Journal · 2026.08 · 8 min
Typhoon Losses: Where a Greenhouse Usually Fails First
Greenhouses rarely blow down in one piece. Post-storm surveys show damage starting at a handful of fixed weak points: film fixings loosen first, wind pours in through an unsealed opening, joints work loose — and only then does the frame itself go. Here is where greenhouses fail first, and what can still be done before landfall.
Every typhoon season ends with “damaged facilities” in the agricultural-loss statistics. But walk a damaged site and you rarely find a greenhouse that blew down in one piece — most damage starts somewhere small and is amplified by sustained wind: a corner of film tears, wind pours in, the roof is pried outward from inside, and only then does the frame deform. Typhoon damage has a sequence, and the first link is usually something too small to notice on an ordinary day.
Wind pressure scales with the square of wind speed — double the speed, four times the pressure. In a typhoon the loads on a greenhouse are pushed to many times their everyday level, and any loose fixing or aged batten can become the first link in the failure chain. Below, ordered the way post-storm surveys usually find them, are the places greenhouses fail first — and what to check for each.
The Breach Starts at the Film: Battens and Fixings
Greenhouse film is rarely “blown through” — it is torn. Film is held to the frame by lock channels, spring wire, and battens; once any run comes loose, wind lifts a corner and the film starts to flap. The stress concentration of repeated flapping can grow a small opening into a full-sheet tear within minutes. The large torn roofs you see after a storm usually began as one short run of rusted spring wire.
- Aged film that has lost tension balloons and flaps in wind — the precursor to tearing.
- Rusted, fatigued spring wire in the lock channel loses grip and lets go first in high wind.
- Loose battens and screws, and old tape repairs, are stress-concentration points.
- Film edges at gutters and ridges are the most common starting points for tears.
Once Wind Gets Inside, Damage Accelerates: Doors, Roll-ups, Vents
The second common starting point is an opening. A door not latched, a roll-up side wall stopped half-open, a vent that no longer seals — one opening on the windward side lets wind pressurise the interior, and that internal pressure stacks on the suction over the outside of the roof, prying the roof off from within. In many cases where a whole roof went, the problem was not the roof — it was one unsealed door.
The roll-up mechanism itself is a weak point: the roll tube is fixed only at its ends and can be pulled out of its track in gusts. Before a typhoon, roll the side walls all the way down, lock them, and add battens or rope — that does more than any improvised bracing afterwards.
Joints Loosen Before Members Bend: Frame and Foundation
Frame failure almost always starts at the connections: purlin-to-frame connectors, rusted and loosened bolts and self-tapping screws, gutter seams. Once these loosen, load paths change — wind load the whole frame used to share concentrates onto a few members, and bending follows. For simple film tunnels the classic failure is different: whole rows pulled out of the ground, because the pipes were embedded too shallow and there were no ground anchors.
- Bolts and connectors whose galvanising has worn through — white rust turning red — have already lost clamping force.
- Loose purlin (C-channel) to main-frame connections are a common start of roof deformation.
- Simple tunnels with shallow pipe embedment and no anchors pull out row by row under uplift.
- Leaky, corroded gutter seams are a structural and a drainage weak point at once.
What You Can Still Do in the Last 72 Hours
Once the warning is out you can no longer strengthen the structure — but you can remove the first link of the failure chain: close and seal every opening, walk every channel and batten one last time, clear gutters and drainage paths, and put away anything around the site that can fly. If the film was due for replacement next year anyway, deliberately cutting it open to let wind pass and save the frame — the film-sacrifice move — is a last resort worth agreeing with your builder in advance.