SYSTEM 02 · SINGLE-SPAN TUNNEL
The single-span tunnel: the least steel per square metre you can build.
A row of arches, no gutters, film down to the ground or to a low rail. Cheapest frame per m², fastest to erect, and the standard answer for season extension, berries and nursery stock. 6.2 and 8.5 m are the two widths we quote most.
A tunnel removes the gutter, which removes a member, a bracket and a post line. That is why the frame price per m² is the lowest in the range. The trade-off is that a tunnel has no internal gutter to walk under and no ridge vent unless you add one, so ventilation is side roll-up or nothing.
| Config | Span | Arch | Arch spacing | Ridge height | Side |
|---|---|---|---|---|---|
| TN-620 | 6.2 m | Ø60.3×1.8 or 30×60×1.8 | 2.0–2.5 m | 3.6 m | film to ground |
| TN-850 | 8.5 m | Ø60.3×2.0 or 30×70×2.0 | 2.0–2.5 m | 4.0 m | film to rail |
Reference shapes. Arch spacing drives wind behaviour more than the section does; do not stretch it without your engineer.
Tunnel or multi-span?
| Question | Tunnel | Multi-span |
|---|---|---|
| Capital per m² | Lowest | 10–25 % higher |
| Internal working space | Single aisle | Gutter lines, better circulation |
| Ventilation | Side roll-up | Ridge + side |
| Snow shedding | Curved roof sheds well | Gutter can pond if blocked |
| Best for | Berries, nursery, season extension | Vegetables at scale, year-round |
Read next
Pages that answer the question this page raises.
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- 06.04StrawberryStrawberry greenhouse and tunnel structure: table-top support loads, gutter systems, vent →
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- 08.04Wind loadGreenhouse wind load: pressure and uplift, exposure, bracing, anchors and the open-side ca→
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Quote a tunnel against your run length
Send the width, the length of each run, the number of runs, and the wind figure. Tunnels are priced per arch and per metre of run.