less per year of service even when it costs more on day one — which is why we state service life and warranty separately instead of quoting a single "lifetime" figure.
Because it would be wrong for your site. The same drawing on a coastal plot with high wind load and a sheltered inland plot with none are not the same product, and a number quoted without those inputs is a guess dressed as a price.
What we do instead: set span, bay and height from your site, state the wind and snow loads in the quotation, and price the scope you actually asked for.
Usually because it covers half the scope — no foundation, no covering, no installation, or a lighter frame. Compare line by line before comparing totals.
Not automatically. Film has the lowest purchase price and the shortest life. Whether it is cheapest per year depends on the replacement cost, including the labour to fit it.
Often yes, because design, drawings and freight are spread over more area. The saving is real but it flattens out, and it does not compensate for a frame that is undersized for the site.
Ziyang Bozong Greenhouse Industry Co., Ltd. manufactures hot-dip galvanized greenhouse structures and agricultural accessories for commercial growers. Agricultural investment guidance is published by the Food and Agriculture Organization; horticultural extension material is published by Penn State Extension.
